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despite extensive efforts, to date only two quasars have been found at z > 7, due to a combination of low spatial density and high contamination from more ubiquitous galactic cool dwarfs in quasar selection. this limits our current knowledge of the super-massive black hole growth mechanism and reionization history. in this letter, we report the discovery of a luminous quasar at z = 7.021, dels j003836.10-152723.6 (hereafter j0038-1527), selected using photometric data from dark energy spectroscopic instrument legacy imaging survey, pan-starrs1 (ps1) imaging survey, as well as wide-field infrared survey explore mid-infrared all-sky survey. with an absolute magnitude of m 1450 = -27.1 and bolometric luminosity of l bol = 5.6 × 1013 l ⊙, j0038-1527 is the most luminous quasar known at z > 7. deep optical to near-infrared spectroscopic observations suggest that j0038-1527 hosts a 1.3 billion solar mass black hole accreting at the eddington limit, with an eddington ratio of 1.25 ± 0.19. the c iv broad emission line of j0038-1527 is blueshifted by more than 3000 km s-1 relative to the quasar systemic redshift. more detailed investigations of the high-quality spectra reveal three extremely high-velocity c iv broad absorption lines with velocity from 0.08 to 0.14 times the speed of light and total “balnicity” index of more than 5000 km s-1, suggesting the presence of relativistic outflows. j0038-1527 is the first quasar found at the epoch of reionization with such strong outflows, and therefore provides a unique laboratory to investigate active galactic nuclei feedback on the formation and growth of the most massive galaxies in the early universe. | the discovery of a luminous broad absorption line quasar at a redshift of 7.02 |
we present the results of 15 years of monitoring lensed quasars, which was conducted by the cosmograil programme at the leonhard euler 1.2 m swiss telescope. the decade-long light curves of 23 lensed systems are presented for the first time. we complement our data set with other monitoring data available in the literature to measure the time delays in 18 systems, among which nine reach a relative precision better than 15% for at least one time delay. to achieve this, we developed an automated version of the curve-shifting toolbox pycs to ensure robust estimation of the time delay in the presence of microlensing, while accounting for the errors due to the imperfect representation of microlensing. we also re-analysed the previously published time delays of rx j1131-1231 and he 0435-1223, by adding six and two new seasons of monitoring, respectively, and confirming the previous time-delay measurements. when the time delay measurement is possible, we corrected the light curves of the lensed images from their time delay and present the difference curves to highlight the microlensing signal contained in the data. to date, this is the largest sample of decade-long lens monitoring data, which is useful to measure h0 and the size of quasar accretion discs with microlensing as well as to study quasar variability. all light curves presented in this paper are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/640/a105 | cosmograil. xix. time delays in 18 strongly lensed quasars from 15 years of optical monitoring |
the sloan digital sky survey reverberation mapping (sdss-rm) project is a dedicated multi-object rm experiment that has spectroscopically monitored a sample of 849 broad-line quasars in a single 7 deg2 field with the sdss-iii baryon oscillation spectroscopic survey spectrograph. the rm quasar sample is flux-limited to i psf = 21.7 mag, and covers a redshift range of 0.1 < z < 4.5 without any other cuts on quasar properties. optical spectroscopy was performed during 2014 january-july dark/gray time, with an average cadence of ~4 days, totaling more than 30 epochs. supporting photometric monitoring in the g and i bands was conducted at multiple facilities including the canada-france-hawaii telescope (cfht) and the steward observatory bok telescope in 2014, with a cadence of ~2 days and covering all lunar phases. the rm field (r.a., decl. = 14:14:49.00, +53:05:00.0) lies within the cfht-ls w3 field, and coincides with the pan-starrs 1 (ps1) medium deep field md07, with three prior years of multi-band ps1 light curves. the sdss-rm six month baseline program aims to detect time lags between the quasar continuum and broad line region (blr) variability on timescales of up to several months (in the observed frame) for ~10% of the sample, and to anchor the time baseline for continued monitoring in the future to detect lags on longer timescales and at higher redshift. sdss-rm is the first major program to systematically explore the potential of rm for broad-line quasars at z > 0.3, and will investigate the prospects of rm with all major broad lines covered in optical spectroscopy. sdss-rm will provide guidance on future multi-object rm campaigns on larger scales, and is aiming to deliver more than tens of blr lag detections for a homogeneous sample of quasars. we describe the motivation, design, and implementation of this program, and outline the science impact expected from the resulting data for rm and general quasar science. | the sloan digital sky survey reverberation mapping project: technical overview |
we present an analysis of the nuclear variability of ∼28,000 nearby (z < 0.15) galaxies with sloan digital sky survey (sdss) spectroscopy in stripe 82. we construct light curves using difference imaging of sdss g-band images, which allows us to detect subtle variations in the central light output. we select variable active galactic nuclei (agns) by assessing whether detected variability is well-described by a damped random walk model. we find 135 galaxies with agn-like nuclear variability. while most of the variability-selected agns have narrow emission lines consistent with the presence of an agn, a small fraction have narrow emission lines dominated by star formation. the star-forming systems with nuclear agn-like variability tend to be low mass (m * < 1010 m ⊙), and may be agns missed by other selection techniques due to star formation dilution or low metallicities. we explore the agn fraction as a function of stellar mass, and find that the fraction of variable agn increases with stellar mass, even after taking into account the fact that lower-mass systems are fainter. there are several possible explanations for an observed decline in the fraction of variable agn with decreasing stellar mass, including a drop in the supermassive black hole occupation fraction, a decrease in the ratio of black hole mass to galaxy stellar mass, or a change in the variability properties of lower-mass agns. we demonstrate that optical photometric variability is a promising avenue for detecting agns in low-mass, star formation-dominated galaxies, which has implications for the upcoming large synoptic survey telescope. | identifying agns in low-mass galaxies via long-term optical variability |
we present the results of a systematic search for quasars in the catalina real-time transient survey exhibiting both strong photometric variability and spectroscopic variability over a decadal baseline. we identify 111 sources with specific patterns of optical and mid-infrared photometric behaviour and a defined spectroscopic change. these 'changing-state' quasars (csqs) form a higher luminosity sample to complement existing sets of 'changing-look' agns and quasars in the literature. the csqs (by selection) exhibit larger photometric variability than the changing-look quasars (clqs). the spectroscopic variability is marginally stronger in the csqs than clqs as defined by the change in h β/[o iii] ratio. we find 48 sources with declining h β flux and 63 sources with increasing h β flux, and discover 8 sources with z > 0.8, further extending the redshift arm. our csq sample compares to the literature clq objects in similar distributions of h β flux ratios and differential eddington ratios between high (bright) and low (dim) states. taken as a whole, we find that this population of extreme varying quasars is associated with changes in the eddington ratio and the time-scales imply cooling/heating fronts propagating through the disc. | understanding extreme quasar optical variability with crts - ii. changing-state quasars |
we present iram/noema and jvla observations of the quasar j1342+0928 at z = 7.54 and report detections of copious amounts of dust and [c ii] emission in the interstellar medium (ism) of its host galaxy. at this redshift, the age of the universe is 690 myr, about 10% younger than the redshift of the previous quasar record holder. yet, the ism of this new quasar host galaxy is significantly enriched by metals, as evidenced by the detection of the [c ii] 158 μm cooling line and the underlying far-infrared (fir) dust continuum emission. to the first order, the fir properties of this quasar host are similar to those found at a slightly lower redshift (z∼ 6), making this source by far the fir-brightest galaxy known at z≳ 7.5. the [c ii] emission is spatially unresolved, with an upper limit on the diameter of 7 kpc. together with the measured fwhm of the [c ii] line, this yields a dynamical mass of the host of < 1.5× {10}11 {m}⊙ . using standard assumptions about the dust temperature and emissivity, the noema measurements give a dust mass of (0.6{--}4.3)× {10}8 {m}⊙ . the brightness of the [c ii] luminosity, together with the high dust mass, imply active ongoing star formation in the quasar host. using [c ii]-sfr scaling relations, we derive star formation rates of 85-545 {m}⊙yr-1 in the host, consistent with the values derived from the dust continuum. indeed, an episode of such past high star formation is needed to explain the presence of ∼108 m ⊙ of dust implied by the observations. | copious amounts of dust and gas in a z = 7.5 quasar host galaxy |
we present a tomographic weak lensing analysis of the kilo degree survey data release 4 (kids-1000), using a new pseudo angular power spectrum estimator (pseudo-cℓ) under development for the esa euclid mission. over 21 million galaxies with shape information are divided into five tomographic redshift bins, ranging from 0.1 to 1.2 in photometric redshift. we measured pseudo-cℓ using eight bands in the multipole range 76 < ℓ < 1500 for auto- and cross-power spectra between the tomographic bins. a series of tests were carried out to check for systematic contamination from a variety of observational sources including stellar number density, variations in survey depth, and point spread function properties. while some marginal correlations with these systematic tracers were observed, there is no evidence of bias in the cosmological inference. b-mode power spectra are consistent with zero signal, with no significant residual contamination from e/b-mode leakage. we performed a bayesian analysis of the pseudo-cℓ estimates by forward modelling the effects of the mask. assuming a spatially flat λcdm cosmology, we constrained the structure growth parameter s8 = σ8(ωm/0.3)1/2 = 0.754−0.029+0.027. when combining cosmic shear from kids-1000 with baryon acoustic oscillation and redshift space distortion data from recent sloan digital sky survey (sdss) measurements of luminous red galaxies, as well as the lyman-α forest and its cross-correlation with quasars, we tightened these constraints to s8 = 0.771−0.032+0.006. these results are in very good agreement with previous kids-1000 and sdss analyses and confirm a ∼3σ tension with early-universe constraints from cosmic microwave background experiments. | kids and euclid: cosmological implications of a pseudo angular power spectrum analysis of kids-1000 cosmic shear tomography |
we present a study of a luminous, $z\, =\, 0.15$, type-2 quasar ($l_{[\rm o iii]}$ = 1042.8 erg s-1) from the quasar feedback survey. it is classified as 'radio-quiet' ($l_{\mathrm{1.4\, ghz}}$ = 1023.8 w hz-1); however, radio imaging reveals ~ 1 kpc low-power radio jets (pjet = 1044 erg s-1) inclined into the plane of the galaxy disc. we combine muse and alma observations to map stellar kinematics and ionized and molecular gas properties. the jets are seen to drive galaxy-wide bi-conical turbulent outflows, reaching w80 = 1000 - 1300 km s-1, in the ionized phase (traced via optical emission lines), which also have increased electron densities compared to the quiescent gas. the turbulent gas is driven perpendicular to the jet axis and is escaping along the galaxy minor axis, reaching 7.5 kpc on both sides. traced via co(3-2) emission, the turbulent material in molecular gas phase is one-third as spatially extended and has three times lower velocity-dispersion as compared to ionized gas. the jets are seen to be strongly interacting with the interstellar medium (ism) through enhanced ionized emission and disturbed/depleted molecular gas at the jet termini. we see further evidence for jet-induced feedback through significantly higher stellar velocity-dispersion aligned, and co-spatial with, the jet axis ($\lt 5\, ^{\circ }$). we discuss possible negative and positive feedback scenarios arising due to the interaction of the low-power jets with the ism in the context of recent jet-ism interaction simulations, which qualitatively agree with our observations. we discuss how jet-induced feedback could be an important feedback mechanism even in bolometrically luminous 'radio-quiet' quasars. | quasar feedback survey: multiphase outflows, turbulence, and evidence for feedback caused by low power radio jets inclined into the galaxy disc |
understanding the formation and growth of supermassive black holes (smbhs) at high redshift represents a major challenge for theoretical models. in this work, we investigate the early evolution of the first smbhs by constraining their distribution in mass and luminosity at z > 4. in particular, we focus on the poorly explored low-mass end of the nuclear black hole (bh) distribution down to z ≃ 4, and explore its connection with the nature of the first bh seeds and the processes governing their mass growth. to this aim, we have developed cat (cosmic archaeology tool), a new semi-analytic model that describes the formation of the first stars and bhs in a self-consistent way and follows the co-evolution of nuclear bhs and their host galaxies for a representative population at z > 4. we find that current observational constraints favour models where the growth of bh seeds is eddington limited and occurs at the bondi-hoyle-lyttleton rate or where super-eddington accretion occurs via a slim disc during gas-rich galaxy mergers. the main difference between these two model variants lies at the low end of the predicted mass and luminosity functions at 4 ≤ z ≤ 6, where a clear gap appears in the first model, reflecting the stunted growth of light bh seeds formed as remnants of the first stars. detecting this signature will be extremely challenging even for the future generation of space observatories, such as jwst, athena, and lynx. | the low-end of the black hole mass function at cosmic dawn |
bright, high-redshift (z > 6) qsos are powerful probes of the ionization state of the intervening intergalactic medium (igm). the detection of ly α damping wing absorption imprinted in the spectrum of high-z qsos can provide strong constraints on the epoch of reionization (eor). in this work, we perform an independent ly α damping wing analysis of two known z > 7 qsos; desj0252-0503 at z = 7.00 (wang et al.) and j1007+2115 at z = 7.51 (yang et al.). for this, we utilize our existing bayesian framework which simultaneously accounts for uncertainties in: (i) the intrinsic ly α emission profile (reconstructed from a covariance matrix of measured emission lines; extended in this work to include n v) and (ii) the distribution of ionized (h ii) regions within the igm using a 1.63 gpc3 reionization simulation. this approach is complementary to that used in the aforementioned works as it focuses solely redward of ly α (1218 < λ < 1230 å) making it more robust to modelling uncertainties while also using a different methodology for (i) and (ii). we find, for an eor morphology driven by galaxies within mh ≳ 109 m⊙ haloes, $\bar{x}_{\mathrm{h\, {\scriptscriptstyle i}}{}} = 0.64\substack{+0.19 \-0.23}$ (68 per cent) at z = 7 and $\bar{x}_{\mathrm{h\, {\scriptscriptstyle i}}{}} = 0.27\substack{+0.21 \-0.17}$ at z = 7.51 consistent within 1σ to the previous works above, though both are slightly lower in amplitude. following the inclusion of n v into our reconstruction pipeline, we perform a reanalysis of ulasj1120+0641 at z = 7.09 (mortlock et al.) and ulasj1342+0928 at z = 7.54 (bañados et al.) finding $\bar{x}_{\mathrm{h\, {\scriptscriptstyle i}}{}} = 0.44\substack{+0.23 \-0.24}$ at z = 7.09 and $\bar{x}_{\mathrm{h\, {\scriptscriptstyle i}}{}} = 0.31\substack{+0.18 \-0.19}$ at z = 7.54. finally, we combine the qso damping wing constraints for all four z ≳ 7 qsos to obtain a single, unified constraint of $\bar{x}_{\mathrm{h\, {\scriptscriptstyle i}}{}} = 0.49\substack{+0.11 \-0.11}$ at z = 7.29. | igm damping wing constraints on reionization from covariance reconstruction of two z ≳ 7 qsos |
radio astronomy has changed. for years it studied relatively rare sources, which emit mostly non-thermal radiation across the entire electromagnetic spectrum, i.e. radio quasars and radio galaxies. now, it is reaching such faint flux densities that it detects mainly star-forming galaxies and the more common radio-quiet active galactic nuclei. these sources make up the bulk of the extragalactic sky, which has been studied for decades in the infrared, optical, and x-ray bands. i follow the transformation of radio astronomy by reviewing the main components of the radio sky at the bright and faint ends, the issue of their proper classification, their number counts, luminosity functions, and evolution. the overall "big picture" astrophysical implications of these results, and their relevance for a number of hot topics in extragalactic astronomy, are also discussed. the future prospects of the faint radio sky are very bright, as we will soon be flooded with survey data. this review should be useful to all extragalactic astronomers, irrespective of their favourite electromagnetic band(s), and even stellar astronomers might find it somewhat gratifying. | the faint radio sky: radio astronomy becomes mainstream |
in this paper, multiwavelength data are compiled for a sample of 1425 fermi blazars to calculate their spectral energy distributions (seds). a parabolic function, {{log}}{(ν {f}ν )={p}1({{log}}ν -{p}2)}2+{p}3, is used for sed fitting. synchrotron peak frequency ({log}{ν }{{p}}), spectral curvature (p1), peak flux ({ν }{{p}}{f}{ν {{p}}}), and integrated flux (ν {f}ν ) are successfully obtained for 1392 blazars (461 flat-spectrum radio quasars [fsrqs], 620 bl lacs [bls], and 311 blazars of uncertain type [bcus]; 999 sources have known redshifts). monochromatic luminosity at radio 1.4 ghz, optical r band, x-ray at 1 kev and γ-ray at 1 gev, peak luminosity, integrated luminosity, and effective spectral indices of radio to optical ({α }{{ro}}) and optical to x-ray ({α }{{ox}}) are calculated. the “bayesian classification” is employed to log {ν }{{p}} in the rest frame for 999 blazars with available redshift, and the results show that three components are enough to fit the log {ν }{{p}} distribution; there is no ultra-high peaked subclass. based on the three components, the subclasses of blazars using the acronyms of abdo et al. are classified, and some mutual correlations are also studied. conclusions are finally drawn as follows: (1) seds are successfully obtained for 1392 blazars. the fitted peak frequencies are compared with common sources from available samples. (2) blazars are classified as low synchrotron peak sources if log {ν }{{p}}({hz})≤slant 14.0, intermediate synchrotron peak sources if 14.0\lt {log} {ν }{{p}}({hz})≤slant 15.3, and high synchrotron peak sources if {log} {ν }{{p}}({hz})\gt 15.3. (3) gamma-ray emissions are strongly correlated with radio emissions. gamma-ray luminosity is also correlated with synchrotron peak luminosity and integrated luminosity. (4) there is an anticorrelation between peak frequency and peak luminosity within the whole blazar sample. however, there is a marginally positive correlation for high synchrotron peak bl lacs (hbls), and no correlations for fsrqs or low synchrotron peak bl lacs (lbls). (5) there are anticorrelations between the monochromatic luminosities (γ-ray and radio bands) and the peak frequency within the whole sample and bl lacs. (6) the optical to x-ray ({α }{{ox}}) and radio to optical ({α }{{ro}}) spectral indices are strongly anticorrelated with peak frequency (log {ν }{{p}}) within the whole sample, but the correlations for subclasses of fsrqs, lbls, and hbls are different. | the spectral energy distributions of fermi blazars |
