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we present the second data release of the cosmos lyα mapping and tomography observations survey conducted with the low resolution imaging spectrometer on the keck i telescope. this project used lyα forest absorption in the spectra of faint star-forming galaxies and quasars at z ~ 2-3 to trace neutral hydrogen in the intergalactic medium. in particular, we use 320 objects over a footprint of ~0.2 deg2 to reconstruct the absorption field at 2.05 < z < 2.55 at ~2 h -1 mpc resolution. we apply a wiener filtering technique to the observed data to reconstruct three-dimensional (3d) maps of the field over a volume of 4.1 × 105 h -3 mpc3. in addition to the filtered flux maps, for the first time we infer the underlying dark matter field through a forward-modeling framework from a joint likelihood of galaxy and lyα forest data, finding clear examples of the detailed cosmic web consisting of cosmic voids, sheets, filaments, and nodes. in addition to traditional figures, we present a number of interactive 3d models to allow exploration of the data and qualitative comparisons to known galaxy surveys. we find that our inferred overdensities are consistent with those found from galaxy fields. we will make all our reduced spectra, extracted lyα forest pixel data, and reconstructed tomographic maps publicly available upon publication. | second data release of the cosmos lyα mapping and tomography observations: the first 3d maps of the detailed cosmic web at 2.05 < z < 2.55 |
we present the accretion disc-size estimates for a sample of 19 active galactic nuclei (agns) using the optical g-, r-, and i-band light curves obtained from the zwicky transient facility survey. all the agns have reliable supermassive black hole (smbh) mass estimates based on previous reverberation mapping measurements. the multiband light curves are cross-correlated, and the reverberation lag is estimated using the interpolated cross-correlation function method and the bayesian method using the javelin code. as expected from the disc-reprocessing arguments, the g - r band lags are shorter than the g - i band lags for this sample. the interband lags for all, but five sources, are larger than the sizes predicted from the standard shakura sunyaev (ss) analytical model. we fit the light curves directly using a thin disc model implemented through the javelin code to get the accretion disc sizes. the disc sizes obtained using this model are on an average 3.9 times larger than the prediction based on the ss disc model. we find a weak correlation between the disc sizes and the known physical parameters, namely the luminosity and the smbh mass. in the near future, a large sample of agns covering broader ranges of luminosity and smbh mass from large photometric surveys would be helpful in a better understanding of the structure and physics of the accretion disc. | accretion disc sizes from continuum reverberation mapping of agn selected from the ztf survey |
broad-line regions (blrs) in high-redshift quasars provide crucial information on chemical enrichment in the early universe. here we present a study of blr metallicities in 33 quasars at redshift 5.7 < z < 6.4. using the near-ir spectra of the quasars obtained from the gemini telescope, we measure their rest-frame uv emission-line flux and calculate flux ratios. we then estimate blr metallicities with empirical calibrations based on photoionization models. the inferred median metallicity of our sample is a few times the solar value, indicating that the blr gas had been highly metal enriched at z ~ 6. we compare our sample with a low-redshift quasar sample with similar luminosities and find no evidence of redshift evolution in quasar blr metallicities. this is consistent with previous studies. the fe ii/mg ii flux ratio, a proxy for the fe/α element abundance ratio, shows no redshift evolution as well, further supporting rapid nuclear star formation at z ~ 6. we also find that the black hole mass-blr metallicity relation at z ~ 6 is consistent with the relation measured at 2 < z < 5, suggesting that our results are not biased by a selection effect due to this relation. | metallicity in quasar broad-line regions at redshift 6 |
luminous quasars are powerful targets to investigate the role of feedback from supermassive black holes (bhs) in regulating the growth phases of bhs themselves and of their host galaxies, up to the highest redshifts. here we investigate the cosmic evolution of the occurrence and kinematics of bh-driven outflows, as traced by broad absorption line (bal) features, due to the c iv ionic transition. we exploit a sample of 1935 quasars at z = 2.1-6.6 with bolometric luminosity log(l bol/erg s-1) ≳ 46.5, drawn from the sloan digital sky survey and from the x-shooter legacy survey of quasars at the reionization epoch (xqr-30). we consider rest-frame optical bright quasars to minimize observational biases due to quasar selection criteria. we apply a homogeneous bal-identification analysis, based on employing composite template spectra to estimate the quasar intrinsic emission. we find a bal quasar fraction close to 20% at z ~ 2-4, while it increases to almost 50% at z ~ 6. the velocity and width of the bal features also increase at z ≳ 4.5. we exclude the possibility that the redshift evolution of the bal properties is due to differences in terms of quasar luminosity and accretion rate. these results suggest significant bh feedback occurring in the 1 gyr old universe, likely affecting the growth of bhs and, possibly, of their host galaxies, as supported by models of early bh and galaxy evolution. | the fraction and kinematics of broad absorption line quasars across cosmic time |
this article gives a brief historical introduction and reviews our current understanding of jets in radio galaxies and quasars from an observational perspective, with an emphasis on observations at radio wavelengths. recent results on the fanaroff-riley (fr) classification scheme, and the nature of radio structures and jets in the fr classes as well as in high-excitation and low-excitation radio galaxies are summarized. the collimation and propagation of jets from nuclear sub-pc to hundreds of kpc scales from both observational and theoretical works have been discussed. the jets exhibit evidence of interaction with a clumpy interstellar medium, especially in young radio sources, and could trigger both star formation as well as suppress star formation depending on the physical conditions. observational evidence for such interactions and jet feedback which have profound implications our understanding of galaxy evolution have been presented. recurrent jet activity which has been seen over a wide range of projected linear size and time scales has been discussed. this review article concludes with a brief discussion of unresolved questions on jets which new telescopes should help address. | jets in radio galaxies and quasars: an observational perspective |
aims: the modelling of spectroscopic observations of tidal disruption events (tdes) to date suggests that the newly formed accretion disks are mostly quasi-circular. in this work we study the transient event at 2020zso, hosted by an active galactic nucleus (agn; as inferred from narrow emission line diagnostics), with the aim of characterising the properties of its newly formed accretion flow.methods: we classify at 2020zso as a tde based on the blackbody evolution inferred from uv/optical photometric observations and spectral line content and evolution. we identify transient, double-peaked bowen (n iii), he i, he ii, and hα emission lines. we model medium-resolution optical spectroscopy of the he ii (after careful de-blending of the n iii contribution) and hα lines during the rise, peak, and early decline of the light curve using relativistic, elliptical accretion disk models.results: we find that the spectral evolution before the peak can be explained by optical depth effects consistent with an outflowing, optically thick eddington envelope. around the peak, the envelope reaches its maximum extent (approximately 1015 cm, or ∼3000-6000 gravitational radii for an inferred black hole mass of 5−10 × 105 m⊙) and becomes optically thin. the hα and he ii emission lines at and after the peak can be reproduced with a highly inclined (i = 85 ± 5 degrees), highly elliptical (e = 0.97 ± 0.01), and relatively compact (rin = several 100 rg and rout = several 1000 rg) accretion disk.conclusions: overall, the line profiles suggest a highly elliptical geometry for the new accretion flow, consistent with theoretical expectations of newly formed tde disks. we quantitatively confirm, for the first time, the high inclination nature of a bowen (and x-ray dim) tde, consistent with the unification picture of tdes, where the inclination largely determines the observational appearance. rapid line profile variations rule out the binary supermassive black hole hypothesis as the origin of the eccentricity; these results thus provide a direct link between a tde in an agn and the eccentric accretion disk. we illustrate for the first time how optical spectroscopy can be used to constrain the black hole spin, through (the lack of) disk precession signatures (changes in inferred inclination). we constrain the disk alignment timescale to > 15 days in at2020zso, which rules out high black hole spin values (a < 0.8) for mbh ∼ 106 m⊙ and disk viscosity α ≳ 0.1. | an elliptical accretion disk following the tidal disruption event at 2020zso |
to elucidate the intrinsic broadband infrared (ir) emission properties of active galactic nuclei (agns), we analyze the spectral energy distributions (seds) of 87 z ≲ 0.5 palomar-green (pg) quasars. while the elvis agn template with a moderate far-ir correction can reasonably match the seds of the agn components in ∼60% of the sample (and is superior to alternatives such as that by assef), it fails on two quasar populations: (1) hot-dust-deficient (hdd) quasars that show very weak emission thoroughly from the near-ir to the far-ir, and (2) warm-dust-deficient (wdd) quasars that have similar hot dust emission as normal quasars but are relatively faint in the mid- and far-ir. after building composite agn templates for these dust-deficient quasars, we successfully fit the 0.3-500 μm seds of the pg sample with the appropriate agn template, an infrared template of a star-forming galaxy, and a host galaxy stellar template. 20 hdd and 12 wdd quasars are identified from the sed decomposition, including seven ambiguous cases. compared with normal quasars, the hdd quasars have agns with relatively low eddington ratios and the fraction of wdd quasars increases with agn luminosity. moreover, both the hdd and wdd quasar populations show relatively stronger mid-ir silicate emission. virtually identical sed properties are also found in some quasars from z = 0.5 to 6. we propose a conceptual model to demonstrate that the observed dust deficiency of quasars can result from a change of structures of the circumnuclear tori that can occur at any cosmic epoch. | dust-deficient palomar-green quasars and the diversity of agn intrinsic ir emission |
we present the serendipitous discovery of a 'giant arc on the sky' at $z$ ~ 0.8. the giant arc (ga) spans ~1 gpc (proper size, present epoch) and appears to be almost symmetrical on the sky. it was discovered via intervening mg ii absorbers in the spectra of background quasars, using the catalogues of zhu & ménard. the use of mg ii absorbers represents a new approach to the investigation of large-scale structures (lsss) at redshifts $0.45 \la z \la 2.25$. we present the observational properties of the ga, and we assess it statistically using methods based on (i) single-linkage hierarchical clustering (~4.5σ); (ii) the cuzick-edwards test (~3.0σ); and (iii) power-spectrum analysis (~4.8σ). each of these methods has distinctive attributes and powers, and we advise considering the evidence from the ensemble. we discuss our approaches to mitigating any post hoc aspects of analysing significance after discovery. the overdensity of the ga is δρ/ρ ~ 1.3 ± 0.3. the ga is the newest and one of the largest of a steadily accumulating set of very large lsss that may (cautiously) challenge the cosmological principle, upon which the 'standard model' of cosmology is founded. conceivably, the ga is the precursor of a structure like the sloan great wall (but the ga is about twice the size), seen when the universe was about half its present age. | a giant arc on the sky |
we estimate the accretion rates onto the supermassive black holes that power 20 of the highest-redshift quasars, at z≳ 5.8, including the quasar with the highest redshift known to date—ulas j1120 at z = 7.09. the analysis is based on the observed (rest-frame) optical luminosities and reliable “virial” estimates of the bh masses of the quasars, and utilizes scaling relations derived from thin accretion disk theory. the mass accretion rates through the postulated disks cover a wide range, {\dot{m}}{disk}≃ 4{--}190 {m}⊙{{yr}}-1, with most of the objects (80%) having {\dot{m}}{disk}≃ 10{--}65 {m}⊙{{yr}}-1, confirming the eddington-limited nature of the accretion flows. by combining our estimates of {\dot{m}}{disk} with conservative, lower limits on the bolometric luminosities of the quasars, we investigate which alternative values of η best account for all the available data. we find that the vast majority of quasars (∼85%) can be explained with radiative efficiencies in the range η ≃ 0.03{--}0.3, with a median value close to the commonly assumed η = 0.1. within this range, we obtain conservative estimates of η ≳ 0.14 for ulas j1120 and sdss j0100 (at z = 6.3), and of ≳ 0.19 for sdss j1148 (at z=6.41; assuming their bh masses are accurate). the implied accretion timescales are generally in the range {t}{acc}\equiv {m}{bh}/{\dot{m}}{bh}≃ 0.1{--}1 {gyr}, suggesting that most quasars could have had ∼ 1{--}10 mass e-foldings since bh seed formation. our analysis therefore demonstrates that the available luminosities and masses for the highest-redshift quasars can be explained self-consistently within the thin, radiatively efficient accretion disk paradigm. episodes of radiatively inefficient, “super-critical” accretion may have occurred at significantly earlier epochs (i.e., z≳ 10). | on the accretion rates and radiative efficiencies of the highest-redshift quasars |
i show that there is a physical limit to the mass of a black hole, above which it cannot grow through luminous accretion of gas, and so cannot appear as a quasar or active galactic nucleus (agn). the limit is mmax ≃ 5 × 1010 m⊙ for typical parameters, but can reach mmax ≃ 2.7 × 1011 m⊙ in extreme cases (e.g. maximal prograde spin). the largest black hole masses so far found are close to but below the limit. the eddington luminosity ≃6.5 × 1048 erg s-1 corresponding to mmax is remarkably close to the largest agn bolometric luminosity so far observed. the mass and luminosity limits both rely on a reasonable but currently untestable hypothesis about agn disc formation, so future observations of extreme supermassive black hole masses can therefore probe fundamental disc physics. black holes can in principle grow their masses above mmax by non-luminous means such as mergers with other holes, but cannot become luminous accretors again. they might nevertheless be detectable in other ways, for example through gravitational lensing. i show further that black holes with masses ∼mmax can probably grow above the values specified by the black-hole-host-galaxy scaling relations, in agreement with observation. | how big can a black hole grow? |
energetic gas outflows driven by active galactic nuclei (agns) are considered as one of the mechanisms by which supermassive black holes affect their host galaxies. to probe the impact of agn-driven outflows, it is essential to quantify the size of the region under the influence of such outflows. in the third of a series of papers, we present the spatially resolved kinematics of ionized gas for three additional type 2 agns based on gemini multi-object spectrograph (gmos) integral field spectroscopy. along with the six agns presented in our previous works and the 14 agns with available gmos-integral field unit data, we construct a sample of 23 luminous type 2 agns at z < 0.2, and kinematically measure the size of ionized gas outflows by tracing the radial decrease of the velocity dispersion of the [o iii] λ5007 emission line. the kinematically measured outflow size ranges from 0.60 to ∼7.45 kpc, depending on agn luminosity. we find that the size of the photoionized region is larger than the kinematically measured outflow size, while the flux-weighted photoionization size is significantly smaller. thus, using photoionization size as a proxy for outflow size leads to overestimation or underestimation, and introduces large uncertainties of the mass outflow rate and the energy output rate. we report an outflow size-luminosity relation with a slope of 0.28 ± 0.03, which is shallower than the slope of the correlation between the photoionization size and luminosity. | unraveling the complex structure of agn-driven outflows. iii. the outflow size-luminosity relation |
we present a catalog of 349 giant radio sources (grss including both galaxies and quasars). the database contains all giants known to date from the literature. these grss cover the redshift range of 0.016 < z < 3.22 and include radio sources of projected linear sizes larger than 0.7 mpc, which extend up to 4.7 mpc. we provide the principal parameters (i.e., exact position of the host in the sky, redshift, angular and projected linear size, red optical magnitude, radio morphology type, total radio flux density, and luminosity) for all the sources, as well as characteristics of the sample. based on the distribution of grss in the sky, we identify regions where there is a paucity of giants, so that future surveys for this type of objects could concentrate primarily in these fields. from the analysis presented here, we estimate a lower limit for the expected number of grss as about 2000, for the resolution and sensitivity limits of first, nrao vla sky survey and sloan digital sky survey surveys. compared with earlier compilations, there is a significant increase in the number of large giants with sizes >2 mpc, as well as those at high redshifts with z > 1. we discuss aspects of their evolution and suggest that these are consistent with evolutionary models. | an updated catalog of giant radio sources |
we present the x-ray analysis of 30 luminous quasars at z ≃ 3.0 - 3.3 with pointed xmm-newton observations (28-48 ks) originally obtained by our group to test the suitability of active galactic nuclei as standard candles for cosmological studies. the sample was selected in the optical from the sloan digital sky survey data release 7 to be representative of the most luminous, intrinsically blue quasar population, and by construction boasts a high degree of homogeneity in terms of optical and uv properties. in the x-rays, only four sources are too faint for a detailed spectral analysis, one of which is formally undetected. neglecting one more object later found to be radio-loud, the other 25 quasars are, as a whole, the most x-ray luminous ever observed, with rest-frame 2-10 kev luminosities of 0.5 - 7 × 1045 erg s-1. the continuum photon index distribution, centred at γ ∼ 1.85, is in excellent agreement with those in place at lower redshift, luminosity, and black-hole mass, confirming the universal nature of the x-ray emission mechanism in quasars. even so, when compared against the well-known lx-luv correlation, our quasars show an unexpectedly varied behaviour, splitting into two distinct subsets. about two-thirds of the sources are clustered around the relation with a minimal scatter of 0.1 dex, while the remaining one-third appear to be x-ray underluminous by factors of > 3-10. such a large incidence (≈25%) of x-ray weakness has never been reported in radio-quiet, non-broad absorption line (bal) quasar samples. several factors could contribute to enhancing the x-ray weakness fraction among our z ≃ 3 blue quasars, including variability, mild x-ray obscuration, contamination from weak-line quasars, and missed bals. however, the x-ray weak objects also have, on average, flatter spectra, with no clear evidence of absorption. indeed, column densities in excess of a few ×1022 cm-2 can be ruled out for most of the sample. we suggest that, at least in some of our x-ray weak quasars, the corona might experience a radiatively inefficient phase due to the presence of a powerful accretion-disc wind, which substantially reduces the accretion rate through the inner disc and therefore also the availability of seed photons for compton up-scattering. the origin of the deviations from the lx-luv relation will be further investigated in a series of future studies. | the most luminous blue quasars at 3.0 < z < 3.3. i. a tale of two x-ray populations |