we present an all-sky sample of ≈1.4 million active galactic nuclei (agns) meeting a two-color infrared photometric selection criteria for agns as applied to sources from the wide-field infrared survey explorer final catalog release (allwise). we assess the spatial distribution and optical properties of our sample and find that the results are consistent with expectations for agns. these sources have a mean density of ≈38 agns per square degree on the sky, and their apparent magnitude distribution peaks at g ≈ 20, extending to objects as faint as g ≈ 26. we test the agn selection criteria against a large sample of optically identified stars and determine the “leakage” (that is, the probability that a star detected in an optical survey will be misidentified as a quasi-stellar object (qso) in our sample) rate to be ≤4.0 × 10-5. we conclude that our sample contains almost no optically identified stars (≤0.041%), making this sample highly promising for future celestial reference frame work as it significantly increases the number of all-sky, compact extragalactic objects. we further compare our sample to catalogs of known agns/qsos and find a completeness value of ≳84% (that is, the probability of correctly identifying a known agn/qso is at least 84%) for agns brighter than a limiting magnitude of r ≲ 19. our sample includes approximately 1.1 million previously uncataloged agns. | identification of 1.4 million active galactic nuclei in the mid-infrared using wise data |
in the spring of 2011 we carried out a 2.5 month reverberation mapping campaign using the 3 m shane telescope at lick observatory, monitoring 15 low-redshift seyfert 1 galaxies. this paper describes the observations, reductions and measurements, and data products from the spectroscopic campaign. the reduced spectra were fitted with a multicomponent model in order to isolate the contributions of various continuum and emission-line components. we present light curves of broad emission lines and the active galactic nucleus (agn) continuum, and measurements of the broad hβ line widths in mean and rms spectra. for the most highly variable agns we also measured broad hβ line widths and velocity centroids from the nightly spectra. in four agns exhibiting the highest variability amplitudes, we detect anticorrelations between broad hβ width and luminosity, demonstrating that the broad-line region “breathes” on short timescales of days to weeks in response to continuum variations. we also find that broad hβ velocity centroids can undergo substantial changes in response to continuum variations; in ngc 4593, the broad hβ velocity shifted by ∼250 km s-1 over a 1 month period. this reverberation-induced velocity shift effect is likely to contribute a significant source of confusion noise to binary black hole searches that use multi-epoch quasar spectroscopy to detect binary orbital motion. we also present results from simulations that examine biases that can occur in measurement of broad-line widths from rms spectra due to the contributions of continuum variations and photon-counting noise. | the lick agn monitoring project 2011: spectroscopic campaign and emission-line light curves |
we present reverberation mapping results for the mg ii λ2800 å broad emission line in a sample of 193 quasars at $0.35\lt z\lt 1.7$ with photometric and spectroscopic monitoring observations from the sloan digital sky survey reverberation mapping project during 2014-2017. we find significant time lags between the mg ii and continuum lightcurves for 57 quasars, and define a "gold sample" of 24 quasars with the most reliable lag measurements. we estimate false-positive rates for each lag that range from 1% to 24%, with an average false-positive rate of 11% for the full sample and 8% for the gold sample. there are an additional ∼40 quasars with marginal mg ii lag detections, which may yield reliable lags after additional years of monitoring. the mg ii lags follow a radius-luminosity relation with a best-fit slope that is consistent with $\alpha =0.5$ , but with an intrinsic scatter of 0.36 dex that is significantly larger than found for the hβ radius-luminosity relation. for targets with sdss-rm lag measurements of other emission lines, we find that our mg ii lags are similar to the hβ lags and ∼2-3 times larger than the c iv lags. this work significantly increases the number of mg ii broad-line lags and provides additional reverberation-mapped black hole masses, filling the redshift gap at the peak of supermassive black hole growth between the hβ and c iv emission lines in optical spectroscopy. | the sloan digital sky survey reverberation mapping project: mg ii lag results from four years of monitoring |
we report the spectroscopic follow-up of 175 lensed quasar candidates selected using gaia data release 2 observations following paper iii of this series. systems include 86 confirmed lensed quasars and a further 17 likely lensed quasars based on imaging and/or similar spectra. we also confirm 11 projected quasar pairs and 11 physical quasar pairs, while 25 systems are left as unclassified quasar pairs - pairs of quasars at the same redshift, which could be either distinct quasars or potential lensed quasars. especially interesting objects include eight quadruply imaged quasars of which two have bal sources, an apparent triple, and a doubly lensed lobal quasar. the source redshifts and image separations of these new lenses range between 0.65-3.59 and 0.78-6.23 arcsec, respectively. we compare the known population of lensed quasars to an updated mock catalogue at image separations between 1 and 4 arcsec, showing a very good match at z < 1.5. at z > 1.5, only 47 per cent of the predicted number are known, with 56 per cent of these missing lenses at image separations below 1.5 arcsec. the missing higher redshift, small-separation systems will have fainter lensing galaxies, and are partially explained by the unclassified quasar pairs and likely lenses presented in this work, which require deeper imaging. of the 11 new reported projected quasar pairs, 5 have impact parameters below 10 kpc, almost tripling the number of such systems, which can probe the innermost regions of quasar host galaxies through absorption studies. we also report four new lensed galaxies discovered through our searches, with source redshifts ranging from 0.62 to 2.79. | gravitationally lensed quasars in gaia - iv. 150 new lenses, quasar pairs, and projected quasars |
studying how nuclear star clusters (nscs) form and how they are related to the growth of the central massive black holes (mbhs) and their host galaxies is fundamental for our understanding of the evolution of galaxies and the processes that have shaped their central structures. we present the results of a semi-analytical galaxy formation model that follows the evolution of dark matter halos along merger trees, as well as that of the baryonic components. this model allows us to study the evolution of nscs in a cosmological context, by taking into account the growth of nscs due to both dynamical-friction-driven migration of stellar clusters and star formation triggered by infalling gas, while also accounting for dynamical heating from (binary) mbhs. we find that in situ star formation contributes a significant fraction (up to ∼80%) of the total mass of nscs in our model. both nsc growth through in situ star formation and that through star cluster migration are found to generate nsc—host galaxy scaling correlations that are shallower than the same correlations for mbhs. we explore the role of galaxy mergers on the evolution of nscs and show that observational data on nsc—host galaxy scaling relations provide evidence of partial erosion of nscs by mbh binaries in luminous galaxies. we show that this observational feature is reproduced by our models, and we make predictions about the nsc and mbh occupation fraction in galaxies. we conclude by discussing several implications for theories of nsc formation. | the coevolution of nuclear star clusters, massive black holes, and their host galaxies |
winds accelerated by active galactic nuclei (agns) are invoked in the most successful models of galaxy evolution to explain the observed physical and evolutionary properties of massive galaxies. winds are expected to deposit energy and momentum into the interstellar medium (ism), thus regulating both star formation and supermassive black hole (smbh) growth. we undertook a multiband observing program aimed at obtaining a complete census of winds in a sample of wise/sdss selected hyper-luminous (wissh) quasars (qsos) at z ≈ 2-4. we analyzed the rest-frame optical (i.e. lbt/luci and vlt/sinfoni) and uv (i.e. sdss) spectra of 18 randomly selected wissh qsos to measure the smbh mass and study the properties of winds both in the narrow line region (nlr) and broad line region (blr) traced by blueshifted or skewed [oiii] and civ emission lines, respectively. these wissh qsos are powered by smbh with masses ≳109 m⊙ accreting at 0.4 < λedd < 3.1. we found the existence of two subpopulations of hyper-luminous qsos characterized by the presence of outflows at different distances from the smbh. one population (i.e. [oiii] sources) exhibits powerful [oiii] outflows, a rest-frame equivalent width (rew) of the civ emission rewciv ≈ 20-40 å, and modest civ velocity shift (vcivpeak) with respect to the systemic redshift (vcivpeak < 2000 km s-1). the second population (i.e. weak [oiii] sources), representing 70% of the analyzed wissh qsos, shows weak or absent [oiii] emission and an extremely large blueshifted civ emission (vcivpeak up to 8000 km s-1 and rewciv < 20 å). we propose two explanations for the observed behavior of the strength of the [oiii] emission in terms of the orientation effects of the line of sight and ionization cone. the dichotomy in the presence of blr and nlr winds could be likely due to inclination effects considering a polar geometry scenario for the blr winds. in a few cases these winds are remarkably as powerful as those revealed in the nlr in the [oiii] qsos (ėkin 1044-45 erg s-1). we also investigated the dependence of these civ winds on fundamental agn parameters such as bolometric luminosity (lbol), eddington ratio (λedd), and uv-to-x-ray continuum slope (αox). we found a strong correlation with lbol and an anti-correlation with αox whereby the higher the luminosity, the steeper the ionizing continuum described by means of αox and the larger the blueshift of the civ emission line. finally, the observed dependence vcivpeak ∝ lbol0.28 ± 0.04 is consistent with a radiatively-driven-winds scenario, where a strong uv continuum is necessary to launch the wind and a weakness of the x-rayemission is fundamental to prevent overionization of the wind itself. | the wissh quasars project. iv. broad line region versus kiloparsec-scale winds |
particles may be accelerated in magnetized coronae via magnetic reconnections and/or plasma turbulence, leading to high-energy neutrinos and soft γ-rays. we evaluate the detectability of neutrinos from nearby bright seyfert galaxies identified by x-ray measurements. in the disk-corona model, we find that ngc 1068 is the most promising seyfert galaxy in the northern sky, where icecube is the most sensitive, and show prospects for the identification of aggregated neutrino signals from seyfert galaxies bright in x-rays. moreover, we demonstrate that nearby seyfert galaxies are promising targets for the next generation of neutrino telescopes such as km3net and icecube-gen2. for km3net, cen a can be the most promising source in the southern sky if a significant fraction of the observed x-rays come from the corona, and it could be identified in few years of km3net operation. our results reinforce the idea that hidden cores of supermassive black holes are the dominant sources of the high-energy neutrino emission and underlines the necessity of better sensitivity to medium-energy ranges in future neutrino detectors for identifying the origin of high-energy cosmic neutrinos. | high-energy neutrinos from magnetized coronae of active galactic nuclei and prospects for identification of seyfert galaxies and quasars in neutrino telescopes |
we address the effect of orientation of the accretion disk plane and the geometry of the broad-line region (blr) as part of an effort to understand the distribution of quasars in optical plane of the quasar main sequence. we utilize the photoionization code cloudy to model the blr incorporating the grossly underestimated form factor (f). treating the aspect of viewing angle appropriately, we confirm the dependence of the r fe iisequence on l/{l}edd} and on the related observational trends—as a function of the sed shape, cloud density, and composition, verified from prior observations. sources with r fe iiin the range 1-2 (about 10% of all quasars, the so-called extreme population a [xa] quasars) are explained as sources of high, and possibly extreme eddington ratio along the r fe iisequence. this result has important implications for the exploitation of xa sources as distance indicators for cosmology. fe ii emitters with r fe ii> 2 are very rare (<1% of all type 1 quasars). our approach also explains the rarity of these highest fe ii emitters as extreme xa sources, and constrains the viewing angle ranges with increasing hβ fwhm. | the quasar main sequence explained by the combination of eddington ratio, metallicity, and orientation |
high cadence, high quality observations of active galactic nuclei (agn) clearly show continuum variations with lags, relative to the shortest observed variable uv continuum that increase with wavelength ('lag spectra'). these have been attributed to the irradiation and heating of the central accretion disc by the central x-ray emitting corona. an alternative explanation, connecting the observed lag-spectra to line and continuum emission from gas in the broad line region (blr), has also been proposed. in this paper i show the clear spectral signature of the time-dependent diffuse gas emission in the lag-spectrum of 6 agn. i also show a new lag-luminosity relationship for 9 objects which is a scaled down version of the well known τ(hβ)-l5100 relationship in agn. the shape of the lag-spectrum, and its normalization, are entirely consistent with diffuse emission from radiation pressure supported clouds in a blr with a covering factor of about 0.2. while some contributions to the continuum lag from the irradiated disc cannot be excluded, there is no need for this explanation. | continuum reverberation mapping and a new lag-luminosity relationship for agn |
feedback from accreting supermassive black holes (smbhs) is thought to be a primary driver of quenching in massive galaxies, but how to best implement smbh physics into galaxy formation simulations remains ambiguous. as part of the feedback in realistic environments (fire) project, we explore the effects of different modelling choices for smbh accretion and feedback in a suite of ~500 cosmological zoom-in simulations across a wide range of halo mass (1010-1013 m⊙). within the suite, we vary the numerical schemes for bh accretion and feedback, accretion efficiency, and the strength of mechanical, radiative, and cosmic ray feedback independently. we then compare the outcomes to observed galaxy scaling relations. we find several models satisfying observational constraints for which the energetics in different feedback channels are physically plausible. interestingly, cosmic rays accelerated by smbhs play an important role in many plausible models. however, it is non-trivial to reproduce scaling relations across halo mass, and many model variations produce qualitatively incorrect results regardless of parameter choices. the growth of stellar and bh mass are closely related: for example, overmassive bhs tend to overquench galaxies. bh mass is most strongly affected by the choice of accretion efficiency in high-mass haloes, but by feedback efficiency in low-mass haloes. the amount of star formation suppression by smbh feedback in low-mass haloes is determined primarily by the time-integrated feedback energy. for massive galaxies, the 'responsiveness' of a model (how quickly and powerfully the bh responds to gas available for accretion) is an additional important factor for quenching. | exploring supermassive black hole physics and galaxy quenching across halo mass in fire cosmological zoom simulations |
in tombesi et al., we reported the first direct evidence for a quasar accretion disk wind driving a massive (>100 m ⊙ yr-1) molecular outflow. the target was f11119+3257, an ultraluminous infrared galaxy (ulirg) with unambiguous type 1 quasar optical broad emission lines. the energetics of the accretion disk wind and molecular outflow were found to be consistent with the predictions of quasar feedback models where the molecular outflow is driven by a hot energy-conserving bubble inflated by the inner quasar accretion disk wind. however, this conclusion was uncertain because the mass outflow rate, momentum flux, and mechanical power of the outflowing molecular gas were estimated from the optically thick oh 119 μm transition profile observed with herschel. here, we independently confirm the presence of the molecular outflow in f11119+3257, based on the detection of ∼±1000 km s-1 blue- and redshifted wings in the co(1-0) emission line profile derived from deep alma observations obtained in the compact array configuration (∼2.″8 resolution). the broad co(1-0) line emission appears to be spatially extended on a scale of at least ∼7 kpc from the center. mass outflow rate, momentum flux, and mechanical power of (80-200) {r}7-1 m ⊙ yr-1, (1.5-3.0) {r}7-1 l agn/c, and (0.15-0.40)% {r}7-1 {l}{agn}, respectively, are inferred from these data, assuming a co-to-h2 conversion factor appropriate for a ulirg (r 7 is the radius of the outflow normalized to 7 kpc, and l agn is the agn luminosity). these rates are time-averaged over a flow timescale of 7 × 106 yr. they are similar to the oh-based rates time-averaged over a flow timescale of 4 × 105 yr, but about a factor of 4 smaller than the local (“instantaneous” ≲105 yr) oh-based estimates cited in tombesi et al. the implications of these new results are discussed in the context of time-variable quasar-mode feedback and galaxy evolution. the need for an energy-conserving bubble to explain the molecular outflow is also reexamined. | quasar feedback in the ultraluminous infrared galaxy f11119+3257: connecting the accretion disk wind with the large-scale molecular outflow |
we present the first results of an atacama large millimeter array survey of the lower fine-structure line of atomic carbon [c i] {(}3{p}1 {--}{}3{p}0) in far-infrared-selected galaxies on the main sequence at z ∼ 1.2 in the cosmos field. we compare our sample with a comprehensive compilation of data available in the literature for local and high-redshift starbursting systems and quasars. we show that the [c i] (3 p 1 → 3 p 0) luminosity correlates on global scales with the infrared luminosity {l}ir}, similar to low-j co transitions. we report a systematic variation of {l}{[{{c}{{i}}]}3{p}1 {--}{}3{p}0}{\prime }/{l}ir} as a function of the galaxy type, with the ratio being larger for main-sequence galaxies than for starbursts and submillimeter galaxies at fixed {l}ir}. the {l}{[{{c}{{i}}]}3{p}1 {--}{}3{p}0}{\prime }/{l}co(2-1)}{\prime } and {m}[{{c}{{i}}]}/{m}dust} mass ratios are similar for main-sequence galaxies and for local and high-redshift starbursts within a 0.2 dex intrinsic scatter, suggesting that [c i] is a good tracer of molecular gas mass as co and dust. we derive a fraction of {f}[{{c}{{i}}]}={m}[{{c}{{i}}]}/{m}{{c}}∼ 3 % {--}13 % of the total carbon mass in the atomic neutral phase. moreover, we estimate the neutral atomic carbon abundance, the fundamental ingredient to calibrate [c i] as a gas tracer, by comparing {l}{[{{c}{{i}}]}3{p}1 {--}{}3{p}0}{\prime } and available gas masses from co lines and dust emission. we find lower [c i] abundances in main-sequence galaxies than in starbursting systems and submillimeter galaxies as a consequence of the canonical α co and gas-to-dust conversion factors. this argues against the application to different galaxy populations of a universal standard [c i] abundance derived from highly biased samples. | a survey of atomic carbon [c i] in high-redshift main-sequence galaxies |