the properties of the molecular gas can shed light on the physical conditions of quasar host galaxies and the effect of feedback from accreting supermassive black holes. we present a new co(2-1) survey of 23 z<0.1 palomar-green quasars conducted with the atacama large millimeter/submillimeter array. co emission was successfully detected in 91% (21/23) of the objects, from which we derive co luminosities, molecular gas masses, and velocity line widths. together with co(1-0) measurements in the literature for 32 quasars (detection rate 53%), there are 15 quasars with both co(1-0) and co(2-1) measurements and, in total, 40 sources with co measurements. we find that the line ratio of r_{21}≡ l_{co}(2-1)^{'}/l_{co(1-0)}^{'} is subthermal and broadly consistent with nearby galaxies and other quasars previously studied. no clear correlation is found between r21 and the intensity of the interstellar radiation field or the luminosity of the active nucleus. as with the general galaxy population, quasar host galaxies exhibit a strong, tight, and linear lir-l_{co}(1-0)^{'} relation, with a normalization consistent with that of starburst systems. we investigate the molecular-to-total-gas mass fraction with the aid of total gas masses inferred from dust masses previously derived from infrared observations. although the scatter is considerable, the current data do not suggest that the co-to-h2 conversion factor of quasar host galaxies significantly differs from that of normal star-forming galaxies. | an alma co(2-1) survey of nearby palomar-green quasars |
a phase of strong interacting matter with deconfined quarks is expected in the core of massive neutron stars. we investigate the quark deconfinement phase transition in cold (t=0 and hot β -stable hadronic matter. assuming a first order phase transition, we calculate and compare the nucleation rate and the nucleation time due to quantum and thermal nucleation mechanisms. we show that above a threshold value of the central pressure a pure hadronic star (hs) (i.e. a compact star with no fraction of deconfined quark matter) is metastable to the conversion to a quark star (qs) (i.e. a hybrid star or a strange star). this process liberates an enormous amount of energy, of the order of 1053erg, which causes a powerful neutrino burst, likely accompanied by intense gravitational waves emission, and possibly by a second delayed (with respect to the supernova explosion forming the hs) explosion which could be the energy source of a powerful gamma-ray burst (grb). this stellar conversion process populates the qs branch of compact stars, thus one has in the universe two coexisting families of compact stars: pure hadronic stars and quark stars. we introduce the concept of critical mass m_{cr} for cold hss and proto-hadronic stars (phss), and the concept of limiting conversion temperature for phss. we show that phss with a mass m < m_{cr} could survive the early stages of their evolution without decaying to qss. finally, we discuss the possible evolutionary paths of proto-hadronic stars. | quark matter nucleation in neutron stars and astrophysical implications |
we present a detailed analysis of an h2-rich, extremely strong intervening damped ly α absorption system (dla) at zabs = 2.786 towards the quasar j 0843+0221, observed with the ultraviolet and visual echelle spectrograph on the very large telescope. the total column density of molecular (resp. atomic) hydrogen is log n(h2) = 21.21 ± 0.02 (resp. log n(h i) = 21.82 ± 0.11), making it to be the first case in quasar absorption line studies with h2 column density as high as what is seen in 13co-selected clouds in the milky way. we find that this system has one of the lowest metallicity detected among h2-bearing dlas, with [zn/h] = -1.52^{+0.08}_{-0.10}. this can be the reason for the marked differences compared to systems with similar h2 column densities in the local universe: (i) the kinetic temperature, t ∼ 120 k, derived from the j = 0, 1 h2 rotational levels is at least twice higher than expected; (ii) there is little dust extinction with av < 0.1; (iii) no co molecules are detected, putting a constraint on the xco factor xco > 2 × 1023 cm-2/(km s-1 k), in the very low metallicity gas. low co and high h2 contents indicate that this system represents 'co-dark/faint' gas. we investigate the physical conditions in the h2-bearing gas using the fine-structure levels of c i, c ii, si ii and the rotational levels of hd and h2. we find the number density to be about n ∼ 260-380 cm-3, implying a high thermal pressure of 3-5 × 104 cm-3 k. we further identify a trend of increasing pressure with increasing total hydrogen column density. this independently supports the suggestion that extremely strong dlas (with log n(h) ∼22) probe high-z galaxies at low impact parameters. | co-dark molecular gas at high redshift: very large h2 content and high pressure in a low-metallicity damped lyman alpha system |
broad emission lines in quasars enable us to "resolve" structure and kinematics of the broad-line emitting region (blr) thought to involve an accretion disk feeding a supermassive black hole. interpretation of broad line measures within the 4de1 formalism simplifies the apparent confusion among such data by contrasting and unifying properties of so-called high and low accreting population a and b sources. hβ serves as an estimator of black hole mass, eddington ratio and source rest frame; the latter being a valuable input for civλ1549 studies which allow us to isolate the blueshifted wind component. optical and hst-uv spectra yield hβ and civλ1549 spectra for low-luminosity sources while vlt-isaac and fors and tng-lrs provide spectra for high-luminosity sources. new high-s/n data for civ in high-luminosity quasars are presented here for comparison with the other previously published data. comparison of hβ and civλ1549 profile widths/shifts indicates that much of the emission from the two lines arise in regions with different structure and kinematics. covering a wide range of luminosity and redshift shows evidence for a correlation between civλ1549 blueshift and source eddington ratio, with a weaker trend with source luminosity (similar amplitude outflows are seen over four of the five dex luminosity ranges in our combined samples). at low luminosity (z ≲ 0.7) only population a sources show evidence for a significant outflow while at high luminosity the outflow signature begins to appear in population b quasars as well. based on observations made with eso telescopes at the la silla paranal observatory under programme id082.b-0572(a) and with the italian telescopio nazionale galileo (tng) operated by the fundación galileo galilei (inaf) at the observatorio del roque de los muchachos.the reduced spectra 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/608/a122 | what does civλ1549 tell us about the physical driver of the eigenvector quasar sequence? |
the thermal state of the post-reionization igm is sensitive to the timing of reionization and the nature of the ionizing sources. we have modelled here the thermal state of the igm in cosmological radiative transfer simulations of a realistic, extended, spatially inhomogeneous hydrogen reionization process, carefully calibrated with ly α forest data. we compare these with cosmological simulations run using a spatially homogeneous ionizing background. the simulations with a realistic growth of ionized regions and a realistic spread in reionization redshifts show, as expected, significant spatial fluctuations in the temperature-density relation (tdr) of the post-reionization igm. the most recently ionized regions are hottest and exhibit a flatter tdr. in simulations consistent with the average tdr inferred from ly α forest data, these spatial fluctuations have a moderate but noticeable effect on the statistical properties of the ly α opacity of the igm at z ∼ 4-6. this should be taken into account in accurate measurements of the thermal properties of the igm and the free-streaming of dark matter from ly α forest data in this redshift range. the spatial variations of the tdr predicted by our simulations are, however, smaller by about a factor of 2 than would be necessary to explain the observed large spatial opacity fluctuations on large (≥50 h-1 comoving mpc) scales atz ≳ 5.5. | spatial fluctuations of the intergalactic temperature-density relation after hydrogen reionization |
this is the second paper in a series on a new luminous z ∼ 5 quasar survey using optical and near-infrared colors. here we present a new determination of the bright end of the quasar luminosity function (qlf) at z ∼ 5. combining our 45 new quasars with previously known quasars that satisfy our selections, we construct the largest uniform luminous z ∼ 5 quasar sample to date, with 99 quasars in the range of 4.7 ≤ z < 5.4 and -29 < m 1450 ≤ -26.8, within the sloan digital sky survey (sdss) footprint. we use a modified 1/v a method including flux limit correction to derive a binned qlf, and we model the parametric qlf using maximum likelihood estimation. with the faint-end slope of the qlf fixed as α = -2.03 from previous deeper samples, the best fit of our qlf gives a flatter bright end slope β = -3.58 ± 0.24 and a fainter break magnitude {m}1450*= -26.98 ± 0.23 than previous studies at similar redshift. combined with previous work at lower and higher redshifts, our result is consistent with a luminosity evolution and density evolution model. using the best-fit qlf, the contribution of quasars to the ionizing background at z ∼ 5 is found to be 18%-45% with a clumping factor c of 2-5. our sample suggests an evolution of radio loud fraction with optical luminosity but no obvious evolution with redshift. | a survey of luminous high-redshift quasars with sdss and wise. ii. the bright end of the quasar luminosity function at z ≈ 5 |
the cosmic x-ray background (cxb) is the total emission from past accretion activity on to supermassive black holes in active galactic nuclei (agn) and peaks in the hard x-ray band (30 kev). in this paper, we identify a significant selection effect operating on the cxb and flux-limited agn surveys, and outline how they must depend heavily on the spin distribution of black holes. we show that, due to the higher radiative efficiency of rapidly spinning black holes, they will be over-represented in the x-ray background, and therefore could be a dominant contributor to the cxb. using a simple bimodal spin distribution, we demonstrate that only 15 per cent maximally spinning agn can produce 50 per cent of the cxb. we also illustrate that invoking a small population of maximally spinning black holes in cxb synthesis models can reproduce the cxb peak without requiring large numbers of compton-thick agn. the spin bias is even more pronounced for flux-limited surveys: 7 per cent of sources with maximally spinning black holes can produce half of the source counts. the detectability for maximum spin black holes can be further boosted in hard (>10 kev) x-rays by up to ∼60 per cent due to pronounced ionized reflection, reducing the percentage of maximally spinning black holes required to produce half of the cxb or survey number counts further. a host of observations are consistent with an over-representation of high-spin black holes. future nustar and astro-h hard x-ray surveys will provide the best constraints on the role of spin within the agn population. | a selection effect boosting the contribution from rapidly spinning black holes to the cosmic x-ray background |
we analyze extensive spectroscopic and photometric data of the hypervariable quasar sdss j141324+530527 (rmid 017) at z = 0.456, an optical “changing-look” quasar from the sloan digital sky survey reverberation mapping project that increased in optical luminosity by a factor ≃10 between 2014 and 2017. the observed broad emission lines all respond in luminosity and width to the changing optical continuum, as expected for photoionization in a stratified, virialized broad emission line region. the luminosity changes therefore result from intrinsic changes in accretion power rather than variable obscuration. the variability is continuous and apparently stochastic, disfavoring an origin as a discrete event such as a tidal disruption flare or microlensing event. it is coordinated on day timescales with blue leading red, consistent with reprocessing powering the entire optical spectral energy distribution. we show that this process cannot work in a standard thin disk geometry on energetic grounds, and would instead require a large covering factor reprocessor. disk instability models could potentially also explain the data, provided that the instability sets in near the inner radius of a geometrically thick accretion disk. | the sloan digital sky survey reverberation mapping project: accretion and broad emission line physics from a hypervariable quasar |
flux-ratio anomalies in quasar lenses can be attributed to dark matter substructure surrounding the lensing galaxy and thus used to constrain the substructure mass fraction. previous applications of this approach infer a substructure abundance that is potentially in tension with the predictions of λ cold dark matter cosmology. however, the assumption that all flux-ratio anomalies are due to substructure is a strong one and alternative explanations have not been fully investigated. here, we use new high-resolution near-ir keck ii adaptive optics imaging for the lens system class b0712+472 to perform pixel-based lens modelling for this system and, in combination with the new very long baseline array radio observations, show that the inclusion of the disc in the lens model can explain the flux-ratio anomalies without the need for dark matter substructures. the projected disc mass comprises 16 per cent of the total lensing mass within the einstein radius and the total disc mass is 1.79 × 1010 m⊙. the case of b0712+472 adds to the evidence that not all flux-ratio anomalies are due to dark subhaloes and highlights the importance of taking the effects of baryonic structures more fully into account in order to obtain an accurate measure of the substructure mass fraction. | sharp - iv. an apparent flux-ratio anomaly resolved by the edge-on disc in b0712+472 |
the radio-loud/radio-quiet (rl/rq) dichotomy in quasars is still an open question. although it is thought that accretion onto supermassive black holes in the centre the host galaxies of quasars is responsible for some radio continuum emission, there is still a debate as to whether star formation or active galactic nuclei (agn) activity dominate the radio continuum luminosity. to date, radio emission in quasars has been investigated almost exclusively using high-frequency observations in which the doppler boosting might have an important effect on the measured radio luminosity, whereas extended structures, best observed at low radio frequencies, are not affected by the doppler enhancement. we used a sample of quasars selected by their optical spectra in conjunction with sensitive and high-resolution low-frequency radio data provided by the low frequency array (lofar) as part of the lofar two-metre sky survey (lotss) to investigate their radio properties using the radio loudness parameter (r =l144 mhz/li band). the examination of the radio continuum emission and rl/rq dichotomy in quasars exhibits that quasars show a wide continuum of radio properties (i.e. no clear bimodality in the distribution of ℛ). radio continuum emission at low frequencies in low-luminosity quasars is consistent with being dominated by star formation. we see a significant albeit weak dependency of ℛ on the source nuclear parameters. for the first time, we are able to resolve radio morphologies of a considerable number of quasars. all these crucial results highlight the impact of the deep and high-resolution low-frequency radio surveys that foreshadow the compelling science cases for the square kilometre array (ska). the catalogue 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/qcat?j/a+a/622/a11 | lotss/hetdex: optical quasars. i. low-frequency radio properties of optically selected quasars |
we present bayesian active galactic nucleus (agn) decomposition analysis for sloan digital sky survey (sdss) spectra, an open source spectral analysis code designed for automatic detailed deconvolution of agn and host galaxy spectra, implemented in python, and designed for the next generation of large-scale surveys. the code simultaneously fits all spectral components, including power-law continuum, stellar line-of-sight velocity distribution, fe ii emission, as well as forbidden (narrow), permitted (broad), and outflow emission line features, all performed using markov chain monte carlo to obtain robust uncertainties and autocorrelation analysis to assess parameter convergence. our code also utilizes multiprocessing for batch fitting large samples of spectra while efficiently managing memory and computation resources and is currently being used in a cluster environment to fit thousands of sdss spectra. we use our code to perform a correlation analysis of 63 sdss type 1 agns with evidence of strong non-gravitational outflow kinematics in the [o iii] λ5007 emission feature. we confirm findings from previous studies that show the core of the [o iii] profile is a suitable surrogate for stellar velocity dispersion σ*, however there is evidence that the core experiences broadening that scales with outflow velocity. we find sufficient evidence that σ*, [o iii] core dispersion, and the non-gravitational outflow dispersion of the [o iii] profile form a plane whose fit results in a scatter of ~0.1 dex. finally, we discuss the implications, caveats, and recommendations when using the [o iii] dispersion as a surrogate for σ* for the mbh-σ* relation. | bayesian agn decomposition analysis for sdss spectra: a correlation analysis of [o iii] λ5007 outflow kinematics with agn and host galaxy properties |