we report the discovery of six active galactic nuclei (agns) caught “turning on” during the first nine months of the zwicky transient facility (ztf) survey. the host galaxies were classified as low-ionization nuclear emission-line region galaxies (liners) by weak narrow forbidden line emission in their archival sdss spectra, and detected by ztf as nuclear transients. in five of the cases, we found via follow-up spectroscopy that they had transformed into broad-line agns, reminiscent of the changing-look liner iptf16bco. in one case, ztf18aajupnt/at2018dyk, follow-up hubble space telescope ultraviolet and ground-based optical spectra revealed the transformation into a narrow-line seyfert 1 with strong [fe vii, x, xiv] and he ii λ 4686 coronal lines. swift monitoring observations of this source reveal bright uv emission that tracks the optical flare, accompanied by a luminous soft x-ray flare that peaks ∼60 days later. spitzer follow-up observations also detect a luminous mid-infrared flare, implying a large covering fraction of dust. archival light curves of the entire sample from crts, atlas, and asas-sn constrain the onset of the optical nuclear flaring from a prolonged quiescent state. here we present the systematic selection and follow-up of this new class of changing-look liners, compare their properties to previously reported changing-look seyfert galaxies, and conclude that they are a unique class of transients well-suited to test the uncertain physical processes associated with the liner accretion state. | a new class of changing-look liners |
dual supermassive black holes (smbhs) at ~kiloparsec scales are the progenitor population of smbh mergers and play an important role in understanding the pairing and dynamical evolution of massive black holes in galaxy mergers. because of the stringent resolution requirement and the apparent rareness of these small-separation pairs, there are scarce observational constraints on this population, with few confirmed dual smbhs at <10 kpc separations at z > 1. here we present results from a pilot search for kiloparsec-scale dual quasars selected with gaia data release 2 (dr2) astrometry and followed up with hubble space telescope (hst) wide field camera 3 dual-band (f475w and f814w) snapshot imaging. our targets are quasars primarily selected with the varstrometry technique, i.e., light centroid jitter caused by asynchronous variability from both members in an unresolved quasar pair, supplemented by subarcsecond pairs already resolved by gaia dr2. we find an overall high fraction of hst-resolved pairs among the varstrometry-selected quasars (unresolved in gaia dr2), ~30%-50%, increasing toward high redshift (~60%-80% at z > 1.5). we discuss the nature of the 45 resolved subarcsecond pairs based on hst and supplementary data. a substantial fraction (~40%) of these pairs are likely physical quasar pairs or gravitationally lensed quasars. we also discover a triple quasar candidate and a quadruply lensed quasar, which is among the smallest-separation quadruple lenses. these results provide important guidelines to improve varstrometry selection and follow-up confirmation of ~kiloparsec-scale dual smbhs at high redshift. | varstrometry for off-nucleus and dual subkiloparsec agn (vodka): hubble space telescope discovers double quasars |
in this paper, we provide predictions for the black hole (bh) population that would be observable with planned jwst surveys at 5 ≤ z ≤ 15. we base our study on the recently developed cosmic archaeology tool, which allows us to model bh seeds formation and growth while being consistent with the general population of active galactic nuclei (agns) and galaxies observed at 4 ≤ z ≤ 7. we find that jwst planned surveys will provide a complementary view on active bhs at z > 5, with jades-medium/-deep being capable of detecting the numerous bhs that populate the faint-end of the distribution, cosmos-web sampling a large enough area to detect the rarest brightest systems, and ceers/primer bridging the gap between these two regimes. the relatively small field of view of the above surveys preferentially selects bhs with masses 6 ≤ log(mbh/m⊙) < 8 at 7 ≤ z < 10, residing in relatively metal poor (log(z/z⊙) ≥ -2) and massive (8 ≤ log(m*/m⊙) < 10) galaxies. at z ≥ 10, only jades-deep will have the sensitivity to detect growing bhs with masses 4 ≤ log(mbh/m⊙) < 6, hosted by more metal poor (-3 ≤ log(z/z⊙) < -2) and less massive (6 ≤ log(m*/m⊙) < 8) galaxies. in our model, the latter population corresponds to heavy bh seeds formed by the direct collapse of supermassive stars in their earliest phases of mass growth. detecting these systems would provide invaluable insights on the nature and early growth of the first bh seeds. | seeking the growth of the first black hole seeds with jwst |
we present the analysis of the full shape of anisotropic clustering measurement from the extended baryon oscillation spectroscopic survey (eboss) quasar sample together with the combined galaxy sample from the baryon oscillation spectroscopic survey (boss), re-analysed using an updated recipe for the non-linear matter power spectrum and the non-local bias parameters. we obtain constraints for flat lambda cold dark matter cosmologies, focusing on the cosmological parameters that are independent of the hubble parameter h. our recovered value for the root mean square (rms) linear perturbation theory variance as measured on the scale of $12\, {\rm mpc}$ is σ12 = 0.805 ± 0.049, while using the traditional reference scale of $8\, h^{-1}\, {\rm mpc}$ gives σ8 = 0.815 ± 0.044. we quantify the agreement between our measurements and the latest cosmic microwave background data from planck using the suspiciousness metric, and find them to be consistent within 0.64 ± 0.03σ. combining our clustering constraints with the 3 × 2pt data sample from the dark energy survey year 1 release slightly degrades this agreement to the level of 1.54 ± 0.08σ, while still showing an overall consistency with planck. we furthermore study the effect of imposing a planck - like prior on the parameters that define the shape of the linear matter power spectrum, and find significantly tighter constraints on the parameters that control the evolution of density fluctuations. in particular, the combination of low-redshift data sets prefers a value of the physical dark energy density ωde = 0.335 ± 0.011, which is 1.7σ higher than the one preferred by planck. | cosmological implications of the full shape of anisotropic clustering measurements in boss and eboss |
measurements of time-delay cosmography of lensed quasars can provide an independent probe to explore the expansion history of the late-time universe. in this paper, we employ the time-delay cosmography measurements from seven lenses (here abbreviated as the td data) to constrain interacting dark energy (ide) models. we mainly focus on the scenario of vacuum energy (with w = -1) interacting with cold dark matter, and consider four typical cases of the interaction form q. when the td data alone are employed, we find that the ide models with q ∝ ρde seem to have an advantage in relieving the h0 tension between the cosmic microwave background (cmb) and td data. when the td data are added to the cmb+bao+sn+h0 data, we find that (i) the coupling parameter β in all the considered ide models is positive within 1σ range, implying a mild preference for the case of cold dark matter decaying into dark energy; (ii) the ide model with q = βh0ρc slightly relieves the s8 tension, but the other considered ide models further aggravate this tension; (iii) the akaike information criteria of the ide models with q ∝ ρc are lower than that of the λcdm model, indicating that these ide models are more preferred by the current mainstream data. we conclude that the considered ide models have their own different advantages when the td data are employed, and none of them can achieve good scores in all aspects. | constraints on interacting dark energy models from time-delay cosmography with seven lensed quasars |
pulsar timing arrays (ptas) around the world are using the incredible consistency of millisecond pulsars to measure low-frequency gravitational waves from (super)massive black hole (mbh) binaries. we use comprehensive mbh merger models based on cosmological hydrodynamic simulations to predict the spectrum of the stochastic gravitational wave background (gwb). we use real time-of-arrival specifications from the european, nanograv, parkes, and international pta (ipta) to calculate realistic times to detection of the gwb across a wide range of model parameters. in addition to exploring the parameter space of environmental hardening processes (in particular: stellar scattering efficiencies), we have expanded our models to include eccentric binary evolution which can have a strong effect on the gwb spectrum. our models show that strong stellar scattering and high characteristic eccentricities enhance the gwb strain amplitude near the pta-sensitive `sweet-spot' (near the frequency f = 1 yr-1), slightly improving detection prospects in these cases. while the gwb amplitude is degenerate between cosmological and environmental parameters, the location of a spectral turnover at low frequencies (f ≲ 0.1 yr-1) is strongly indicative of environmental coupling. at high frequencies (f ≳ 1 yr-1), the gwb spectral index can be used to infer the number density of sources and possibly their eccentricity distribution. even with merger models that use pessimistic environmental and eccentricity parameters, if the current rate of pta expansion continues, we find that the ipta is highly likely to make a detection within about 10 yr. | the gravitational wave background from massive black hole binaries in illustris: spectral features and time to detection with pulsar timing arrays |
context. a tight non-linear relation exists between the x-ray and uv emission in quasars (i.e. lx ∝luvγ), with a dispersion of 0.2 dex over approximately three orders of magnitude in luminosity. such observational evidence has two relevant consequences: (1) an ubiquitous physical mechanism must regulate the energy transfer from the accretion disc to the x-ray emitting corona; and (2) the non-linearity of the relation provides a new, powerful way to estimate the absolute luminosity, turning quasars into a new class of standard candles.aims: here we propose a modified version of this relation, which involves the emission line full-width half maximum, lx ∝luvγ̂υβ̂fwhm.methods: we interpret this new relation through a simple, ad hoc model of accretion disc corona, derived from previous works in the literature where it is assumed that reconnection and magnetic loops above the accretion disc can account for the production of the primary x-ray radiation.results: we find that the monochromatic optical-uv (2500 å) and x-ray (2 kev) luminosities depend on the black hole mass and accretion rate as luv ∝ mbh4/3(ṁ/ṁedd)2/3 and lx ∝ mbh19/21(ṁ/ṁedd)5/21, respectively. assuming a broad line region size function of the disc luminosity rblr ∝ ldisc0.5 we finally have that lx ∝ luv4/7υ4/7fwhm. such relation is remarkably consistent with the slopes and the normalisation obtained from a fit of a sample of 545 optically selected quasars from sdss dr7 cross matched with the latest xmm-newton catalogue 3xmm-dr6.conclusions: the homogeneous sample used here has a dispersion of 0.21 dex, which is much lower than previous works in the literature and suggests a tight physical relation between the accretion disc and the x-ray emitting corona. we also obtained a possible physical interpretation of the lx-luv relation (considering also the effect of υfwhm), which puts the determination of distances based on this relation on a sounder physical grounds. the proposed new relation does not evolve with time, and thus it can be employed as a cosmological indicator to robustly estimate cosmological parameters. | quasars as standard candles. i. the physical relation between disc and coronal emission |
we present spectroscopic identification of 32 new quasars and luminous galaxies discovered at 5.7 < z ≤ 6.8. this is the second in a series of papers presenting the results of the subaru high-z exploration of low-luminosity quasars (shellqs) project, which exploits the deep multi-band imaging data produced by the hyper suprime-cam (hsc) subaru strategic program survey. the photometric candidates were selected by a bayesian probabilistic algorithm, and then observed with spectrographs on the gran telescopio canarias and the subaru telescope. combined with the sample presented in the previous paper of this series, we have now identified 64 hsc sources over about 430 deg2, which include 33 high-z quasars, 14 high-z luminous galaxies, two [o iii] emitters at z ∼ 0.8, and 15 galactic brown dwarfs. the new quasars have considerably lower luminosity (m1450 ∼ -25 to -22 mag) than most of the previously known high-z quasars. several of these quasars have luminous (>1043 erg s-1) and narrow (< 500 km s-1) lyα lines, and also a possible mini broad-absorption-line system of n v λ1240 in the composite spectrum, which clearly separate them from typical quasars. on the other hand, the high-z galaxies have extremely high luminosities (m1450 ∼ -24 to -22 mag) compared to other galaxies found at similar redshifts. with the discovery of these new classes of objects, we are opening up new parameter spaces in the high-z universe. further survey observations and follow-up studies of the identified objects, including the construction of the quasar luminosity function at z ∼ 6, are ongoing. | subaru high-z exploration of low-luminosity quasars (shellqs). ii. discovery of 32 quasars and luminous galaxies at 5.7 < z ≤ 6.8 |
the discovery of quasars a few hundred megayears after the big bang represents a major challenge to our understanding of black holes as well as galaxy formation and evolution. quasars' luminosity is produced by extreme gas accretion onto black holes, which have already reached masses of m bh > 109 m ⊙ by z ∼ 6. simultaneously, their host galaxies form hundreds of stars per year, using up gas in the process. to understand which environments are able to sustain the rapid formation of these extreme sources, we started a very large telescope/multi-unit spectroscopic explorer (muse) effort aimed at characterizing the surroundings of a sample of 5.7 < z < 6.6 quasars, which we have dubbed the reionization epoch quasar investigation with muse (requiem) survey. we here present results of our searches for extended lyα halos around the first 31 targets observed as part of this program. reaching 5σ surface brightness limits of 0.1-1.1 × 10-17 erg s-1 cm-2 arcsec-2 over a 1 arcsec2 aperture, we were able to unveil the presence of 12 lyα nebulae, eight of which are newly discovered. the detected nebulae show a variety of emission properties and morphologies with luminosities ranging from 8 × 1042 to 2 × 1044 erg s-1, fwhms between 300 and 1700 km s-1, sizes <30 pkpc, and redshifts consistent with those of the quasar host galaxies. as the first statistical and homogeneous investigation of the circumgalactic medium of massive galaxies at the end of the reionization epoch, the requiem survey enables the study of the evolution of the cool gas surrounding quasars in the first 3 gyr of the universe. a comparison with the extended lyα emission observed around bright ({m}1450 ≲ -25 mag) quasars at intermediate redshift indicates little variations on the properties of the cool gas from z ∼ 6 to z ∼ 3, followed by a decline in the average surface brightness down to z ∼ 2. | the requiem survey. i. a search for extended lyα nebular emission around 31 z > 5.7 quasars |
the observed massive end of the galaxy stellar mass function is steeper than its predicted dark matter halo counterpart in the standard λ cold dark matter paradigm. in this paper, we investigate the impact of active galactic nuclei (agn) feedback on star formation in massive galaxies. we isolate the impact of agn by comparing two simulations from the horizon suite, which are identical except that one also includes supermassive black holes (smbhs) and related feedback models. this allows us to cross-identify individual galaxies between simulations and quantify the effect of agn feedback on their properties, including stellar mass and gas outflows. we find that massive galaxies (m* ≥ 1011 m⊙) are quenched by agn feedback to the extent that their stellar masses decrease by up to 80 per cent at z = 0. smbhs affect their host halo through a combination of outflows that reduce their baryonic mass, particularly for galaxies in the mass range 109 m⊙ ≤ m* ≤ 1011 m⊙, and a disruption of central gas inflows, which limits in situ star formation. as a result, net gas inflows on to massive galaxies, m* ≥ 1011 m⊙, drop by up to 70 per cent. we measure a redshift evolution in the stellar mass ratio of twin galaxies with and without agn feedback, with galaxies of a given stellar mass showing stronger signs of quenching earlier on. this evolution is driven by a progressive flattening of the msmbh-m* relation with redshift, particularly for galaxies with m* ≤ 1010 m⊙. msmbh/m* ratios decrease over time, as falling average gas densities in galaxies curb smbh growth. | cosmic evolution of stellar quenching by agn feedback: clues from the horizon-agn simulation |
we have performed a search over 3440 deg2 of epoch 1 (2017-2019) of the very large array sky survey to identify unobscured quasars in the optical (0.2 < z < 3.2) and obscured active galactic nuclei (agns) in the infrared that have brightened dramatically in the radio over the past one to two decades. these sources would have been previously classified as "radio-quiet" quasars based on upper limits from the faint images of the radio sky at twenty cm survey (1993-2011), but they are now consistent with "radio-loud" quasars ( ${l}_{3\mathrm{ghz}}={10}^{40\mbox{--}42}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ ). a quasi-simultaneous, multiband (∼1-18 ghz) follow-up study of 14 sources with the vla has revealed compact sources (<0"1 or <1 kpc) with peaked radio spectral shapes. the high-amplitude variability over decadal timescales at 1.5 ghz (100% to >2500%) but roughly steady fluxes over a few months at 3 ghz are inconsistent with extrinsic variability due to propagation effects, thus favoring an intrinsic origin. we conclude that our sources are powerful quasars hosting compact/young jets. this challenges the generally accepted idea that "radio-loudness" is a property of the quasar/agn population that remains fixed on human timescales. our study suggests that frequent episodes of short-lived agn jets that do not necessarily grow to large scales may be common at high redshift. we speculate that intermittent but powerful jets on subgalactic scales could interact with the interstellar medium, possibly driving feedback capable of influencing galaxy evolution. | quasars that have transitioned from radio-quiet to radio-loud on decadal timescales revealed by vlass and first |
growing supermassive black holes (∼ {10}9 {m}⊙ ) that power luminous z> 6 quasars from light seeds—the remnants of the first stars—within a gyr of the big bang poses a timing challenge. the formation of massive black hole seeds via direct collapse with initial masses ∼ {10}4{--}{10}5 {m}⊙alleviates this problem. viable direct-collapse black hole formation sites, the satellite halos of star-forming galaxies, merge and acquire stars to produce a new, transient class of high-redshift objects, obese black hole galaxies (obgs). the accretion luminosity outshines that of the stars in obgs. we predict the multi-wavelength energy output of obgs and growing pop iii remnants at z = 9 for standard and slim disk accretion, as well as high and low metallicities of the associated stellar population. we derive robust selection criteria for obgs—a pre-selection to eliminate blue sources, followed by color-color cuts ([{f}090w-{f}220w]> 0;-0.3< [{f}200w-{f}444w]< 0.3) and the ratio of x-ray flux to rest-frame optical flux ({f}x/{f}444w\gg 1). our cuts sift out obgs from other bright, high- and low-redshift contaminants in the infrared. obgs with predicted {m}{ab}< 25 are unambiguously detectable by the mid-infrared instrument (miri), on the upcoming james webb space telescope (jwst). for parameters explored here, growing pop iii remnants with predicted {m}{ab}< 30 will likely be undetectable by jwst. we demonstrate that jwst has the power to discriminate between initial seeding mechanisms. | unveiling the first black holes with jwst:multi-wavelength spectral predictions |
we present a new catalog of narrow-line seyfert 1 (nlsy1) galaxies from the sloan digital sky survey data release 12 (sdss dr12). this was obtained by a systematic analysis through modeling of the continuum and emission lines of the spectra of all the 68,859 sdss dr12 objects that are classified as “qso” by the sdss spectroscopic pipeline with z< 0.8 and a median signal-to-noise ratio (s/n) > 2 pixel-1. this catalog contains a total of 11,101 objects, which is about 5 times larger than the previously known nlsy1 galaxies. their monochromatic continuum luminosity at 5100 å is found to be strongly correlated with hβ, hα, and [o iii] emission line luminosities. the optical fe ii strength in nlsy1 galaxies is about two times larger than the broad-line seyfert 1 (blsy1) galaxies. about 5% of the catalog sources are detected in the first survey. the eddington ratio ({ξ }{edd}) of nlsy1 galaxies has an average of {log} {ξ }{edd} of -0.34, much higher than -1.03 found for blsy1 galaxies. their black hole masses ({m}{bh}) have an average of {log} {m}{bh} of 6.9 {m}⊙ , which is less than blsy1 galaxies, which have an average of {log} {m}{bh} of 8.0 {m}⊙ . the {m}{bh} of nlsy1 galaxies is found to be correlated with their host galaxy velocity dispersion. our analysis suggests that geometrical effects playing an important role in defining nlsy1 galaxies and their {m}{bh} deficit is perhaps due to their lower inclination compared to blsy1 galaxies. | a catalog of narrow line seyfert 1 galaxies from the sloan digital sky survey data release 12 |
gravitational time delays provide a powerful one-step measurement of h0, independent of all other probes. one key ingredient in time-delay cosmography are high-accuracy lens models. those are currently expensive to obtain, both, in terms of computing and investigator time (105-106 cpu hours and ~0.5-1 yr, respectively). major improvements in modelling speed are therefore necessary to exploit the large number of lenses that are forecast to be discovered over the current decade. in order to bypass this roadblock, we develop an automated modelling pipeline and apply it to a sample of 31 lens systems, observed by the hubble space telescope in multiple bands. our automated pipeline can derive models for 30/31 lenses with few hours of human time and <100 cpu hours of computing time for a typical system. for each lens, we provide measurements of key parameters and predictions of magnification as well as time delays for the multiple images. we characterize the cosmography-readiness of our models using the stability of differences in the fermat potential (proportional to time delay) with respect to modelling choices. we find that for 10/30 lenses, our models are cosmography or nearly cosmography grade (<3 per cent and 3-5 per cent variations). for 6/30 lenses, the models are close to cosmography grade (5-10 per cent). these results utilize informative priors and will need to be confirmed by further analysis. however, they are also likely to improve by extending the pipeline modelling sequence and options. in conclusion, we show that uniform cosmography grade modelling of large strong lens samples is within reach. | strides: automated uniform models for 30 quadruply imaged quasars |
we present the stacking analysis of a sample of 48 quasi-stellar objects (qsos) at 4.5 < z < 7.1 detected by the atacama large millimetre array (alma) in the [cii] λ158 μm emission line to investigate the presence and the properties of massive, cold outflows associated with broad wings in the [cii] profile. the high sensitivity reached through this analysis allows us to reveal very broad [cii] wings tracing the presence of outflows with velocities in excess of 1000 km s-1. we find that the luminosity of the broad [cii] emission increases with lagn, while it does not significantly depend on the star formation rate of the host galaxy, indicating that the central active galactic nucleus (agn) is the main driving mechanism of the [cii] outflows in these powerful, distant qsos. from the stack of the alma cubes, we derive an average outflow spatial extent of ∼3.5 kpc. the average atomic neutral mass outflow rate inferred from the stack of the whole sample is ṁout ∼ 100 m⊙ yr-1, while for the most luminous systems it increases to ∼200 m⊙ yr-1. the associated outflow kinetic power is about 0.1% of lagn, while the outflow momentum rate is ∼lagn/c or lower, suggesting that these outflows are either driven by radiation pressure onto dusty clouds or, alternatively, are driven by the nuclear wind and energy conserving but with low coupling with the interstellar medium. we discuss the implications of the resulting feedback effect on galaxy evolution in the early universe. the reduced continuum subtracted datacubes are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/630/a59 | widespread qso-driven outflows in the early universe |
we report the discovery of a new `changing-look' quasar, sdss j101152.98+544206.4, through repeat spectroscopy from the time domain spectroscopic survey. this is an addition to a small but growing set of quasars whose blue continua and broad optical emission lines have been observed to decline by a large factor on a time-scale of approximately a decade. the 5100 å monochromatic continuum luminosity of this quasar drops by a factor of >9.8 in a rest-frame time interval of <9.7 yr, while the broad hα luminosity drops by a factor of 55 in the same amount of time. the width of the broad hα line increases in the dim state such that the black hole mass derived from the appropriate single-epoch scaling relation agrees between the two epochs within a factor of 3. the fluxes of the narrow emission lines do not appear to change between epochs. the light curve obtained by the catalina sky survey suggests that the transition occurs within a rest-frame time interval of approximately 500 d. we examine three possible mechanisms for this transition suggested in the recent literature. an abrupt change in the reddening towards the central engine is disfavoured by the substantial difference between the time-scale to obscure the central engine and the observed time-scale of the transition. a decaying tidal disruption flare is consistent with the decay rate of the light curve but not with the prolonged bright state preceding the decay; nor can this scenario provide the power required by the luminosities of the emission lines. an abrupt drop in the accretion rate on to the supermassive black hole appears to be the most plausible explanation for the rapid dimming. | now you see it, now you don't: the disappearing central engine of the quasar j1011+5442 |
changing-look quasars are a recently identified class of active galaxies in which the strong uv continuum and/or broad optical hydrogen emission lines associated with unobscured quasars either appear or disappear on time-scales of months to years. the physical processes responsible for this behaviour are still debated, but changes in the black hole accretion rate or accretion disc structure appear more likely than changes in obscuration. here, we report on four epochs of spectroscopy of sdss j110057.70-005304.5, a quasar at a redshift of z = 0.378 whose uv continuum and broad hydrogen emission lines have faded, and then returned over the past ≈20 yr. the change in this quasar was initially identified in the infrared, and an archival spectrum from 2010 shows an intermediate phase of the transition during which the flux below rest frame ≈3400 å has decreased by close to an order of magnitude. this combination is unique compared to previously published examples of changing-look quasars, and is best explained by dramatic changes in the innermost regions of the accretion disc. the optical continuum has been rising since mid-2016, leading to a prediction of a rise in hydrogen emission-line flux in the next year. increases in the infrared flux are beginning to follow, delayed by a ∼3 yr observed time-scale. if our model is confirmed, the physics of changing-look quasars are governed by processes at the innermost stable circular orbit around the black hole, and the structure of the innermost disc. the easily identifiable and monitored changing-look quasars would then provide a new probe and laboratory of the nuclear central engine. | a new physical interpretation of optical and infrared variability in quasars |
to constrain the nature and fraction of the ionized gas outflows in active galactic nuclei (agns), we perform a detailed analysis on gas kinematics as manifested by the velocity dispersion and shift of the [{{o}}\{{iii}}] λ5007 emission line, using a large sample of ∼39,000 type 2 agns at z < 0.3. first, we confirm a broad correlation between [{{o}} {{iii}}] and stellar velocity dispersions, indicating that the bulge gravitational potential plays a main role in determining the [{{o}} {{iii}}] kinematics. however, [{{o}} {{iii}}] velocity dispersion is on average larger than stellar velocity dispersion by a factor of 1.3-1.4 for agns with double gaussian [{{o}} {{iii}}], suggesting that the non-gravitational component, i.e., outflows, is almost comparable to the gravitational component. second, the increase of the [{{o}} {{iii}}] velocity dispersion (after normalized by stellar velocity dispersion) with both agn luminosity and eddington ratio suggests that non-gravitational kinematics are clearly linked to agn accretion. the distribution in the [{{o}} {{iii}}] velocity-velocity dispersion diagram dramatically expands toward large values with increasing agn luminosity, implying that the launching velocity of gas outflows increases with agn luminosity. third, the majority of luminous agns present the non-gravitational kinematics in the [{{o}} {{iii}}] profile. these results suggest that ionized gas outflows are prevalent among type 2 agns. on the other hand, we find no strong trend of the [{{o}} {{iii}}] kinematics with radio luminosity, once we remove the effect of the bulge gravitational potential, indicating that ionized gas outflows are not directly related to radio activity for the majority of type 2 agns. | the prevalence of gas outflows in type 2 agns |
we present all-sky modelling of the high resolution planck, iras, and wise infrared (ir) observations using the physical dust model presented by draine & li in 2007 (dl, apj, 657, 810). we study the performance and results of this model, and discuss implications for future dust modelling. the present work extends the dl dust modelling carried out on nearby galaxies using herschel and spitzer data to galactic dust emission. we employ the dl dust model to generate maps of the dust mass surface density σmd, the dust optical extinction av, and the starlight intensity heating the bulk of the dust, parametrized by umin. the dl model reproduces the observed spectral energy distribution (sed) satisfactorily over most of the sky, with small deviations in the inner galactic disk and in low ecliptic latitude areas, presumably due to zodiacal light contamination. in the andromeda galaxy (m31), the present dust mass estimates agree remarkably well (within 10%) with dl estimates based on independent spitzer and herschel data. we compare the dl optical extinction av for the diffuse interstellar medium (ism) with optical estimates for approximately 2 × 105 quasi-stellar objects (qsos) observed inthe sloan digital sky survey (sdss). the dl av estimates are larger than those determined towards qsos by a factor of about 2, which depends on umin. the dl fitting parameter umin, effectively determined by the wavelength where the sed peaks, appears to trace variations in the far-ir opacity of the dust grains per unit av, and not only in the starlight intensity. these results show that some of the physical assumptions of the dl model will need to be revised. to circumvent the model deficiency, we propose an empirical renormalization of the dl av estimate, dependent of umin, which compensates for the systematic differences found with qso observations. this renormalization, made to match the av estimates towards qsos, also brings into agreement the dl av estimates with those derived for molecular clouds from the near-ir colours of stars in the 2 micron all sky survey (2mass). the dl model and the qsos data are also used to compress the spectral information in the planck and iras observations for the diffuse ism to a family of 20 seds normalized per av, parameterized by umin, which may be used to test and empirically calibrate dust models. the family of seds and the maps generated with the dl model are made public in the planck legacy archive. | planck intermediate results. xxix. all-sky dust modelling with planck, iras, and wise observations |
enormous lyα nebulae (elane), unique tracers of galaxy density peaks, are predicted to lie at the nodes and intersections of cosmic filamentary structures. previous successful searches for elane have focused on wide-field narrowband surveys or have targeted known sources such as ultraluminous quasi-stellar objects (qsos) or radio galaxies. utilizing groups of coherently strong lyα absorptions, we have developed a new method to identify high-redshift galaxy overdensities and have identified an extremely massive overdensity, boss1441, at z=2{--}3. in its density peak, we discover an elan that is associated with a relatively faint continuum. to date, this object has the highest diffuse lyα nebular luminosity of {l}{nebula}=5.1+/- 0.1× {10}44 erg s-1. above the 2σ surface brightness limit of sb{}{lyα }=4.8× {10}-18 erg s-1 cm-2 arcsec-2, this nebula has an end-to-end spatial extent of 442 kpc. this radio-quiet source also has extended c iv λ 1549 and he ii λ 1640 emission on ≳ 30 {kpc} scales. note that the lyα, he ii, and c iv emissions all have double-peaked line profiles. each velocity component has an fwhm of ≈700-1000 km s-1. we argue that this lyα nebula could be powered by shocks due to an active galactic nucleus-driven outflow or photoionization by a strongly obscured source. | discovery of an enormous lyα nebula in a massive galaxy overdensity at z = 2.3 |
extremely red quasars, with bolometric luminosities exceeding 1047 erg s-1, are a fascinating high-redshift population that is absent in the local universe. they are the best candidates for supermassive black holes accreting at rates at or above the eddington limit, and they are associated with the most rapid and powerful outflows of ionized gas known to date. they are also hosted by massive galaxies. here we present the first integral field unit observations of a high-redshift quasar obtained by the near infrared spectrograph on board the james webb space telescope (jwst), which targeted sdss j165202.64+172852.3, an extremely red quasar at z = 2.94. the jwst observations reveal extended ionized gas-as traced by [o iii] λ5007 å-in the host galaxy of the quasar, its outflow, and the circumgalactic medium. the complex morphology and kinematics imply that the quasar resides in a very dense environment with several interacting companion galaxies within projected distances of 10-15 kpc. the high density of the environment and the large velocities of the companion galaxies suggest that this system may represent the core of a forming cluster of galaxies. the system is a good candidate for a merger of two or more dark matter halos, each with a mass of a few 1013 m ⊙, and potentially traces one of the densest knots at z ~ 3. | first results from the jwst early release science program q3d: turbulent times in the life of a z 3 extremely red quasar revealed by nirspec ifu |
the wide-field infrared survey explorer mission has unveiled a rare population of high-redshift (z = 1-4.6), dusty, hyper-luminous galaxies, with infrared luminosities {{l}ir}\gt {{10}13} {{l}⊙ }, and sometimes exceeding {{10}14} {{l}⊙ }. previous work has shown that their dust temperatures and overall far-infrared spectral energy distributions (seds) are significantly hotter than expected to be powered by star formation. we present here an analysis of the rest-frame optical through mid-infrared seds for a large sample of these so-called “hot, dust-obscured galaxies” (hot dogs). we find that the seds of hot dogs are generally well modeled by the combination of a luminous, yet obscured active galactic nuclei (agns) that dominates the rest-frame emission at λ \gt 1 μ m and the bolometric luminosity output, and a less luminous host galaxy that is responsible for the bulk of the rest optical/uv emission. even though the stellar mass of the host galaxies may be as large as 1011-1012 m⊙, the agn emission, with a range of luminosities comparable to those of the most luminous qsos known, require that either hot dogs have black hole masses significantly in excess of the local relations, or that they radiate significantly above the eddington limit, at a level at least 10 times more efficiently than z ∼ 2 qsos. we show that, while rare, the number density of hot dogs is comparable to that of equally luminous but unobscured (i.e., type 1) qsos. this may be at odds with the trend suggested at lower luminosities for the fraction of obscured agns to decrease with increasing luminosity. that trend may, instead, reverse at higher luminosities. alternatively, hot dogs may not be the torus-obscured counterparts of the known optically selected, largely unobscured, hyper-luminous qsos, and may represent a new component of the galaxy evolution paradigm. finally, we discuss the environments of hot dogs and statistically show that these objects are in regions as dense as those of known high-redshift proto-clusters. | half of the most luminous quasars may be obscured: investigating the nature of wise-selected hot dust-obscured galaxies |
we have conducted a multiwavelength survey of 42 radio loud narrow-1ine seyfert 1 galaxies (rlnls1s), selected by searching among all the known sources of this type and omitting those with steep radio spectra. we analyse data from radio frequencies to x-rays, and supplement these with information available from online catalogues and the literature in order to cover the full electromagnetic spectrum. this is the largest known multiwavelength survey for this type of source. we detected 90% of the sources in x-rays and found 17% at γ rays. extreme variability at high energies was also found, down to timescales as short as hours. in some sources, dramatic spectral and flux changes suggest interplay between a relativistic jet and the accretion disk. the estimated masses of the central black holes are in the range ~106-8 m⊙, lower than those of blazars, while the accretion luminosities span a range from ~0.01 to ~0.49 times the eddington limit, with an outlier at 0.003, similar to those of quasars. the distribution of the calculated jet power spans a range from ~1042.6 to ~1045.6 erg s-1, generally lower than quasars and bl lac objects, but partially overlapping with the latter. once normalised by the mass of the central black holes, the jet power of the three types of active galactic nuclei are consistent with each other, indicating that the jets are similar and the observational differences are due to scaling factors. despite the observational differences, the central engine of rlnls1s is apparently quite similar to that of blazars. the historical difficulties in finding radio-loud narrow-line seyfert 1 galaxies might be due to their low power and to intermittent jetactivity. tables 4-9 and figs. 8-13 are available in electronic form at http://www.aanda.org | properties of flat-spectrum radio-loud narrow-line seyfert 1 galaxies |
we present the largest homogeneous survey of z > 4.4 damped lyα systems (dlas) using the spectra of 163 qsos that comprise the giant gemini gmos (ggg) survey. with this survey we make the most precise high-redshift measurement of the cosmological mass density of neutral hydrogen, ω_{h i}. at such high redshift, important systematic uncertainties in the identification of dlas are produced by strong intergalactic medium absorption and qso continuum placement. these can cause spurious dla detections, result in real dlas being missed or bias the inferred dla column density distribution. we correct for these effects using a combination of mock and higher resolution spectra, and show that for the ggg dla sample the uncertainties introduced are smaller than the statistical errors on ω_{h i}. we find ω_{h i}=0.98^{+0.20}_{-0.18}× 10^{-3} at <z> = 4.9, assuming a 20 per cent contribution from lower column density systems below the dla threshold. by comparing to literature measurements at lower redshifts, we show that ω_{h i} can be described by the functional form ω_{h i}(z)∝ (1+z)^{0.4}. this gradual decrease from z = 5 to 0 is consistent with the bulk of h i gas being a transitory phase fuelling star formation, which is continually replenished by more highly ionized gas from the intergalactic medium and from recycled galactic winds. | the neutral hydrogen cosmological mass density at z = 5 |