we examine the impact of black hole jet feedback on the properties of the low-redshift intergalactic medium (igm) in the simba simulation, with a focus on the lyα forest mean flux decrement da. without jet feedback, we confirm the photon underproduction crisis (puc) in which γh i at $z$ = 0 must be increased by 6 times over the haardt & madau value in order to match the observed da. turning on jet feedback lowers this discrepancy to ∼2.5 times, and additionally using the recent faucher-giguère background mostly resolves the puc, along with producing a flux probability distribution function in accord with observations. the puc becomes apparent at late epochs ( $z \lesssim 1$ ) where the jet and no-jet simulations diverge; at higher redshifts simba reproduces the observed da with no adjustment, with or without jets. the main impact of jet feedback is to lower the cosmic baryon fraction in the diffuse igm from 39 per cent to 16 per cent at $z$ = 0, while increasing the warm-hot intergalactic medium (whim) baryon fraction from 30 per cent to 70 per cent; the lowering of the diffuse igm content directly translates into a lowering of da by a similar factor. comparing to the older mufasa simulation that employs different quenching feedback but is otherwise similar to simba, mufasa matches da less well than simba, suggesting that low-redshift measurements of da and γh i could provide constraints on feedback mechanisms. our results suggest that widespread igm heating at late times is a plausible solution to the puc, and that simba's jet active galactic nucleus feedback model, included to quench massive galaxies, approximately yields this required heating. | jet feedback and the photon underproduction crisis in simba |
time delay cosmography uses the arrival time delays between images in strong gravitational lenses to measure cosmological parameters, in particular the hubble constant h0. the lens models used in time delay cosmography omit dark matter subhalos and line-of-sight halos because their effects are assumed to be negligible. we explicitly quantify this assumption by analyzing mock lens systems that include full populations of dark matter subhalos and line-of-sight halos, applying the same modeling assumptions used in the literature to infer h0. we base the mock lenses on six quadruply imaged quasars that have delivered measurements of the hubble constant, and quantify the additional uncertainties and/or bias on a lens-by-lens basis. we show that omitting dark substructure does not bias inferences of h0. however, perturbations from substructure contribute an additional source of random uncertainty in the inferred value of h0 that scales as the square root of the lensing volume divided by the longest time delay. this additional source of uncertainty, for which we provide a fitting function, ranges from 0.7 - 2.4%. it may need to be incorporated in the error budget as the precision of cosmographic inferences from single lenses improves, and it sets a precision limit on inferences from single lenses. | tdcosmo. iii. dark matter substructure meets dark energy. the effects of (sub)halos on strong-lensing measurements of h0 |
the early evolution of the quasar luminosity function (qlf) and black hole mass function (bhmf) encodes key information on the physics determining the radiative and accretion processes of supermassive black holes (bhs) in high-z quasars. although the qlf shape has been constrained by recent observations, it remains challenging to develop a theoretical model that explains its redshift evolution associated with bh growth self-consistently. in this study, based on a semianalytical model for the bh formation and growth, we construct the qlf and bhmf of the early bh population that experiences multiple accretion bursts, in each of which a constant eddington ratio is assigned following a schechter distribution function. our best-fit model to reproduce the observed qlf and bhmf at z ≃ 6 suggests that several episodes of moderate super-eddington accretion occur and each of them lasts for τ ≃ 20-30 myr. the average duty cycle in super-eddington phases is ≃15% for massive bhs that reach ≳108 m ⊙ by z ≃ 6, which is nearly twice that of the entire population. we find that the observed eddington ratio distribution function is skewed to a lognormal shape owing to detection limits of quasar surveys. the predicted redshift evolution of the qlf and bhmf suggests a rapid decay of their number and mass density in a cosmic volume toward z ≳ 6. these results will be unveiled by future deep and wide surveys with the james webb space telescope, roman space telescope, and euclid. | the assembly of black hole mass and luminosity functions of high-redshift quasars via multiple accretion episodes |
modeling the 21-cm global signal from the cosmic dawn is challenging due to the many poorly constrained physical processes that come into play. we address this problem using the semi-analytical code 'cosmic archaeology tool' (cat). cat follows the evolution of dark matter haloes tracking their merger history and provides an ab initio description of their baryonic evolution, starting from the formation of the first (pop iii) stars and black holes (bhs) in mini-haloes at z > 20. the model is anchored to observations of galaxies and agn at z < 6 and predicts a reionization history consistent with constraints. in this work, we compute the evolution of the mean global 21-cm signal between 4 ≤ z ≤ 40 based on the rate of formation and emission properties of stars and accreting bhs. we obtain an absorption profile with a maximum depth δtb = -95 mk at z ~ 26.5 (54 mhz). this feature is quickly suppressed turning into an emission signal at z = 20 due to the contribution of accreting bhs that efficiently heat the intergalactic medium (igm) at z < 27. the high-z absorption feature is caused by the early coupling between the spin and kinetic temperature of the igm induced by pop iii star formation episodes in mini-haloes. once we account for an additional radio background from early bhs, we are able to reproduce the timing and the depth of the edges signal only if we consider a smaller x-ray background from accreting bhs, but not the shape. | the role of pop iii stars and early black holes in the 21-cm signal from cosmic dawn |
until recently, relativistic jets were ubiquitously found to be launched from giant elliptical galaxies. however, the detection by the fermi-lat of γ-ray emission from radio-loud narrow-line seyfert 1 (rl-nlsy1) galaxies raised doubts on this relation. here, we morphologically characterize a sample of 29 rl-nlsy1s (including 12 γ-emitters, γ-nlsy1s) in order to find clues on the conditions needed by active galactic nuclei (agns) to produce relativistic jets. we use deep near-infrared images from the nordic optical telescope and the eso vlt to analyse the surface brightness distribution of the galaxies in the sample. we detected 72 per cent of the hosts (24 per cent classified as γ-nlsy1s). although we cannot rule out that some rl-nlsy1s are hosted by dispersion-supported systems, our findings strongly indicate that rl-nlsy1 hosts are preferentially disc galaxies. 52 per cent of the resolved hosts (77 per cent non-γ-emitters and 20 per cent γ-emitters) show bars with morphological properties (long and weak) consistent with models that promote gas inflows, which might trigger nuclear activity. the extremely red bulges of the γ-nlsy1s, and features that suggest minor mergers in 75 per cent of their hosts, might hint to the necessary conditions for γ-rays to be produced. among the features that suggest mergers in our sample, we find six galaxies that show offset stellar bulges with respect to their agns. when we plot the nuclear versus the bulge magnitude, rl-nlsy1s locate in the low-luminosity end of flat spectrum radio quasars, suggesting a similar accretion mode between these two agn types. | the disc-like host galaxies of radio-loud narrow-line seyfert 1s |
we study the effect of radio-jet core shift, which is a dependence of the position of the jet radio core on the observational frequency. we derive a new method of measuring the jet magnetic field based on both the value of the shift and the observed radio flux, which complements the standard method that assumes equipartition. using both methods, we re-analyse the blazar sample of zamaninasab et al. we find that equipartition is satisfied only if the jet opening angle in the radio core region is close to the values found observationally, ≃0.1-0.2 divided by the bulk lorentz factor, γj. larger values, e.g. 1/γj, would imply magnetic fields much above equipartition. a small jet opening angle implies in turn the magnetization parameter of ≪1. we determine the jet magnetic flux taking into account this effect. we find that the transverse-averaged jet magnetic flux is fully compatible with the model of jet formation due to black hole (bh) spin-energy extraction and the accretion being a magnetically arrested disc (mad). we calculate the jet average mass-flow rate corresponding to this model and find it consists of a substantial fraction of the mass accretion rate. this suggests the jet composition with a large fraction of baryons. we also calculate the average jet power, and find it moderately exceeds the accretion power, dot{m} c^2, reflecting bh spin energy extraction. we find our results for radio galaxies at low eddington ratios are compatible with mads but require a low radiative efficiency, as predicted by standard accretion models. | core shifts, magnetic fields and magnetization of extragalactic jets |
the observed large-scale scatter in lyα opacity of the intergalactic medium at z < 6 implies large fluctuations in the neutral hydrogen fraction that are unexpected long after reionization has ended. a number of models have emerged to explain these fluctuations that make testable predictions for the relationship between lyα opacity and density. we present selections of z = 5.7 lyα-emitting galaxies (laes) in the fields surrounding two highly opaque quasar sightlines with long lyα troughs. the fields lie toward the z = 6.0 quasar ulas j0148+0600, for which we reanalyze previously published results using improved photometric selection, and toward the z = 6.15 quasar sdss j1250+3130, for which results are presented here for the first time. in both fields, we report a deficit of laes within 20 h -1 mpc of the quasar. the association of highly opaque sightlines with galaxy underdensities in these two fields is consistent with models in which the scatter in lyα opacity is driven by large-scale fluctuations in the ionizing uv background or by an ultra-late reionization that has not yet concluded at z = 5.7. | constraints on the end of reionization from the density fields surrounding two highly opaque quasar sightlines |