the cosmological principle, that the universe is homogeneous and isotropic on sufficiently large scales, underpins the standard model of cosmology. however, a recent analysis of 1.36 million infrared-selected quasars has identified a significant tension in the amplitude of the number-count dipole compared to that derived from the cosmic microwave background (cmb), thus challenging the cosmological principle. here, we present a bayesian analysis of the same quasar sample, testing various hypotheses using the bayesian evidence. we find unambiguous evidence for the presence of a dipole in the distribution of quasars with a direction that is consistent with the dipole identified in the cmb. however, the amplitude of the dipole is found to be 2.7 times larger than that expected from the conventional kinematic explanation of the cmb dipole, with a statistical significance of 5.7σ. to compare these results with theoretical expectations, we sharpen the λcdm predictions for the probability distribution of the amplitude, taking into account a number of observational and theoretical systematics. in particular, we show that the presence of the galactic plane mask causes a considerable loss of dipole signal due to a leakage of power into higher multipoles, exacerbating the discrepancy in the amplitude. by contrast, we show using probabilistic arguments that the source evolution of quasars improves the discrepancy, but only mildly so. these results support the original findings of an anomalously large quasar dipole, independent of the statistical methodology used. | testing the cosmological principle with catwise quasars: a bayesian analysis of the number-count dipole |
we present results of time-series analysis of the first year of the fairall 9 intensive disc-reverberation campaign. we used swift and the las cumbres observatory global telescope network to continuously monitor fairall 9 from x-rays to near-infrared at a daily to subdaily cadence. the cross-correlation function between bands provides evidence for a lag spectrum consistent with the τ ∝ λ4/3 scaling expected for an optically thick, geometrically thin blackbody accretion disc. decomposing the flux into constant and variable components, the variable component's spectral energy distribution is slightly steeper than the standard accretion disc prediction. we find evidence at the balmer edge in both the lag and flux spectra for an additional bound-free continuum contribution that may arise from reprocessing in the broad-line region. the inferred driving light curve suggests two distinct components, a rapidly variable (<4 d) component arising from x-ray reprocessing, and a more slowly varying (>100 d) component with an opposite lag to the reverberation signal. | intensive disc-reverberation mapping of fairall 9: first year of swift and lco monitoring |
the study of the space density of bright active galactic nuclei (agns) at z > 4 has been subject to extensive effort given its importance in the estimation of cosmological ionizing emissivity and growth of supermassive black holes. in this context we have recently derived high space densities of agns at z ∼ 4 and -25 < m 1450 < -23 in the cosmic evolution survey (cosmos) field from a spectroscopically complete sample. in the present paper we attempt to extend the knowledge of the agn space density at fainter magnitudes (-22.5 < m 1450 < -18.5) in the 4 < z < 6.1 redshift interval by means of a multiwavelength sample of galaxies in the cosmic assembly near-ir deep extragalactic legacy survey (candels) goods-south, goods-north, and egs fields. we use an updated criterion to extract faint agns from a population of near-ir (rest-frame uv) selected galaxies at photometric z > 4 showing x-ray detection in deep chandra images available for the three candels fields. we have collected a photometric sample of 32 agn candidates in the selected redshift interval, six of which having spectroscopic redshifts. including our cosmos sample as well as other bright qso samples allows a first guess on the shape of the uv luminosity function (lf) at z ∼ 4.5. the resulting emissivity and photoionization rate appear consistent with that derived from the photoionization level of the intergalactic medium at z ∼ 4.5. an extrapolation to z ∼ 5.6 suggests an important agn contribution to the ionization of intergalactic medium if there are no significant changes in the shape of the uv lf. | space densities and emissivities of active galactic nuclei at z > 4 |
using deep ($11.2\, \rm{h}$) vlt/muse data from the megaflow survey, we report the first detection of extended $\rm{mg\, \small {ii}}$ emission from a galaxy's halo that is probed by a quasar sightline. the $\rm{mg\, \small {ii}}\, \lambda \lambda \, 2796, 2803$ emission around the z = 0.702 galaxy ($\log (m_*/\rm{m_\odot })=10.05_{-0.11}^{+0.15}{}$) is detected out to $\approx 25\, \hbox{kpc}$ from the central galaxy and covers $1.0\times 10^3\, \hbox{kpc}^2$ above a surface brightness of $14\times 10^{-19}\, \rm{erg}\, \rm{s}^{-1}\, \rm{cm}^{-2}\, \rm{arcsec}^{-2}{}$ ($2\, \sigma$; integrated over $1200\, \rm{km\, s}^{-1}= 19\mathring{\rm a}$ and averaged over $1.5\, \rm{arcsec}^{2}$). the $\rm{mg\, \small {ii}}$ emission around this highly inclined galaxy (i ≃ 75 deg) is strongest along the galaxy's projected minor axis, consistent with the $\rm{mg\, \small {ii}}$ gas having been ejected from the galaxy into a bi-conical structure. the quasar sightline, which is aligned with the galaxy's minor axis, shows strong $\rm{mg\, \small {ii}}$ absorption ($\hbox{$ew_0^{\lambda 2796}$}{}=1.8{}\, \mathring{\rm a}$) at an impact parameter of $39{}\, \hbox{kpc}$ from the galaxy. comparing the kinematics of both the emission and the absorption - probed with vlt/uves - to the expectation from a simple toy model of a bi-conical outflow, we find good consistency when assuming a relatively slow outflow ($v_\rm{out}=130{}\, \rm{km\, s}^{-1}$). we investigate potential origins of the extended $\rm{mg\, \small {ii}}$ emission using simple toy models. with continuum scattering models we encounter serious difficulties in explaining the luminosity of the $\rm{mg\, \small {ii}}$ halo and in reconciling density estimates from emission and absorption. instead, we find that shocks might be a more viable source to power the extended $\rm{mg\, \small {ii}}$ (and non-resonant $[\rm{o\, \small {ii}}]$) emission. | muse gas flow and wind (megaflow) viii. discovery of a mgii emission halo probed by a quasar sightline |
the strong intervening absorption system at redshift 1.15 towards the very bright quasar he 0515−4414 is the most studied absorber for measuring possible cosmological variations in the fine-structure constant, α. we observed he 0515−4414 for 16.1 h with the very large telescope and present here the first constraint on relative variations in α with parts-per-million (ppm) precision from the new espresso spectrograph: δα/α = 1.3 ± 1.3stat ± 0.4sys ppm. the statistical uncertainty (1σ) is similar to the ensemble precision of previous large samples of absorbers and derives from the high signal-to-noise ratio achieved (≈105 per 0.4 km s−1 pixel). espresso's design, and the calibration of our observations with its laser frequency comb, effectively removed wavelength calibration errors from our measurement. the high resolving power of our espresso spectrum (r = 145 000) enabled the identification of very narrow components within the absorption profile, allowing a more robust analysis of δα/α. the evidence for the narrow components is corroborated by their correspondence with previously detected molecular hydrogen and neutral carbon. the main remaining systematic errors arise from ambiguities in the absorption profile modelling, effects from redispersing the individual quasar exposures, and convergence of the parameter estimation algorithm. all analyses of the spectrum, including systematic error estimates, were initially blinded to avoid human biases. we make our reduced espresso spectrum of he 0515−4414 publicly available for further analysis. combining our espresso result with 28 measurements, from other spectrographs, in which wavelength calibration errors have been mitigated yields a weighted mean δα/α = −0.5 ± 0.5stat ± 0.4sys ppm at redshifts 0.6−2.4. based on guaranteed time observations collected at the european southern observatory under eso programme 1102.a-0852 by the espresso consortium. based on guaranteed time observations collected at the european southern observatory under eso programme 1102.a-0852 by the espresso consortium. the data and analysis products from this work are publicly available at https://doi.org/10.5281/zenodo.5512490 (<xref ref-type="bibr" rid="r57">murphy et al. 2021</xref>). | fundamental physics with espresso: precise limit on variations in the fine-structure constant towards the bright quasar he 0515−4414 |
supermassive black holes (smbhs) of $\sim 10^9\, \rm m_{\odot }$ are generally believed to be the central engines of the luminous quasars observed at z ≳ 6, but their astrophysical origin remains elusive. to investigate the formation of these distant quasars, we perform a suite of zoom-in simulations on a favourable halo, with a mass of $\sim 10^{13}\, \rm m_{\odot }$ at z = 6 and a history of multiple major mergers, ideal for bh growth. we test bh seeds of $10 {\!-\!} 10^6\, \rm m_{\odot }$, and various accretion and feedback models, including thin-disc and slim-disc accretion. we find that abundant gas supply and efficient angular momentum transport by gravitational torques are critical to bh accretion, and that the final bh mass depends strongly on the seed mass and radiative efficiency which in turn depends on feedback model. in our simulations, heavy seeds of $\gtrsim 10^4\, \rm m_{\odot }$ can grow rapidly to smbhs of $10^8 {\!-\!} 10^9\, \rm m_{\odot }$ by z ~6 in both thin and slim disc accretion models, provided that the duty cycle of near-eddington accretion with an eddington ratio λedd ≳ 0.6 is maintained at $\gtrsim 40{{\ \rm per\ cent}}$. in particular, for a $10^5\, \rm m_{\odot }$ seed, both our fiducial model and the supercritical accretion model with no spin produce bright quasars with smbhs of $\sim 10^9\, \rm m_{\odot }$ at z ~ 7.5. on the other hand, the light seeds of $\lesssim 10^3\, \rm m_{\odot }$ failed to grow to $10^8\, \rm m_{\odot }$ by z ~ 6 in our simulations. we caution that the results are inconclusive due to limitations of our numerical methods and physical models, and we stress the need for further investigations on the growth of bh seeds with more advanced methods. | the formation of the first quasars: the black hole seeds, accretion, and feedback models |
using vlti/gravity and sinfoni data, we investigate the subparsec gas and dust structure around the nearby type 1 active galactic nucleus (agn) hosted by ngc 3783. the k-band coverage of gravity uniquely allows simultaneous analysis of the size and kinematics of the broad line region (blr), the size and structure of the near-infrared(near-ir)-continuum-emitting hot dust, and the size of the coronal line region (clr). we find the blr, probed through broad brγ emission, to be well described by a rotating, thick disc with a radial distribution of clouds peaking in the inner region. in our blr model, the physical mean radius of 16 light-days is nearly twice the ten-day time-lag that would be measured, which closely matches the ten-day time-lag that has been measured by reverberation mapping. we measure a hot dust full-width at half-maximum (fwhm) size of 0.74 mas (0.14 pc) and further reconstruct an image of the hot dust, which reveals a faint (5% of the total flux) offset cloud that we interpret as an accreting or outflowing cloud heated by the central agn. finally, we directly measure the fwhm size of the nuclear clr as traced by the [ca viii] and narrow brγ line. we find a fwhm size of 2.2 mas (0.4 pc), fully in line with the expectation of the clr located between the blr and narrow line region. combining all of these measurements together with larger scale near-ir integral field unit and mid-ir interferometry data, we are able to comprehensively map the structure and dynamics of gas and dust from 0.01 to 100 pc. gravity is developed in a collaboration by the max planck institute for extraterrestrial physics, lesia of observatoire de paris/université psl/cnrs/sorbonne université/université de paris and ipag of université grenoble alpes/cnrs, the max planck institute for astronomy, the university of cologne, the centra - centro de astrofisica e gravitação, and the european southern observatory. | the central parsec of ngc 3783: a rotating broad emission line region, asymmetric hot dust structure, and compact coronal line region |
we used the hubble space telescope (hst) wide field camera 3 (wfc3) near-infrared camera to image the host galaxies of a sample of 11 luminous, dust-reddened quasars at z∼ 2—the peak epoch of black hole growth and star formation in the universe—to test the merger-driven picture for the coevolution of galaxies and their nuclear black holes. the red quasars come from the first+2mass red quasar survey and a newer, deeper, ukidss+first sample. these dust-reddened quasars are the most intrinsically luminous quasars in the universe at all redshifts, and they may represent the dust-clearing transitional phase in the merger-driven black hole growth scenario. probing the host galaxies in rest-frame visible light, the hst images reveal that 8/10 of these quasars have actively merging hosts, whereas one source is reddened by an intervening lower-redshift galaxy along the line of sight. we study the morphological properties of the quasar hosts using parametric sérsic fits, as well as nonparametric estimators (gini coefficient, m20, and asymmetry). their properties are heterogeneous but broadly consistent with the most extreme morphologies of local merging systems such as ultraluminous infrared galaxies. the red quasars have a luminosity range of {log}({l}{bol})=47.8-48.3 (erg s-1), and the merger fraction of their hosts is consistent with merger-driven models of luminous active galactic nuclei activity at z = 2, which supports the picture in which luminous quasars and galaxies coevolve through major mergers that trigger both star formation and black hole growth. based on go observations made with the nasa/esa hubble space telescope, as well as from the data archive at the space telescope science institute, which is operated by the association of universities for research in astronomy, inc., under nasa contract nas 5-26555. these observations are associated with program # 12942. | major mergers host the most-luminous red quasars at z ~ 2: a hubble space telescope wfc3/ir study |
jwst is unveiling for the first time accreting black holes (bhs) with masses of 106 - 107 m⊙ at z > 4, with the most distant residing in gnz11 at z = 10.6. are we really surprised to find them in the nuclei of z ≃ 5 - 11 galaxies? here we predict the properties of 4 < z < 11 bhs and their host galaxies considering an eddington-limited (el) and a super-eddington (se) bh accretion scenario, using the cosmic archaeology tool (cat) semi-analytical model. we calculate the transmitted spectral energy distribution of cat synthetic candidates, representative of the bh/galaxy properties of gnz11. we also examine the possibility that the z = 8.7 galaxy ceers-1019 could host an active bh. we find that the luminosity of high-z jwst detected bhs are better reproduced by the se model, where bhs descend from efficiently growing light and heavy seeds. conversely, the host galaxy stellar masses are better matched in the el model, in which all the systems detectable with jwst surveys jades and ceers descend from heavy bh seeds. we support the interpretation that the central point source of gnz11 could be powered by a se (λedd ≃ 2 - 3) accreting bh with mass 1.5 × 106 m⊙, while the emission from ceers-1019 is dominated by the host galaxy; if it harbours an active bh, we find it to have a mass of mbh ≃ 107 m⊙, and to be accreting at sub-eddington rates (λedd ≃ 0.5). | are we surprised to find smbhs with jwst at z ≥ 9? |
using a new recently compiled milliarcsecond compact radio data set of 120 intermediate-luminosity quasars in the redshift range 0.46< z <2.76, whose statistical linear sizes show negligible dependence on redshifts and intrinsic luminosity and thus represent standard rulers in cosmology, we constrain three viable and most popular f( t) gravity models, where t is the torsion scalar in teleparallel gravity. our analysis reveals that constraining power of the quasars data (n=120) is comparable to the union2.1 sn ia data (n=580) for all three f( t) models. together with other standard ruler probes such as cosmic microwave background and baryon acoustic oscillation distance measurements, the present value of the matter density parameter ω _m obtained by quasars is much larger than that derived from other observations. for one of the models considered (f_1cdm) a small but noticeable deviation from λ cdm cosmology is present, while in the framework of f_3cdm the effective equation of state may cross the phantom divide line at lower redshifts. these results indicate that intermediate-luminosity quasars could provide an effective observational probe comparable to sn ia at much higher redshifts, and f( t) gravity is a reasonable candidate for the modified gravity theory. | new observational constraints on f( t) cosmology from radio quasars |
we construct an analytic phenomenological model for extended warm/hot gaseous coronae of l* galaxies. we consider uv o vi cosmic origins spectrograph (cos)-halos absorption line data in combination with milky way (mw) x-ray o vii and o viii absorption and emission. we fit these data with a single model representing the cos-halos galaxies and a galactic corona. our model is multi-phased, with hot and warm gas components, each with a (turbulent) log-normal distribution of temperatures and densities. the hot gas, traced by the x-ray absorption and emission, is in hydrostatic equilibrium in an mw gravitational potential. the median temperature of the hot gas is 1.5× {10}6 k and the mean hydrogen density is ∼ 5× {10}-5 {{cm}}-3. the warm component as traced by the o vi, is gas that has cooled out of the high density tail of the hot component. the total warm/hot gas mass is high and is 1.2× {10}11 {m}⊙ . the gas metallicity we require to reproduce the oxygen ion column densities is 0.5 solar. the warm o vi component has a short cooling time (∼ 2× {10}8 years), as hinted by observations. the hot component, however, is ∼ 80 % of the total gas mass and is relatively long-lived, with {t}{cool}∼ 7× {10}9 years. our model supports suggestions that hot galactic coronae can contain significant amounts of gas. these reservoirs may enable galaxies to continue forming stars steadily for long periods of time and account for “missing baryons” in galaxies in the local universe. | massive warm/hot galaxy coronae as probed by uv/x-ray oxygen absorption and emission. i. basic model |
the 3d velocities of m31 and m33 are important for understanding the evolution and cosmological context of the local group. their most massive stars are detected by gaia, and we use data release 2 (dr2) to determine the galaxy proper motions (pms). we select galaxy members based on, e.g., parallax, pm, color-magnitude diagram location, and local stellar density. the pm rotation of both galaxies is confidently detected, consistent with the known line-of-sight rotation curves: {v}rot}=-206+/- 86 {km} {{{s}}}-1 (counterclockwise) for m31, and {v}rot}=80 +/- 52 {km} {{{s}}}-1 (clockwise) for m33. we measure the center-of-mass pm of each galaxy relative to surrounding background quasars in dr2. this yields that ({μ }α * ,{μ }δ ) equals (65+/- 18,-57+/- 15) μ {as} {yr}}-1 for m31 and (31+/- 19,-29+/- 16) μ {as} {yr}}-1 for m33. in addition to the listed random errors, each component has an additional residual systematic error of 16 μ {as} {yr}}-1. these results are consistent at 0.8σ and 1.0σ with the (2 and 3 times higher accuracy) measurements already available from hubble space telescope (hst) optical imaging and very long baseline array water maser observations, respectively. this lends confidence that all these measurements are robust. the new results imply that the m31 orbit toward the milky way (mw) is somewhat less radial than previously inferred, {v}\tan ,{dr2+{hst}}={57}-31+35 {km} {{{s}}}-1, and strengthen arguments that m33 may be on its first infall into m31. the results highlight the future potential of gaia for pm studies beyond the mw satellite system. | first gaia dynamics of the andromeda system: dr2 proper motions, orbits, and rotation of m31 and m33 |