context. investigation of the hard x-ray emission properties of blazars is key to the understanding of the central engine of the sources and associated jet process. in particular, simultaneous spectral and timing analyses of the intraday hard x-ray observations provide us a means to peer into the compact innermost blazar regions that are not accessible to our current instruments.aims: the primary objective of the work is to associate the observed hard x-ray variability properties in blazars with their flux and spectral states, thereby, based on the correlation among these states, extract the details about the emission regions and processes occurring near the central engine.methods: we carried out timing, spectral, and cross-correlation analysis of 31 nustar observations of 13 blazars. we investigated the spectral shapes of the sources using single power-law, broken power-law, and log-parabola models. we also studied the co-relation between the soft and hard emission using z-transformed discrete correlation function. in addition, we attempted to constrain the smallest emission regions using minimum variability timescales derived from the light curves.results: we found that, for most of the sources, the hard x-ray emission can be well represented by the log-parabola model and that the spectral slopes for different blazar subclasses are consistent with the so-called blazar sequence. we also report the steepest spectra (γ ∼ 3) in the bl lacertae pks 2155-304 and the hardest spectra (γ ∼ 1.4) in the flat-spectrum radio quasar pks 2149-306. in addition, we noted a close connection between the flux and spectral slope within the source subclass in the sense that high flux and/or flux states tend to be harder in spectra. in bl lacertae objects, assuming particle acceleration by diffusive shocks and synchrotron cooling as the dominant processes governing the observed flux variability, we constrain the magnetic field of the emission region to be a few gauss; whereas in flat-spectrum radio quasars, using external compton models, we estimate the energy of the lower end of the injected electrons to be a few lorentz factors. | hard x-ray properties of nustar blazars |
we perform a measurement of the hubble constant, h 0, using the latest baryonic acoustic oscillation (bao) measurements from galaxy surveys of 6dfgs, sdss dr7 main galaxy sample, boss dr12 sample, and eboss dr14 quasar sample, in the framework of a flat λcdm model. based on the kullback-leibler divergence, we examine the consistency of h 0 values derived from various data sets. we find that our measurement is consistent with that derived from planck and with the local measurement of h 0 using the cepheids and type ia supernovae. we perform forecasts on h 0 from future bao measurements, and find that the uncertainty of h 0 determined by future bao data alone, including complete eboss, desi, and euclid-like, is comparable with that from local measurements. | a measurement of the hubble constant using galaxy redshift surveys |
we extract observational constraints on f(t) gravity, using the recently proposed statistical method which is not affected by the value of h0 and thus it bypasses the problem of the disagreement in its exact numerical value between planck and direct measurements. we use direct measurements of the hubble parameter with the corresponding covariance matrix, and for completeness we perform a joint analysis using the latest data from supernovae type ia based on jla sample, quasi-stellar objects, and cosmic microwave background shift parameter from planck. we analyze a large family of f(t) models, and we compare the fitting results with λcdm cosmology using the aic statistical test. utilizing only the hubble parameter data we find that in the case of the power-law f(t) model a small but non-zero deviation from λcdm cosmology is slightly favored at 1-σ, nevertheless the corresponding aic value shows a statistical equivalence with it. finally, the join analysis reveals that all f(t) models are very efficient and in very good agreement with observations. | updated constraints on f(t) models using direct and indirect measurements of the hubble parameter |
past x-ray observations of the nearby luminous quasar pds 456 (at z = 0.184) have revealed a wide angle accretion disk wind, with an outflow velocity of ∼-0.25c. here, we unveil a new, relativistic component of the wind through hard x-ray observations with nustar and xmm-newton, obtained in 2017 march when the quasar was in a low-flux state. this very fast wind component, with an outflow velocity of -0.46 ± 0.02c, is detected in the iron k band, in addition to the -0.25c wind zone. the relativistic component may arise from the innermost disk wind, launched from close to the black hole at a radius of ∼10 gravitational radii. the opacity of the fast wind also increases during a possible obscuration event lasting for 50 ks. we suggest that the very fast wind may only be apparent during the lowest x-ray flux states of pds 456, becoming overly ionized as the luminosity increases. overall, the total wind power may even approach the eddington value. | a new relativistic component of the accretion disk wind in pds 456 |
according to the unified model of active galactic nuclei (agns), a putative dusty torus plays an important role in determining an agn’s external appearance. however, information on the physical properties of the torus is very scarce. we perform detailed decomposition of the infrared (1-500 μm) spectral energy distribution of 76 z < 0.5 palomar-green quasars, combining photometric data from the two micron all-sky survey, wide-field infrared survey explorer, and herschel with spitzer spectroscopy. our fits favor recent torus spectral models that properly treat the different sublimation temperatures of silicates and graphite and consider a polar wind component. the agn-heated dust emission from the torus contributes a significant fraction (∼70%) of the total infrared (1-1000 μm) luminosity. the torus luminosity correlates well with the strength of the ultraviolet/optical continuum and the broad hβ emission line, indicating a close link between the central ionization source and re-radiation by the torus. consistent with the unified model, most quasars have tori that are only mildly inclined along the line of sight. the half-opening angle of the torus, a measure of its covering factor, declines with increasing accretion rate until the eddington ratio reaches ∼0.5, above which the trend reverses. this behavior likely results from the change of the geometry of the accretion flow, from a standard geometrically thin disk at moderate accretion rates, to a slim disk at high accretion rates. | the infrared emission and opening angle of the torus in quasars |
by comparing mg ii absorption in the circumgalactic medium (cgm) of group environments to isolated galaxies, we investigated the impact of environment on the cgm. an mg ii absorber is associated with a group if there are two or more galaxies at the absorption redshift within a projected distance of d = 200 kpc from a background quasar and a line-of-sight velocity separation of 500 km s-1. we compiled a sample of 29 group environments consisting of 74 galaxies (two to five galaxies per group) at 0.113< {z}gal}< 0.888. the group absorber median equivalent width (< {w}r(2796)> =0.65+/- 0.13 å) and covering fraction ({f}c={0.89}-0.09+0.05) are larger than isolated absorbers (1.27σ and 2.2σ, respectively), but median column densities are statistically consistent. a pixel-velocity two-point correlation function analysis shows that group environment kinematics are statistically comparable to isolated environments (0.8σ), but with more power for high velocity dispersions similar to outflow kinematics. group absorbers display more optical depth at larger velocities. a superposition model in which multiple galaxies contribute to the observed gas matches larger equivalent width group absorbers but significantly overpredicts the kinematics owing to large velocity separations between member galaxies. finally, galaxy-galaxy groups (similar member galaxy luminosities) may have larger absorber median equivalent widths (1.7σ) and velocity dispersions (2.5σ) than galaxy-dwarf groups (disparate luminosities). we suggest that the observed gas is coupled to the group rather than individual galaxies, forming an intragroup medium. gas may be deposited into this medium by multiple galaxies via outflowing winds undergoing an intergalactic transfer between member galaxies or from tidal stripping of interacting members. | magiicat vi. the mg ii intragroup medium is kinematically complex |
we investigate quasar outflows at z ≥ 6 by performing zoom-in cosmological hydrodynamical simulations. by employing the smoothed particle hydrodynamics code gadget-3, we zoom in the 2r200 region around a 2 × 1012 m⊙ halo at z = 6, inside a (500 mpc)3 comoving volume. we compare the results of our active galactic nuclei (agn) runs with a control simulation in which only stellar/sn feedback is considered. seeding 105 m⊙ black holes (bhs) at the centres of 109 m⊙ haloes, we find the following results. bhs accrete gas at the eddington rate over z = 9-6. at z = 6, our most-massive bh has grown to mbh = 4 × 109 m⊙. fast (vr > 1000 km s-1), powerful (\dot{m}_out ∼ 2000 m_{⊙} yr-1) outflows of shock-heated low-density gas form at z ∼ 7, and propagate up to hundreds kpc. star formation is quenched over z = 8-6, and the total star formation rate (sfr surface density near the galaxy centre) is reduced by a factor of 5 (1000). we analyse the relative contribution of multiple physical process: (i) disrupting cosmic filamentary cold gas inflows, (ii) reducing central gas density, (iii) ejecting gas outside the galaxy; and find that agn feedback has the following effects at z = 6. the inflowing gas mass fraction is reduced by ∼ 12 per cent, the high-density gas fraction is lowered by ∼ 13 per cent, and ∼ 20 per cent of the gas outflows at a speed larger than the escape velocity (500 km s-1). we conclude that quasar-host galaxies at z ≥ 6 are accreting non-negligible amount of cosmic gas, nevertheless agn feedback quenches their star formation dominantly by powerful outflows ejecting gas out of the host galaxy halo. | quasar outflows at z ≥ 6: the impact on the host galaxies |