when the light from a distant object passes very near to a foreground galaxy or cluster, gravitational lensing can cause it to appear as multiple images on the sky1. if the source is variable, it can be used to constrain the cosmic expansion rate2 and dark energy models3. achieving these cosmological goals requires many lensed transients with precise time-delay measurements4. lensed supernovae are attractive for this purpose because they have relatively simple photometric behaviour, with well-understood light curve shapes and colours—in contrast to the stochastic variation of quasars. here we report the discovery of a multiply imaged supernova, at 2016jka (`sn requiem'). it appeared in an evolved galaxy at redshift 1.95, gravitationally lensed by a foreground galaxy cluster5. it is probably a type ia supernova—the explosion of a low-mass stellar remnant, whose light curve can be used to measure cosmic distances. in archival hubble space telescope imaging, three lensed images of the supernova are detected with relative time delays of <200 d. we predict that a fourth image will appear close to the cluster core in the year 2037 ± 2. observation of the fourth image could provide a time-delay precision of ~7 d, <1% of the extraordinary 20 yr baseline. the supernova classification and the predicted reappearance time could be improved with further lens modelling and a comprehensive analysis of systematic uncertainties. | a gravitationally lensed supernova with an observable two-decade time delay |
we explore the origin of fast molecular outflows that have been observed in active galactic nuclei (agns). previous numerical studies have shown that it is difficult to create such an outflow by accelerating existing molecular clouds in the host galaxy, as the clouds will be destroyed before they can reach the high velocities that are observed. in this work, we consider an alternative scenario where molecules form in situ within the agn outflow. we present a series of hydro-chemical simulations of an isotropic agn wind interacting with a uniform medium. we follow the time-dependent chemistry of 157 species, including 20 molecules, to determine whether molecules can form rapidly enough to produce the observed molecular outflows. we find h2 outflow rates up to 140 m_{⊙} yr^{-1}, which is sensitive to density, agn luminosity, and metallicity. we compute emission and absorption lines of co, oh, and warm (a few hundred k) h2 from the simulations in post-processing. the co-derived outflow rates and oh absorption strengths at solar metallicity agree with observations, although the maximum line-of-sight velocities from the model co spectra are a factor ≈2 lower than is observed. we derive a co (1-0) to h2 conversion factor of α _{co (1-0)} = 0.13 m_{⊙} (k km s^{-1} pc2)^{-1}, 6 times lower than is commonly assumed in observations of such systems. we find strong emission from the mid-infrared lines of h2. the mass of h2 traced by this infrared emission is within a few per cent of the total h2 mass. this h2 emission may be observable by james webb space telescope. | the origin of fast molecular outflows in quasars: molecule formation in agn-driven galactic winds |
cosmological models and their parameters are widely debated because of theoretical and observational mismatches of the standard cosmological model, especially the current discrepancy between the value of the hubble constant, h 0, obtained by type ia supernovae (sne ia), and the cosmic microwave background radiation (cmb). thus, considering high-redshift probes like quasars (qsos), having intermediate redshifts between sne ia and cmb, is a necessary step. in this work, we use sne ia and the most updated qso sample, reaching redshifts up to z ~ 7.5, applying the risaliti-lusso qso relation based on a nonlinear relation between ultraviolet and x-ray luminosities. we consider this relation both in its original form and corrected for selection biases and evolution in redshift through a reliable statistical method also accounting for the circularity problem. we also explore two approaches: with and without calibration on sne ia. we then investigate flat and nonflat standard cosmological models and a flat wcdm model, with a constant dark energy equation-of-state parameter w. remarkably, when correcting for the evolution as a function of cosmology, we obtain closed constraints on ω musing only noncalibrated qsos. we find that considering noncalibrated qsos combined with sne ia and accounting for the same correction, our results are compatible with a flat λcdm model with ω m= 0.3 and h 0 = 70 km s-1 mpc-1. intriguingly, the h 0 values obtained are placed halfway between the one from sne ia and cmb, paving the way for new insights into the h 0 tension. | a bias-free cosmological analysis with quasars alleviating h 0 tension |
context. x-ray emission from quasars (qsos) has been used to assess supermassive black hole accretion properties up to z ≈ 6. however, at z > 6 only ≈15 qsos are covered by sensitive x-ray observations, preventing a statistically significant investigation of the x-ray properties of the qso population in the first gyr of the universe.aims: we present new chandra observations of a sample of 10 z > 6 qsos, selected to have virial black-hole mass estimates from mg ii line spectroscopy (log {mbh}/{m_⊙}=8.5-9.6) . adding archival x-ray data for an additional 15 z > 6 qsos, we investigate the x-ray properties of the qso population in the first gyr of the universe. in particular, we focus on the luv - lx relation, which is traced by the αox parameter, and the shape of their x-ray spectra.methods: we performed photometric analyses to derive estimates of the x-ray luminosities of our z > 6 qsos, and thus their αox values and bolometric corrections (kbol = lbol/lx). we compared the resulting αox and kbol distributions with the results found for qso samples at lower redshift, and ran several statistical tests to check for a possible evolution of the luv - lx relation. finally, we performed a basic x-ray spectral analysis of the brightest z > 6 qsos to derive their individual photon indices, and joint spectral analysis of the whole sample to estimate the average photon index.results: we detect seven of the new chandra targets in at least one standard energy band, while two more are detected discarding energies e > 5 kev, where background dominates. we confirm a lack of significant evolution of αox with redshift, which extends the results from previous works up to z > 6 with a statistically significant qso sample. furthermore, we confirm the trend of an increasing bolometric correction with increasing luminosity found for qsos at lower redshifts. the average power-law photon index of our sample (⟨γ⟩ = 2.20-0.34+0.39 and ⟨γ⟩ = 2.13-0.13+0.13 for sources with < 30 and > 30 net counts, respectively) is slightly steeper than, but still consistent with, typical qsos at z = 1 - 6.conclusions: all of these results indicate a lack of substantial evolution of the inner accretion-disk and hot-corona structure in qsos from low redshift to z > 6. our data hint at generally high eddington ratios at z > 6. | the x-ray properties of z > 6 quasars: no evident evolution of accretion physics in the first gyr of the universe |
giant radio galaxies (grgs) are a subclass of radio galaxies, which have grown to megaparsec scales. grgs are much rarer than normal-sized radio galaxies (< 0.7 mpc) and the reason for their gigantic sizes is still debated. here, we report on the biggest sample of grgs identified to date. these objects were found in the lofar two-metre sky survey first data release images, which cover a 424 deg2 region. of the 239 grgs found, 225 are new discoveries. the grgs in our sample have sizes ranging from 0.7 mpc to 3.5 mpc and have redshifts (z) between 0.1 and 2.3. seven grgs have sizes above 2 mpc and one has a size of ∼3.5 mpc. the sample contains 40 grgs hosted by spectroscopically confirmed quasars. here, we present the search techniques employed and the resulting catalogue of the newly discovered large sample of grgs along with their radio properties. in this paper, we also show for the first time that the spectral index of grgs is similar to that of normal-sized radio galaxies, indicating that most of the grg population is not dead or is not similar to a remnant-type radio galaxy. we find that 20 out of 239 grgs in our sample are located at the centres of clusters and we present our analysis on their cluster environment and radio morphology. the sample of giant radio galaxies is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/635/a5 | giant radio galaxies in the lofar two-metre sky survey. i. radio and environmental properties |
the longstanding search for the cosmological model that best describes the universe has been made more intriguing since the recent discovery of the hubble constant, h0, tension observed between the value of h0 from the cosmic microwave background and from type ia supernovae (sne ia). hence, the commonly trusted flat λ cold dark matter (λcdm) model is under investigation. in this scenario, cosmography is a very powerful technique to investigate the evolution of the universe without any cosmological assumption, thus revealing tensions between observational data and predictions from cosmological models in a completely model-independent way. we here employ a robust cosmographic technique based on an orthogonal logarithmic polynomial expansion of the luminosity distance to fit quasars (qsos) alone and qsos combined with gamma-ray bursts (grbs), sne ia, and baryon acoustic oscillations. to apply qsos and grbs as probes we use, respectively, the risaliti-lusso relation between ultraviolet and x-ray luminosities and the 'dainotti grb 3d relation' among the rest-frame end time of the x-ray plateau emission, its corresponding luminosity, and the peak prompt luminosity. we also correct qsos and grbs for selection biases and redshift evolution and we employ both the traditional gaussian likelihood and the newly discovered best-fitting likelihoods for each probe investigated. this comprehensive analysis reveals a strong tension ($\gt 4 \, \sigma$) between our data sets and the flat λcdm model proving the power of both the cosmographic approach and high-redshift sources, such as qsos and grbs, which can probe the universe at early epochs. | tensions with the flat λcdm model from high-redshift cosmography |
several models have predicted that stars could form inside galactic outflows and that this would be a new major mode of galaxy evolution. observations of galactic outflows have revealed that they host large amounts of dense and clumpy molecular gas, which provide conditions suitable for star formation. we have investigated the properties of the outflows in a large sample of galaxies by exploiting the integral field spectroscopic data of the large manga-sdss4 galaxy survey. we find evidence for prominent star formation occurring inside at least 30 per cent of the galactic outflows in our sample, whilst signs of star formation are seen in up to half of the outflows. we also show that even if star formation is prominent inside many other galactic outflows, this may have not been revealed as the diagnostics are easily dominated by the presence of even faint active galactic nucleus and shocks. if very massive outflows typical of distant galaxies and quasars follow the same scaling relations observed locally, then the star formation inside high-z outflows can be up to several 100 m_{\odot } yr^{-1} and could contribute substantially to the early formation of the spheroidal component of galaxies. star formation in outflows can also potentially contribute to establishing the scaling relations between black holes and their host spheroids. moreover, supernovae exploding on large orbits can chemically enrich in situ and heat the circumgalactic and intergalactic medium. finally, young stars ejected on large orbits may also contribute to the reionization of the universe. | widespread star formation inside galactic outflows |
we use high-resolution cosmological zoom-in simulations from the fire (feedback in realistic environments) project to make predictions for the covering fractions of neutral hydrogen around galaxies at z = 2-4. these simulations resolve the interstellar medium of galaxies and explicitly implement a comprehensive set of stellar feedback mechanisms. our simulation sample consists of 16 main haloes covering the mass range mh ≈ 109-6 × 1012 m⊙ at z = 2, including 12 haloes in the mass range mh ∼ 1011-1012 m⊙ corresponding to lyman break galaxies (lbgs). we process our simulations with a ray tracing method to compute the ionization state of the gas. galactic winds increase the h i covering fractions in galaxy haloes by direct ejection of cool gas from galaxies and through interactions with gas inflowing from the intergalactic medium. our simulations predict h i covering fractions for lyman limit systems (llss) consistent with measurements around z ∼ 2-2.5 lbgs; these covering fractions are a factor ∼2 higher than our previous calculations without galactic winds. the fractions of h i absorbers arising in inflows and in outflows are on average ∼50 per cent but exhibit significant time variability, ranging from ∼10 to ∼90 per cent. for our most massive haloes, we find a factor ∼3 deficit in the lls covering fraction relative to what is measured around quasars at z ∼ 2, suggesting that the presence of a quasar may affect the properties of halo gas on ∼100 kpc scales. the predicted covering fractions, which decrease with time, peak at mh ∼ 1011-1012 m⊙, near the peak of the star formation efficiency in dark matter haloes. in our simulations, star formation and galactic outflows are highly time dependent; h i covering fractions are also time variable but less so because they represent averages over large areas. | neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history |
in large-scale cosmological hydrodynamic simulations simplified sub-grid models for gas accretion on to black holes and agn feedback are commonly used. such models typically depend on various free parameters, which are not well constrained. we present a new advanced model containing a more detailed description of agn feedback, where those parameters reflect the results of recent observations. the model takes the dependence of these parameters on the black hole properties into account and describes a continuous transition between the feedback processes acting in the so-called radio-mode and quasar-mode. in addition, we implement a more detailed description of the accretion of gas on to black holes by distinguishing between hot and cold gas accretion. our new implementations prevent black holes from gaining too much mass, particularly at low redshifts, so that our simulations are successful in reproducing the observed present-day black hole mass function. our new model also suppresses star formation in massive galaxies slightly more efficiently than many state-of-the-art models. therefore, the simulations that include our new implementations produce a more realistic population of quiescent and star-forming galaxies compared to recent observations, even if some discrepancies remain. in addition, the baryon conversion efficiencies in our simulation are - except for the high-mass end - consistent with observations presented in the literature over the mass range resolved by our simulations. finally, we discuss the significant impact of the feedback model on the low-luminous end of the agn luminosity function. | a refined sub-grid model for black hole accretion and agn feedback in large cosmological simulations |
the uncertain origin of the recently discovered “changing-look” quasar phenomenon—in which a luminous quasar dims significantly to a quiescent state in repeat spectroscopy over ∼10-year timescales—may present unexpected challenges to our understanding of quasar accretion. to better understand this phenomenon, we take a first step toward building a sample of changing-look quasars with a systematic but simple archival search for these objects in the sloan digital sky survey data release 12. by leveraging the >10-year baselines for objects with repeat spectroscopy, we uncover two new changing-look quasars and a third discovered previously. decomposition of the multiepoch spectra and analysis of the broad emission lines suggest that the quasar accretion disk emission dims because of rapidly decreasing accretion rates (by factors of ≳2.5), while disfavoring changes in intrinsic dust extinction for the two objects where these analyses are possible. broad emission line energetics also support intrinsic dimming of quasar emission as the origin for this phenomenon rather than transient tidal disruption events or supernovae. although our search criteria included quasars at all redshifts and transitions from either quasar-like to galaxy-like states or the reverse, all of the clear cases of changing-look quasars discovered were at relatively low redshift (z∼ 0.2{--}0.3) and only exhibit quasar-like to galaxy-like transitions. | toward an understanding of changing-look quasars: an archival spectroscopic search in sdss |
the brightness of an active galactic nucleus is set by the gas falling onto it from the galaxy, and the gas infall rate is regulated by the brightness of the active galactic nucleus; this feedback loop is the process by which supermassive black holes in the centres of galaxies may moderate the growth of their hosts. gas outflows (in the form of disk winds) release huge quantities of energy into the interstellar medium, potentially clearing the surrounding gas. the most extreme (in terms of speed and energy) of these—the ultrafast outflows—are the subset of x-ray-detected outflows with velocities higher than 10,000 kilometres per second, believed to originate in relativistic (that is, near the speed of light) disk winds a few hundred gravitational radii from the black hole. the absorption features produced by these outflows are variable, but no clear link has been found between the behaviour of the x-ray continuum and the velocity or optical depth of the outflows, owing to the long timescales of quasar variability. here we report the observation of multiple absorption lines from an extreme ultrafast gas flow in the x-ray spectrum of the active galactic nucleus iras 13224-3809, at 0.236 ± 0.006 times the speed of light (71,000 kilometres per second), where the absorption is strongly anti-correlated with the emission of x-rays from the inner regions of the accretion disk. if the gas flow is identified as a genuine outflow then it is in the fastest five per cent of such winds, and its variability is hundreds of times faster than in other variable winds, allowing us to observe in hours what would take months in a quasar. we find x-ray spectral signatures of the wind simultaneously in both low- and high-energy detectors, suggesting a single ionized outflow, linking the low- and high-energy absorption lines. that this disk wind is responding to the emission from the inner accretion disk demonstrates a connection between accretion processes occurring on very different scales: the x-ray emission from within a few gravitational radii of the black hole ionizing the disk wind hundreds of gravitational radii further away as the x-ray flux rises. | the response of relativistic outflowing gas to the inner accretion disk of a black hole |
we present 1.4 pc resolution observations of 256 ghz nuclear radio continuum and hcn (j = 3 → 2) in the molecular torus of ngc 1068. the integrated radio continuum emission has a flat spectrum consistent with free-free emission and resolves into an x-shaped structure resembling an edge-brightened bicone. hcn is detected in absorption against the continuum, and the absorption spectrum shows a pronounced blue wing that suggests a high-velocity molecular outflow with speeds reaching 450 km s-1. analysis of the off-nucleus emission line kinematics and morphology reveals two nested, rotating disk components. the inner disk, inside r ∼ 1.2 pc, has kinematics that are consistent with the nearly edge-on, geometrically thin h2o megamaser disk in keplerian rotation around a central mass of 1.66 × 107 m ⊙. the outer disk, which extends to ∼7 pc radius, counter-rotates relative to the inner disk. the rotation curve of the outer disk is consistent with rotation around the same central mass as the megamaser disk but in the opposite sense. the morphology of the molecular gas is asymmetric around the nuclear continuum source. we speculate that the outer disk formed from more recently introduced molecular gas falling out of the host galaxy or from a captured dwarf satellite galaxy. in ngc 1068, we find direct evidence that the molecular torus consists of counter-rotating and misaligned disks on parsec scales. | counter-rotation and high-velocity outflow in the parsec-scale molecular torus of ngc 1068 |
we make use of recent developments in the analysis of galaxy redshift surveys to present an easy to use matrix-based analysis framework for the galaxy power spectrum multipoles, including wide-angle effects and the survey window function. we employ this framework to derive the deconvolved power spectrum multipoles of 6dfgs dr3, boss dr12 and the eboss dr16 quasar sample. as an alternative to the standard analysis, the deconvolved power spectrum multipoles can be used to perform a data analysis agnostic of survey specific aspects, like the window function. we show that in the case of the boss dataset, the baryon acoustic oscillation (bao) analysis using the deconvolved power spectra results in the same likelihood as the standard analysis. to facilitate the analysis based on both the convolved and deconvolved power spectrum measurements, we provide the window function matrices, wide-angle matrices, covariance matrices and the power spectrum multipole measurements for the datasets mentioned above. together with this paper we publish a python-based toolbox to calculate the different analysis components. the appendix contains a detailed user guide with examples for how a cosmological analysis of these datasets could be implemented. we hope that our work makes the analysis of galaxy survey datasets more accessible to the wider cosmology community. | unified galaxy power spectrum measurements from 6dfgs, boss, and eboss |
the james webb space telescope will have the power to characterize high-redshift quasars at z ≥ 6 with an unprecedented depth and spatial resolution. while the brightest quasars at such redshift (i.e. with bolometric luminosity $l_{\rm bol}\geqslant 10^{46}\, \rm erg/s$) provide us with key information on the most extreme objects in the universe, measuring the black hole (bh) mass and eddington ratios of fainter quasars with $l_{\rm bol}= 10^{45}-10^{46}\, \rm erg\,s^{ -1}$ opens a path to understand the build-up of more normal bhs at z ≥ 6. in this paper, we show that the illustris, tng100, tng300, horizon-agn, eagle, and simba large-scale cosmological simulations do not agree on whether bhs at z ≥ 4 are overmassive or undermassive at fixed galaxy stellar mass with respect to the mbh - m⋆ scaling relation at z = 0 (bh mass offsets). our conclusions are unchanged when using the local scaling relation produced by each simulation or empirical relations. we find that the bh mass offsets of the simulated faint quasar population at z ≥ 4, unlike those of bright quasars, represent the bh mass offsets of the entire bh population, for all the simulations. thus, a population of faint quasars with $l_{\rm bol}= 10^{45}-10^{46}\, \rm erg\,s^{ -1}$ observed by jwst can provide key constraints on the assembly of bhs at high redshift. moreover, this will help constraining the high-redshift regime of cosmological simulations, including bh seeding, early growth, and co-evolution with the host galaxies. our results also motivate the need for simulations of larger cosmological volumes down to z ~ 6, with the same diversity of subgrid physics, in order to gain statistics on the most extreme objects at high redshift. | co-evolution of massive black holes and their host galaxies at high redshift: discrepancies from six cosmological simulations and the key role of jwst |
the growth rate and expansion history of the universe can be measured from large galaxy redshift surveys using the alcock-paczynski effect. we validate the redshift space distortion models used in the final analysis of the sloan digital sky survey (sdss) extended baryon oscillation spectroscopic survey (eboss) data release 16 quasar clustering sample, in configuration and fourier space, using a series of halo occupation distribution mock catalogues generated using the outerrim n-body simulation. we test three models on a series of non-blind mocks, in the outerrim cosmology, and blind mocks, which have been rescaled to new cosmologies, and investigate the effects of redshift smearing and catastrophic redshifts. we find that for the non-blind mocks, the models are able to recover fσ8 to within 3 per cent and α∥ and α⊥ to within 1 per cent. the scatter in the measurements is larger for the blind mocks, due to the assumption of an incorrect fiducial cosmology. from this mock challenge, we find that all three models perform well, with similar systematic errors on fσ8, α∥, and α⊥ at the level of $\sigma _{f\sigma _8}=0.013$, $\sigma _{\alpha _\parallel }=0.012$, and $\sigma _{\alpha _\bot }=0.008$. the systematic error on the combined consensus is $\sigma _{f\sigma _8}=0.011$, $\sigma _{\alpha _\parallel }=0.008$, and $\sigma _{\alpha _\bot }=0.005$, which is used in the final dr16 analysis. for baryon acoustic oscillation fits in configuration and fourier space, we take conservative systematic errors of $\sigma _{\alpha _\parallel }=0.010$ and $\sigma _{\alpha _\bot }=0.007$. | the completed sdss-iv extended baryon oscillation spectroscopic survey: n-body mock challenge for the quasar sample |
rapid, large amplitude variability at optical to x-ray wavelengths is now seen in an increasing number of seyfert galaxies and luminous quasars. the variations imply a global change in accretion power, but are too rapid to be communicated by inflow through a standard thin accretion disc. such discs are long known to have difficulty explaining the observed optical/uv emission from active galactic nuclei. here we show that alternative models developed to explain these observations have larger scale heights and shorter inflow times. accretion discs supported by magnetic pressure in particular are geometrically thick at all luminosities, with inflow times as short as the observed few year time-scales in extreme variability events to date. future time-resolved, multiwavelength observations can distinguish between inflow through a geometrically thick disc as proposed here, and alternative scenarios of extreme reprocessing of a central source or instability-driven limit cycles. | extreme agn variability: evidence of magnetically elevated accretion? |
we measure the effective optical depth of he ii lyα absorption {τ }{eff,{he}{{ii}}} at 2.3\lt z\lt 3.5 in 17 uv-transmitting quasars observed with uv spectrographs on the hubble space telescope. the median {τ }{eff,{he}{{ii}}} values increase gradually from 1.95 at z=2.7 to 5.17 at z=3.4, but with a strong sightline-to-sightline variance. many ≃ 35 comoving mpc regions of the z\gt 3 intergalactic medium (igm) remain transmissive ({τ }{eff,{he}{{ii}}}\lt 4), and the gradual trend with redshift appears consistent with density evolution of a fully reionized igm. these modest optical depths imply average he ii fractions of {x}{he{{ii}}}\lt 0.01 and he ii ionizing photon mean free paths of ≃ 50 comoving mpc at z≃ 3.4, thus requiring that a substantial volume of the helium in the universe was already doubly ionized at early times; this stands in conflict with current models of he ii reionization driven by luminous quasars. along 10 sightlines we measure the coeval h i lyα effective optical depths, allowing us to study the density dependence of {τ }{eff,{he}{{ii}}} at z∼ 3. we establish that the dependence of {τ }{eff,{he}{{ii}}} on increasing {τ }{eff,{{h}}{{i}}} is significantly shallower than expected from simple models of an igm reionized in he ii. this requires higher he ii photoionization rates in overdense regions or underdense regions being not in photoionization equilibrium. moreover, there are very large fluctuations in {τ }{eff,{he}{{ii}}} at all {τ }{eff,{{h}}{{i}}} which greatly exceed the expectations from these simple models. these data present a distinct challenge to scenarios of he ii reionization—an igm where he ii appears to be predominantly ionized at z≃ 3.4, and with a radiation field strength that may be correlated with the density field, but exhibits large fluctuations at all densities. based on observations made with the nasa/esa hubble space telescope (hst), obtained at the space telescope science institute, which is operated by the association of universities for research in astronomy, inc., under nasa contract nas5-26555. these observations are associated with program #11742. archival hst data (#7575, 9350, 11528, 12178, 12249) were obtained from the mikulski archive for space telescopes (mast). several hst programs provided ancillary calibration data (#11860, 11895, 12414, 12423, 12716, 12775, 12870, 13108). some of the data presented herein were obtained at the w.m. keck observatory, which is operated as a scientific partnership among the california institute of technology, the university of california and nasa; it was made possible by the generous financial support of the w.m. keck foundation. based on observations made with eso telescopes at the la silla paranal observatory under program ids 166.a-0106, 071.a-0066 and 083.a-0421. | early and extended helium reionization over more than 600 million years of cosmic time |
faint star-forming galaxies at z ∼ 2-3 can be used as alternative background sources to probe the lyα forest in addition to quasars, yielding high sightline densities that enable 3d tomographic reconstruction of the foreground absorption field. here, we present the first data release from the cosmos lyα mapping and tomography observations (clamato) survey, which was conducted with the lris spectrograph on the keck i telescope. over an observational footprint of 0.157 deg2 within the cosmos field, we used 240 galaxies and quasars at 2.17 < z < 3.00, with a mean comoving transverse separation of 2.37 {h}-1 {mpc}, as background sources probing the foreground lyα forest absorption at 2.05 < z < 2.55. the lyα forest data was then used to create a wiener-filtered tomographic reconstruction over a comoving volume of 3.15 × {10}5 {h}-3 {mpc}}3 with an effective smoothing scale of 2.5 {h}-1 {mpc}. in addition to traditional figures, this map is also presented as a virtual-reality visualization and manipulable interactive figure. we see large overdensities and underdensities that visually agree with the distribution of coeval galaxies from spectroscopic redshift surveys in the same field, including overdensities associated with several recently discovered galaxy protoclusters in the volume. quantitatively, the map signal-to-noise is {{s}}/{{{n}}}wiener}≈ 3.4 over a 3 h -1mpc top-hat kernel based on the variances estimated from the wiener filter. this data release includes the redshift catalog, reduced spectra, extracted lyα forest pixel data, and reconstructed tomographic map of the absorption. these can be downloaded from zenodo (10.5281/zenodo.1292459). | first data release of the cosmos lyα mapping and tomography observations: 3d lyα forest tomography at 2.05 < z < 2.55 |
context. the need to analyze the available large synoptic multi-band surveys drives the development of new data-analysis methods. photometric redshift estimation is one field of application where such new methods improved the results, substantially. up to now, the vast majority of applied redshift estimation methods have utilized photometric features.aims: we aim to develop a method to derive probabilistic photometric redshift directly from multi-band imaging data, rendering pre-classification of objects and feature extraction obsolete.methods: a modified version of a deep convolutional network was combined with a mixture density network. the estimates are expressed as gaussian mixture models representing the probability density functions (pdfs) in the redshift space. in addition to the traditional scores, the continuous ranked probability score (crps) and the probability integral transform (pit) were applied as performance criteria. we have adopted a feature based random forest and a plain mixture density network to compare performances on experiments with data from sdss (dr9).results: we show that the proposed method is able to predict redshift pdfs independently from the type of source, for example galaxies, quasars or stars. thereby the prediction performance is better than both presented reference methods and is comparable to results from the literature.conclusions: the presented method is extremely general and allows us to solve of any kind of probabilistic regression problems based on imaging data, for example estimating metallicity or star formation rate of galaxies. this kind of methodology is tremendously important for the next generation of surveys. | photometric redshift estimation via deep learning. generalized and pre-classification-less, image based, fully probabilistic redshifts |
negative feedback from active galactic nuclei (agn) is considered a key mechanism in shaping galaxy evolution. fast, extended outflows are frequently detected in the agn host galaxies at all redshifts and luminosities, both in ionised and molecular gas. however, these outflows are only potentially able to quench star formation, and we are still lacking decisive evidence of negative feedback in action. here we present observations obtained with the spectrograph for integral field observations in the near infrared (sinfoni) h- and k-band integral-field of two quasars at z ~ 2.4 that are characterised by fast, extended outflows detected through the [oiii]λ5007 line. the high signal-to-noise ratio of our observations allows us to identify faint narrow (fwhm< 500 km s-1) and spatially extended components in [oiii]λ5007 and hα emission associated with star formation in the host galaxy. this star formation powered emission is spatially anti-correlated with the fast outflows. the ionised outflows therefore appear to be able to suppress star formation in the region where the outflow is expanding. however, the detection of narrow spatially extended hα emission indicates star formation rates of at least ~50-90 m⊙ yr-1, suggesting either that agn feedback does not affect the whole galaxy or that many feedback episodes are required before star formation is completely quenched. on the other hand, the narrow hα emission extending along the edges of the outflow cone may also lead also to a positive feedback interpretation. our results highlight the possible double role of galaxy-wide outflows in host galaxy evolution. based on observations collected at the european organisation for astronomical research in the southern hemisphere, chile, p.id: 086.b-0579(a) and 091.a-0261(a).the reduced data cubes are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/591/a28 | fast outflows and star formation quenching in quasar host galaxies |
we use h ii starburst galaxy apparent magnitude measurements to constrain cosmological parameters in six cosmological models. a joint analysis of h ii galaxy, quasar angular size, baryon acoustic oscillations peak length scale, and hubble parameter measurements result in relatively model-independent and restrictive estimates of the current values of the non-relativistic matter density parameter $\omega _{\rm m_0}$ and the hubble constant h0. these estimates favour a 2.0-3.4σ (depending on cosmological model) lower h0 than what is measured from the local expansion rate. the combined data are consistent with dark energy being a cosmological constant and with flat spatial hypersurfaces, but do not strongly rule out mild dark energy dynamics or slightly non-flat spatial geometries. | cosmological constraints from h ii starburst galaxy apparent magnitude and other cosmological measurements |
klioner et al. have used the gaia edr3 data to directly measure the solar system's acceleration within the milky way using the apparent proper motions of quasars. here i show that this single absolute acceleration measurement in combination with relative accelerations obtained from pulsar orbital decay allows one to determine all of the parameters describing the dynamics of our local galactic environment, including the circular velocity at the sun $v_0 = 244 \pm 8$ km/s and its derivative $v'_0 = 2 \pm 9$ km/s/kpc, the local angular frequency, the oort constants, and the sun's motion with respect to the lsr. this is the first determination of these parameters that only uses the general theory of relativity without the need for additional assumptions. | a purely acceleration-based measurement of the fundamental galactic parameters |
nuclear star clusters (nscs) and supermassive black holes (smbhs) both inhabit galactic nuclei, coexisting in a range of bulge masses, but excluding each other in the largest or smallest galaxies. we propose that the transformation of nscs into smbhs occurs via runaway tidal captures, once nscs exceed a certain critical central density and velocity dispersion. the bottleneck in this process is growing the first e-fold in black hole mass. the growth of a stellar mass black hole past this bottleneck occurs as tidally captured stars are consumed in repeated episodes of mass transfer at pericentre. tidal captures may deactivate as a growth channel once the black hole mass ≳102-3 m⊙, but tidal disruption events will continue and can grow the seed smbh to larger sizes. the runaway slows (becomes subexponential) once the seed smbh consumes the core of its host nsc. while most of the cosmic mass density in smbhs is ultimately produced by episodic gaseous accretion in very massive galaxies, the smallest smbhs have probably grown from strong tidal encounters with nsc stars. smbh seeds that grow for a time t entirely through this channel will follow simple power-law relations with the velocity dispersion, σ, of their host galaxy. in the simplest regime, it is m_\bullet ∼ σ ^{3/2}√{m_\star t / g} ∼ 106 m_{⊙} (σ / 50 {km s}^{-1})^{3/2}(t/10^{10} yr)^{1/2}, but the exponents and pre-factor can differ slightly depending on the details of loss cone refilling. current tidal disruption event rates predicted from this mechanism are consistent with observations. | formation of massive black holes in galactic nuclei: runaway tidal encounters |
the lyman alpha (ly α) line of hydrogen is a prominent feature in the spectra of star-forming galaxies, usually redshifted by a few hundreds of km s-1 compared to the systemic redshift. this large offset hampers follow-up surveys, galaxy pair statistics, and correlations with quasar absorption lines when only ly α is available. we propose diagnostics that can be used to recover the systemic redshift directly from the properties of the ly α line profile. we use spectroscopic observations of ly α emitters for which a precise measurement of the systemic redshift is available. our sample contains 13 sources detected between z ≈ 3 and z ≈ 6 as part of various multi-unit spectroscopic explorer guaranteed time observations. we also include a compilation of spectroscopic ly α data from the literature spanning a wide redshift range (z ≈ 0-8). first, restricting our analysis to double-peaked ly α spectra, we find a tight correlation between the velocity offset of the red peak with respect to the systemic redshift, v_peak^red, and the separation of the peaks. secondly, we find a correlation between v_peak^red and the full width at half-maximum of the ly α line. fitting formulas to estimate systemic redshifts of galaxies with an accuracy of ≤100 km s-1, when only the ly α emission line is available, are given for the two methods. | recovering the systemic redshift of galaxies from their lyman alpha line profile |
we present 20 wide-field infrared survey explorer (wise)-selected galaxies with bolometric luminosities lbol > 1014 l⊙, including five with infrared luminosities lir ≡ l(rest 8-1000 μm) > 1014 l⊙. these “extremely luminous infrared galaxies,” or elirgs, were discovered using the “w1w2-dropout” selection criteria which requires marginal or non-detections at 3.4 and 4.6 μm (w1 and w2, respectively) but strong detections at 12 and 22 μm in the wise survey. their spectral energy distributions are dominated by emission at rest-frame 4-10 μm, suggesting that hot dust with td ∼ 450 k is responsible for the high luminosities. these galaxies are likely powered by highly obscured active galactic nuclei (agns), and there is no evidence suggesting these systems are beamed or lensed. we compare this wise-selected sample with 116 optically selected quasars that reach the same lbol level, corresponding to the most luminous unobscured quasars in the literature. we find that the rest-frame 5.8 and 7.8 μm luminosities of the wise-selected elirgs can be 30%-80% higher than that of the unobscured quasars. the existence of agns with lbol > 1014 l⊙ at z > 3 suggests that these supermassive black holes are born with large mass, or have very rapid mass assembly. for black hole seed masses ∼103 m⊙, either sustained super-eddington accretion is needed, or the radiative efficiency must be <15%, implying a black hole with slow spin, possibly due to chaotic accretion. | the most luminous galaxies discovered by wise |