context. obscured active galactic nuclei (agn) represent a significant fraction of the entire agn population, especially at high redshift (∼70% at z = 3 - 5). they are often characterized by the presence of large gas and dust reservoirs that are thought to sustain and possibly obscure vigorous star formation processes that make these objects shine at fir and submillimeter wavelengths. studying the physical properties of obscured agn and their host galaxies is crucial to shedding light on the early stages of a massive system lifetime.aims: we aim to investigate the contribution of the interstellar medium (ism) to the obscuration of quasars in a sample of distant highly star forming galaxies and to unveil their morphological and kinematics properties.methods: we exploit atacama large millimeter/submillimeter array cycle 4 observations of the continuum (∼2.1 mm) and high-j co emission of a sample of six x-ray selected, fir detected galaxies hosting an obscured agn at zspec > 2.5 in the 7 ms chandra deep field-south. we measured the masses and sizes of the dust and molecular gas by fitting the images, visibilities, and spectra, and we derived the gas density and column density on the basis of a uniform sphere geometry. finally, we compared the measured column densities with those derived from the chandra x-ray spectra.results: we detected both the continuum and line emission for three sources for which we measured both the flux density and size. for the undetected sources, we derived an upper limit on the flux density from the root mean square of the images. we found that the detected galaxies are rich in gas and dust (molecular gas mass in the range < 0.5-2.7 × 1010 m⊙ for αco = 0.8 and up to ∼2 × 1011 m⊙ for αco = 6.5, and dust mass < 0.9-4.9 × 108 m⊙) and generally compact (gas major axis 2.1-3.0 kpc, dust major axis 1.4-2.7 kpc). the column densities associated with the ism are on the order of 1023 - 24 cm-2, which is comparable with those derived from the x-ray spectra. for the detected sources we also derived dynamical masses in the range 0.8-3.7 × 1010 m⊙.conclusions: we conclude that the ism of high redshift galaxies can substantially contribute to nuclear obscuration up to the compton-thick (> 1024 cm-2) regime. in addition, we found that all the detected sources show a velocity gradient reminding one rotating system, even though two of them show peculiar features in their morphology that can be associated with a chaotic, possibly merging, structure. the reduced images 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/636/a37 | dust and gas content of high-redshift galaxies hosting obscured agn in the chandra deep field-south |
context. the physics and demographics of high-redshift obscured active galactic nuclei (agn) is still scarcely investigated. new samples of such objects, selected with different techniques, can provide useful insights into their physical properties.aims: with the goal to determine the properties of the gas in the emitting region of type 2 agn, in particular, the gas metal content, we exploit predictions from photoionization models, including new parameterizations for the distance of gas distribution from the central source and internal microturbulence in the emitting clouds, to interpret rest-frame uv spectral data.methods: we selected a sample of 90 obscured (type 2) agn with 1.45 ≤ z ≤ 3.05 from the zcosmos-deep galaxy sample by 5σ detection of the high-ionization c iv λ1549 narrow emission line. this feature in a galaxy spectrum is often associated with nuclear activity, and the selection effectiveness has also been confirmed by diagnostic diagrams based on utraviolet (uv) emission-line ratios. we applied the same selection technique and collected a sample of 102 unobscured (type 1) agn. taking advantage of the large amount of multiband data available in the cosmos field, we investigated the properties of the c iv-selected type 2 agn, focusing on their host galaxies, x-ray emission, and uv emission lines. finally, we investigated the physical properties of the ionized gas in the narrow-line region (nlr) of this type 2 agn sample by combining the analysis of strong uv emission lines with predictions from photoionization models.results: we find that in order to successfully reproduce the relative intensity of uv emission lines of the selected high-z type 2 agn, two new ingredients in the photoionization models are fundamental: small inner radii of the nlr (≈90 pc for lagn = 1045 erg s-1), and the internal dissipative microturbulence of the gas-emitting clouds (with vmicr ≈ 100 km s-1). with these modified models, we compute the gas-phase metallicity of the nlr, and our measurements indicate a statistically significant evolution of the metal content with redshift. finally, we do not observe a strong relationship between the nlr gas metallicity and the stellar mass of the host galaxy in our c iv-selected type 2 agn sample. the type 2 agn catalog 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/qcat?j/a+a/626/a9 | obscured agn at 1.5 < z < 3.0 from the zcosmos-deep survey . i. properties of the emitting gas in the narrow-line region |
we have conducted an optical long-slit spectroscopic survey of 1022 galaxies using the 10 m hobby-eberly telescope (het) at mcdonald observatory. the main goal of the het massive galaxy survey (hetmgs) is to find nearby galaxies that are suitable for black hole mass measurements. in order to measure accurately the black hole mass, one should kinematically resolve the region where the black hole dominates the gravitational potential. for most galaxies, this region is much less than an arcsecond. thus, black hole masses are best measured in nearby galaxies with telescopes that obtain high spatial resolution. the hetmgs focuses on those galaxies predicted to have the largest sphere-of-influence, based on published stellar velocity dispersions or the galaxy fundamental plane. to ensure coverage over galaxy types, the survey targets those galaxies across a face-on projection of the fundamental plane. we present the sample selection and resulting data products from the long-slit observations, including central stellar kinematics and emission line ratios. the full data set, including spectra and resolved kinematics, is available online. additionally, we show that the current crop of black hole masses are highly biased toward dense galaxies and that especially large disks and low dispersion galaxies are under-represented. this survey provides the necessary groundwork for future systematic black hole mass measurement campaigns. | hunting for supermassive black holes in nearby galaxies with the hobby-eberly telescope |
aims: galaxy-scale outflows are currently observed in many active galactic nuclei (agns); however, characterisation of them in terms of their (multi-) phase nature, amount of flowing material, and effects on their host galaxy is still unresolved. in particular, ionised gas mass outflow rate and related energetics are still affected by many sources of uncertainty. in this respect, outflowing gas plasma conditions, being largely unknown, play a crucial role.methods: we have analysed stacked spectra and sub-samples of sources with high signal-to-noise temperature- and density-sensitive emission lines to derive the plasma properties of the outflowing ionised gas component. we did this by taking advantage of the spectroscopic analysis results we obtained while studying the x-ray/sdss sample of 563 agns at z < 0.8 presented in our companion paper. for these sources, we also studied in detail various diagnostic diagrams to infer information about outflowing gas ionisation mechanisms.results: we derive, for the first time, median values for electron temperature and density of outflowing gas from medium-size samples ( 30 targets) and stacked spectra of agns. evidence of shock excitation are found for outflowing gas.conclusions: we measure electron temperatures of the order of 1.7 × 104 k and densities of 1200 cm-3 for faint and moderately luminous agns (intrinsic x-ray luminosity 40.5 < log (lx) < 44 in the 2-10 kev band). we note that the electron density that is usually assumed (ne = 100 cm-3) in ejected material might result in relevant overestimates of flow mass rates and energetics and, as a consequence, of the effects of agn-driven outflows on the host galaxy. | an x-ray/sdss sample. ii. agn-driven outflowing gas plasma properties |
we propose the development of x-ray interferometry (xri), to reveal the universe at high energies with ultra-high spatial resolution. with baselines which can be accommodated on a single spacecraft, xri can reach 100 μ as resolution at 10 å (1.2 kev) and 20 μ as at 2 å (6 kev), enabling imaging and imaging-spectroscopy of (for example) x-ray coronae of nearby accreting supermassive black holes (smbh) and the smbh `shadow'; smbh accretion flows and outflows; x-ray binary winds and orbits; stellar coronae within ∼100 pc and many exoplanets which transit across them. for sufficiently luminous sources xri will resolve sub-pc scales across the entire observable universe, revealing accreting binary smbhs and enabling trigonometric measurements of the hubble constant with x-ray light echoes from quasars or explosive transients. a multi-spacecraft `constellation' interferometer would resolve well below 1 μ as, enabling smbh event horizons to be resolved in many active galaxies and the detailed study of the effects of strong field gravity on the dynamics and emission from accreting gas close to the black hole. | the high energy universe at ultra-high resolution: the power and promise of x-ray interferometry |