observations of $z \gtrsim 6$ quasars provide information on the early phases of the most massive black holes (mbhs) and galaxies. current observations, able to trace both gas and stellar properties, show that most mbhs at high redshift seem overmassive compared to the local population, in line with the elliptical galaxy population, or even above, thus implying a very rapid growth of these objects. to assess the physical conditions for such a rapid growth and explain the existence of a population of already mature mbhs when the universe was less than 1~gyr old, we here explore whether episodes of accretion above the eddington limit can occur across cosmic epochs. by employing state-of-the-art high-resolution cosmological zoom-in simulations of a $z\sim 7$ quasar, where different accretion regimes are consistently included, together with their associated radiative and kinetic feedback, we show that super-eddington phases can be sustained for relatively long time-scales (tens of myr) and discuss how they affect the growth of mbhs. we also show, by means of a semi-analytic evolution, that the mbh spin remains relatively low during super-eddington phases, and this would result in a lower feedback efficiency, hence a potentially faster growth that might then explain the overmassiveness of high-redshift mbhs. | sustained super-eddington accretion in high-redshift quasars |
broad absorption line (bal) quasars are characterized by gas clouds that absorb flux at the wavelength of common quasar spectral features, although blueshifted by velocities that can exceed 0.1c. bal features are interesting as signatures of significant feedback, yet they can also compromise cosmological studies with quasars through their impact on accurate redshifts and measurements of the matter density distribution traced by the lyman-alpha forest. the presence of bals can also significantly contaminate the shape of the most prominent quasar emission lines and introduce systematic shifts in quasar redshifts. we present a catalog of bal quasars discovered in the dark energy spectroscopic instrument (desi) survey early data release, which were observed as part of desi survey validation, as well as the first two months of the main survey. we describe our method to automatically identify bal quasars in desi data, the quantities we measure for each bal, and investigate the completeness and purity of this method with mock desi observations. we mask the wavelengths of the bal features and recompute the quasar redshifts, and find the new redshifts differ by 243 km/s on average for the bal quasar sample. these new, more accurate redshifts are important to obtain the best measurements of quasar clustering, especially at small scales. finally, we present some spectra of rarer classes of bals that illustrate the potential of desi data to identify such populations for further study. | broad absorption line quasars in the dark energy spectroscopic instrument early data release |
cosmic (hydrogen) reionization marks one of the major phase transitions of the universe at redshift z ≥ 6. during this epoch, hydrogen atoms in the intergalactic medium were ionized by lyman continuum (lyc) photons. however, it remains challenging to identify the major sources of the lyc photons responsible for reionization. in particular, individual contributions of quasars (or active galactic nuclei) and galaxies are still under debate. here we construct the far-ultraviolet luminosity function for type 1 quasars at z ≥ 6 that spans 10 magnitudes (−19 ≤ muv ≤ −29), conclusively showing that quasars made a negligible contribution to reionization. we mainly search for quasars in the low-luminosity range of muv > −23 mag that is critical for determination of the total lyc photon production of quasars but has been barely explored previously. we find that the quasar population can only provide less than 7% (95% confidence level) of the total photons needed to keep the universe ionized at z = 6.0-6.6. our result suggests that galaxies, presumably low-luminosity star-forming systems, are the major sources of hydrogen reionization. | definitive upper bound on the negligible contribution of quasars to cosmic reionization |
we present atacama large millimeter/submillimeter array [c ii] 158 μm line and underlying far-infrared (fir) continuum emission observations (0"70 × 0"56 resolution) toward hsc j124353.93+010038.5 (j1243+0100) at z = 7.07, the only low-luminosity (m1450 > -25 mag) quasar currently known at z > 7. the fir continuum is bright (1.52 mjy) and resolved with a total luminosity of lfir = 3.5 × 1012 l⊙. the spatially extended component is responsible for ~40% of the emission. the area-integrated [c ii] spectrum shows a broad wing (fwhm = 997 km s-1, l[c ii] = 1.2 × 109 l⊙), as well as a bright core (fwhm = 235 km s-1, l[c ii] = 1.9 × 109 l⊙). this wing is the first detection of a galactic-scale quasar-driven outflow (atomic outflow rate >447 m⊙ yr-1) at z > 7. the estimated large mass-loading factor of the total outflow (e.g., ≳9 relative to the [c ii]-based star formation rate) suggests that this outflow will soon quench the star formation of the host. the core gas dynamics are governed by rotation, with a rotation curve suggestive of a compact bulge (~3.3 × 1010 m⊙), although it is not yet spatially resolved. finally, we found that j1243+0100 has a black hole mass-to-dynamical mass (and -to-bulge mass) ratio of ~0.4% (~1%), consistent with the local value within the uncertainties. our results therefore suggest that the black hole-host coevolution relation is already in place at z ~ 7 for this object. | subaru high-z exploration of low-luminosity quasars (shellqs). xiii. large-scale feedback and star formation in a low-luminosity quasar at z = 7.07 on the local black hole to host mass relation |
baryon acoustic oscillations (bao) involve measuring the spatial distribution of galaxies to determine the growth rate of cosmic structures. we derive constraints on cosmological parameters from 17 uncorrelated bao measurements that were collected from 333 published data points in the effective redshift range 0.106 ≤ z ≤ 2.36. we test the correlation of the subset using a random covariance matrix. the λ cold dark matter (λcdm) model fit yields the cosmological parameters ωm = 0.261 ± 0.028 and ωλ = 0.733 ± 0.021. combining the bao data with the cosmic chronometers data, the pantheon type ia supernova, and the hubble diagram of gamma-ray bursts and quasars, the hubble constant yields 69.85 ± 1.27 km s-1 mpc-1 and the sound horizon distance gives 146.1 ± 2.15 mpc. beyond the λcdm model we test ωkcdm and wcdm. the spatial curvature is ωk = -0.076 ± 0.012 and the dark energy equation of states is w = -0.989 ± 0.049. we perform the akaike information criteria test to compare the three models, and see that λcdm scores best. the python files with the dataset and the fit package can be found at https://github.com/benidav/bao-2020. | testing late-time cosmic acceleration with uncorrelated baryon acoustic oscillation dataset |
the python qso fitting code (pyqsofit) measures spectral properties of quasars. based on shen's idl version, this code decomposes different components in the quasar spectrum, e.g., host galaxy, power-law continuum, fe ii component, and emission lines. in addition, it can run monto carlo iterations using flux randomization to estimate the uncertainties. | pyqsofit: python code to fit the spectrum of quasars |
we report the discovery of 41 new high-z quasars and luminous galaxies that were spectroscopically identified at 5.7 ≤ z ≤ 6.9. this is the fourth in a series of papers from the subaru high-z exploration of low-luminosity quasars (shellqs) project, based on the deep multi-band imaging data collected by the hyper suprime-cam (hsc) subaru strategic program survey. we selected the photometric candidates using a bayesian probabilistic algorithm and then carried out follow-up spectroscopy with the gran telescopio canarias and the subaru telescope. combined with the sample presented in the previous papers, we have now spectroscopically identified 137 extremely red hsc sources over about 650 deg2, which includes 64 high-z quasars, 24 high-z luminous galaxies, 6 [o iii] emitters at z ∼ 0.8, and 43 galactic cool dwarfs (low-mass stars and brown dwarfs). the new quasars span in luminosity range from m 1450 ∼ -26 to -22 mag, and continue to populate luminosities a few magnitudes lower than have been probed by previous wide-field surveys. in a companion paper, we derive the quasar luminosity function at z ∼ 6 over an unprecedentedly wide range of m 1450 ∼ -28 to -21 mag, exploiting the shellqs and other survey outcomes. | subaru high-z exploration of low-luminosity quasars (shellqs). iv. discovery of 41 quasars and luminous galaxies at 5.7 ≤ z ≤ 6.9 |
the merger of two or more galaxies can enhance the inflow of material from galactic scales into the close environments of active galactic nuclei (agns), obscuring and feeding the supermassive black hole (smbh). both recent simulations and observations of agn in mergers have confirmed that mergers are related to strong nuclear obscuration. however, it is still unclear how agn obscuration evolves in the last phases of the merger process. we study a sample of 60 luminous and ultra-luminous ir galaxies (u/lirgs) from the goals sample observed by nustar. we find that the fraction of agns that are compton thick (ct; $n_{\rm h}\ge 10^{24}\rm \, cm^{-2}$) peaks at $74_{-19}^{+14}{{\ \rm per\ cent}}$ at a late merger stage, prior to coalescence, when the nuclei have projected separations (dsep) of 0.4-6 kpc. a similar peak is also observed in the median nh [$(1.6\pm 0.5)\times 10^{24}\rm \, cm^{-2}$]. the vast majority ($85^{+7}_{-9}{{\ \rm per\ cent}}$) of the agns in the final merger stages (dsep ≲ 10 kpc) are heavily obscured ($n_{\rm h}\ge 10^{23}\rm \, cm^{-2}$), and the median nh of the accreting smbhs in our sample is systematically higher than that of local hard x-ray-selected agn, regardless of the merger stage. this implies that these objects have very obscured nuclear environments, with the $n_{\rm h}\ge 10^{23}\rm \, cm^{-2}$ gas almost completely covering the agn in late mergers. ct agns tend to have systematically higher absorption-corrected x-ray luminosities than less obscured sources. this could either be due to an evolutionary effect, with more obscured sources accreting more rapidly because they have more gas available in their surroundings, or to a selection bias. the latter scenario would imply that we are still missing a large fraction of heavily obscured, lower luminosity ($l_{2-10}\lesssim 10^{43}\rm \, erg\, s^{-1}$) agns in u/lirgs. | a hard x-ray view of luminous and ultra-luminous infrared galaxies in goals - i. agn obscuration along the merger sequence |
the result presented by the boss-sdss collaboration measuring the baryon acoustic oscillations of the lyman-alpha forest from high-redshift quasars indicates a 2.5 σ departure from the standard λ -cold-dark-matter model. this is the first time that the evolution of dark energy at high redshifts has been measured, and the current results cannot be explained by simple generalizations of the cosmological constant. we show here that a simple phenomenological interaction in the dark sector provides a good explanation for this deviation, naturally accommodating the hubble parameter obtained by boss, h (z =2.34 )=222 ±7 km s-1 mpc-1 . by performing a global fit of the parameters with the inclusion of this new data set together with the planck data for the interacting model, we are able to show that some interacting models have constraints for h (2.34 ) and da(2.34 ) that are compatible with the ones obtained by the boss collaboration, showing a better concordance than λ cdm . we also show that the interacting models that have a small positive coupling constant, which helps alleviate the coincidence problem, are compatible with the cosmological observations. adding the likelihood of these new baryon acoustic oscillations data shows an improvement in the global fit, although it is not statistically significant. the coupling constant could not be fully constrained by the data sets used, but the dark energy equation of state shows a slight preference for a value different from a cosmological constant. | evidence for interacting dark energy from boss |
we introduce quasarnet, a deep convolutional neural network that performs classification and redshift estimation of astrophysical spectra with human-expert accuracy. we pose these two tasks as a \emph{feature detection} problem: presence or absence of spectral features determines the class, and their wavelength determines the redshift, very much like human-experts proceed. when ran on boss data to identify quasars through their emission lines, quasarnet defines a sample $99.51\pm0.03$\% pure and $99.52\pm0.03$\% complete, well above the requirements of many analyses using these data. quasarnet significantly reduces the problem of line-confusion that induces catastrophic redshift failures to below 0.2\%. we also extend quasarnet to classify spectra with broad absorption line (bal) features, achieving an accuracy of $98.0\pm0.4$\% for recognizing bal and $97.0\pm0.2$\% for rejecting non-bal quasars. quasarnet is trained on data of low signal-to-noise and medium resolution, typical of current and future astrophysical surveys, and could be easily applied to classify spectra from current and upcoming surveys such as eboss, desi and 4most. | quasarnet: human-level spectral classification and redshifting with deep neural networks |
strong-gravitational lens systems with quadruply imaged quasars (quads) are unique probes to address several fundamental problems in cosmology and astrophysics. although they are intrinsically very rare, ongoing and planned wide-field deep-sky surveys are set to discover thousands of such systems in the next decade. it is thus paramount to devise a general framework to model strong-lens systems to cope with this large influx without being limited by expert investigator time. we propose such a general modelling framework (implemented with the publicly available software lenstronomy) and apply it to uniformly model three-band hubble space telescope wide field camera 3 images of 13 quads. this is the largest uniformly modelled sample of quads to date and paves the way for a variety of studies. to illustrate the scientific content of the sample, we investigate the alignment between the mass and light distribution in the deflectors. the position angles of these distributions are well-aligned, except when there is strong external shear. however, we find no correlation between the ellipticity of the light and mass distributions. we also show that the observed flux-ratios between the images depart significantly from the predictions of simple smooth models. the departures are strongest in the bluest band, consistent with microlensing being the dominant cause in addition to millilensing. future papers will exploit this rich data set in combination with ground-based spectroscopy and time delays to determine quantities such as the hubble constant, the free streaming length of dark matter, and the normalization of the initial stellar mass function. | is every strong lens model unhappy in its own way? uniform modelling of a sample of 13 quadruply+ imaged quasars |
we present a study of the environment of 27 z = 3-4.5 bright quasars from the muse analysis of gas around galaxies (magg) survey. with medium-depth multi unit spectroscopic explorer (muse) observations (4 h on target per field), we characterize the effects of quasars on their surroundings by studying simultaneously the properties of extended gas nebulae and ly α emitters (laes) in the quasar host haloes. we detect extended (up to ≈100 kpc) ly α emission around all magg quasars, finding a very weak redshift evolution between z = 3 and z = 6. by stacking the muse datacubes, we confidently detect extended emission of c iv and only marginally detect extended he ii up to ≈40 kpc, implying that the gas is metal enriched. moreover, our observations show a significant overdensity of laes within 300 $\rm km~s^{-1}$ from the quasar systemic redshifts estimated from the nebular emission. the luminosity functions and equivalent width distributions of these laes show similar shapes with respect to laes away from quasars suggesting that the ly α emission of the majority of these sources is not significantly boosted by the quasar radiation or other processes related to the quasar environment. within this framework, the observed lae overdensities and our kinematic measurements imply that bright quasars at z = 3-4.5 are hosted by haloes in the mass range $\approx 10^{12.0}\small{--}10^{12.5}~\rm m_\odot$ . | muse analysis of gas around galaxies (magg) - iii. the gas and galaxy environment of z = 3-4.5 quasars |
we study the statistics of the lyα forest in a flat λ cold dark matter cosmology with the n-body + eulerian hydrodynamics code nyx. we produce a suite of simulations, covering the observationally relevant redshift range 2 ≤ z ≤ 4. we find that a grid resolution of 20 h-1 kpc is required to produce 1 per cent convergence of lyα forest flux statistics, up to k = 10 h-1 mpc. in addition to establishing resolution requirements, we study the effects of missing modes in these simulations, and find that box sizes of l > 40h-1 mpc are needed to suppress numerical errors to a sub-per cent level. our optically thin simulations with the ionizing background prescription of haardt & madau reproduce an intergalactic medium density-temperature relation with t0 ≈ 104 k and γ ≈ 1.55 at z = 2, with a mean transmitted flux close to the observed values. when using the ionizing background prescription of faucher-giguère et al., the mean flux is 10-15 per cent below observed values at z = 2, and a factor of 2 too small at z = 4. we show the effects of the common practice of rescaling optical depths to the observed mean flux and how it affects convergence rates. we also investigate the practice of `splicing' results from a number of different simulations to estimate the 1d flux power spectrum and show it is accurate at the 10 per cent level. finally, we find that collisional heating of the gas from dark matter particles is negligible in modern cosmological simulations. | the lyman α forest in optically thin hydrodynamical simulations |
the observed high covering fractions of neutral hydrogen (h i) with column densities above ∼1017 cm-2 around lyman-break galaxies (lbgs) and bright quasars at redshifts z ∼ 2-3 has been identified as a challenge for simulations of galaxy formation. we use the evolution and assembly of galaxies and their environment (eagle) cosmological, hydrodynamical simulation, which has been shown to reproduce a wide range of galaxy properties and for which the subgrid feedback was calibrated without considering gas properties, to study the distribution of h i around high-redshift galaxies. we predict the covering fractions of strong h i absorbers (n_{h i}≳ 10^{17} cm^{-2}) inside haloes to increase rapidly with redshift but to depend only weakly on halo mass. for massive (m200 ≳ 1012m⊙) haloes, the covering fraction profiles are nearly scale-invariant and we provide fitting functions that reproduce the simulation results. while efficient feedback is required to increase the h i covering fractions to the high observed values, the distribution of strong absorbers in and around haloes of a fixed mass is insensitive to factor of 2 variations in the strength of the stellar feedback. in contrast, at fixed stellar mass the predicted h i distribution is highly sensitive to the feedback efficiency. the fiducial eagle simulation reproduces both the observed global column density distribution function of h i and the observed radial covering fraction profiles of strong h i absorbers around lbgs and bright quasars. | the distribution of neutral hydrogen around high-redshift galaxies and quasars in the eagle simulation |
evidence for bright-radio blazars being high-energy neutrino sources was found in recent years. however, specifics of how and where these particles get produced still need to be determined. in this paper, we add 14 new icecube events from 2020-2022 to update our analysis of the neutrino-blazars connection. we test and refine earlier findings by utilizing the total of 71 track-like high-energy icecube events from 2009-2022. we correlate them with the complete sample of 3412 extragalactic radio sources selected by their compact radio emission. we demonstrate that neutrinos are statistically associated with radio-bright blazars with a post-trial p-value of 3 · 10-4. in addition to this statistical study, we confirm previous individual neutrino-blazar associations, find and discuss several new ones. notably, pks 1741 - 038 was selected earlier and had a second neutrino detected from its direction in 2022; pks 0735 + 168 has experienced a major flare across the whole electromagnetic spectrum coincidently with a neutrino arrival from that direction in 2021. | growing evidence for high-energy neutrinos originating in radio blazars |
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