accreting supermassive black holes (smbhs), also known as active galactic nuclei (agn), are generally surrounded by large amounts of gas and dust. this surrounding material reprocesses the primary x-ray emission produced close to the smbh and gives rise to several components in the broadband x-ray spectra of agn, including a power-law possibly associated with thomson-scattered radiation. in this work, we study the properties of this scattered component for a sample of 386 hard-x-ray-selected, nearby ($z\sim0.03$) obscured agn from the 70-month swift/bat catalogue. we investigate how the fraction of thomson-scattered radiation correlates with different physical properties of agn, such as line-of-sight column density, x-ray luminosity, black hole mass, and eddington ratio. we find a significant negative correlation between the scattering fraction and the column density. based on a large number of spectral simulations, we exclude the possibility that this anticorrelation is due to degeneracies between the parameters. the negative correlation also persists when considering different ranges of luminosity, black hole mass, and eddington ratio. we discuss how this correlation might be either due to the angle dependence of the thomson cross-section or to more obscured sources having a higher covering factor of the torus. we also find a positive correlation between the scattering fraction and the ratio of [o iii] λ5007 to x-ray luminosity. this result is consistent with previous studies and suggests that the thomson-scattered component is associated with the narrow-line region. | bat agn spectroscopic survey xxvii: scattered x-ray radiation in obscured active galactic nuclei |
faint z ∼ 5 quasars with m1450 ∼ -23 mag are known to be potentially important contributors to the ultraviolet ionizing background in the postreionization era. however, their number density has not been well determined, making it difficult to assess their role in the early ionization of the intergalactic medium (igm). in this work, we present the updated results of our z ∼ 5 quasar survey using the infrared medium-deep survey (ims), a near-infrared imaging survey covering an area of 85 deg2. from our spectroscopic observations with the gemini multi-object spectrograph on the gemini-south 8 m telescope, we discovered eight new quasars at z ∼ 5 with -26.1 ≤ m1450 ≤ -23.3. combining our ims faint quasars (m1450 > -27 mag) with the brighter sloan digital sky survey quasars (m1450 < -27 mag), we derive the z ∼ 5 quasar luminosity function (qlf) without any fixed parameters down to the magnitude limit of m1450 = -23 mag. we find that the faint-end slope of the qlf is very flat ( $\alpha =-{1.2}_{-0.6}^{+1.4}$ ), with a characteristic luminosity of ${m}_{1450}^{* }=-{25.8}_{-1.1}^{+1.4}$ mag. the number density of z ∼ 5 quasars from the qlf gives an ionizing emissivity at 912 å of ɛ912 = (3.7-7.1) × 1023 erg s-1 hz-1 mpc-3 and an ionizing photon density of ${\dot{n}}_{\mathrm{ion}}=(3.0\mbox{--}5.7)\,\times {10}^{49}$ mpc-3 s-1. these results imply that quasars are responsible for only 10%-20% (up to 50% even in the extreme case) of the photons required to completely ionize the igm at z ∼ 5, disfavoring the idea that quasars alone could have ionized the igm at z ∼ 5. | the infrared medium-deep survey. viii. quasar luminosity function at z ∼ 5 |
we devise a method to constrain self-interacting dark matter (sidm) from observations of quadruply imaged quasars, and apply it to five self-interaction potentials with a long-range dark force. we consider several sidm models with an attractive potential that allows for the formation of quasibound states, giving rise to resonant features in the cross section localized at particular velocities below 50 km s−1 . we propose these resonances, which amplify or suppress the cross section amplitude by over an order of magnitude, accelerate or delay the onset of core collapse in low-mass dark matter halos, and derive constraints on the timescale for core collapse for the five interaction potentials we consider. our data strongly disfavors scenarios in which a majority of halos core collapse, with the strongest constraints obtained for cross section strengths exceeding 100 cm2 g−1 at relative velocities below 30 km s−1 . this work opens a new avenue to explore the vast landscape of possible sidm theories. | constraining resonant dark matter self-interactions with strong gravitational lenses |
the 180 day space telescope and optical reverberation mapping campaign on ngc 5548 discovered an anomalous period, the broad-line region (blr) holiday, in which the emission lines decorrelated from the continuum variations. this is important since the correlation between the continuum-flux variations and the emission-line response is the basic assumption for black hole (bh) mass determinations through reverberation mapping. during the blr holiday the high-ionization intrinsic absorption lines also decorrelated from the continuum as a result of the variable covering factor of the line-of-sight (los) obscurer. the emission lines are not confined to the los, so this does not explain the blr holiday. if the los obscurer is a disk wind, its streamlines must extend down to the plane of the disk and the base of the wind would lie between the bh and the blr, forming an equatorial obscurer. this obscurer can be transparent to ionizing radiation, or can be translucent, blocking only parts of the spectral energy distribution, depending on its density. an emission-line holiday is produced if the wind density increases only slightly above its transparent state. both obscurers are parts of the same wind, so they can have associated behavior in a way that explains both holidays. a very dense wind would block nearly all ionizing radiation, producing a seyfert 2 and possibly providing a contributor to the changing-look active galactic nucleus phenomenon. disk winds are very common and we propose that the equatorial obscurers are too, but mostly in a transparent state. | a wind-based unification model for ngc 5548: spectral holidays, nondisk emission, and implications for changing-look quasars |
substantial evidence in the last few decades suggests that outflows from supermassive black holes (smbh) may play a significant role in the evolution of galaxies. these outflows, powered by active galactic nuclei (agn), are thought to be the fundamental mechanism by which the smbh transfers a significant fraction of its accretion energy to the surrounding environment. large-scale outflows known as warm absorbers (wa) and fast disk winds known as ultra-fast outflows (ufo) are commonly found in the spectra of many seyfert galaxies and quasars, and a correlation has been suggested between them. recent detections of low ionization and low column density outflows, but with a high velocity comparable to ufos, challenge such initial possible correlations. observations of ufos in agn indicate that their energetics may be enough to have an impact on the interstellar medium (ism). however, observational evidence of the interaction between the inner high-ionization outflow and the ism is still missing. we present here the spectral analysis of 12 xmm-newton/epic archival observations of the quasar pg 1114+445, aimed at studying the complex outflowing nature of its absorbers. our analysis revealed the presence of three absorbing structures. we find a wa with velocity v ∼ 530 km s-1, ionization log ξ/erg cm s-1 ∼ 0.35, and column density log nh/cm-2 ∼ 22, and a ufo with vout ∼ 0.145c, log ξ/erg cm s-1 ∼ 4, and log nh/cm-2 ∼ 23. we also find an additional absorber in the soft x-rays (e < 2 kev) with velocity comparable to that of the ufo (vout ∼ 0.120c), but ionization (log ξ/erg cm s-1 ∼ 0.5) and column density (log nh/cm-2 ∼ 21.5) comparable with those of the wa. the ionization, velocity, and variability of the three absorbers indicate an origin in a multiphase and multiscale outflow, consistent with entrainment of the clumpy ism by an inner ufo moving at ∼15% the speed of light, producing an entrained ultra-fast outflow (e-ufo). | multiphase quasar-driven outflows in pg 1114+445. i. entrained ultra-fast outflows |
we present an analysis of the proper motion of the andromeda galaxy (m31), based on the early third data release of the gaia mission. we use the gaia photometry to select young blue main-sequence stars and apply several quality cuts to obtain clean samples of these tracers. after correcting the proper motion measurements for the internal rotation of the m31 disc motion, we derive an apparent motion of $52.5 \pm 5.8{\rm \, \mu as\,yr^{-1}}$ with respect to the gaia reference frame, or $61.9 \pm 9.7{\rm \, \mu as\,yr^{-1}}$ after applying a zero-point correction determined from quasars within 20° from m31 and a correction from systemic biases. accounting for the solar reflex motion, we deduce a relative velocity between andromeda and the milky way (in a non-rotating frame at the current location of the sun) of $42.2 \pm 39.3 {\rm \, km\, s^{-1}}$ along right ascension ($40.0 \pm 39.3 {\rm \, km\, s^{-1}}$ along galactic longitude) and $-59.4 \pm 30.3 {\rm \, km\, s^{-1}}$ along declination ($-60.9 \pm 30.3 {\rm \, km\, s^{-1}}$ along galactic latitude), with a total transverse velocity of $v_{\rm trans} = 82.4 \pm 31.2 {\rm \, km\, s^{-1}}$. these values are consistent with (but more accurate than) earlier hubble space telescope measurements that predict a future merger between the two galaxies. we also note a surprisingly large difference in the derived proper motion between the blue stars in m31 and samples of red stars that appear to lie in that galaxy. we propose several hypotheses to explain the discrepancy but found no clear evidence with the current data to privilege any one of them. | the proper motion of andromeda from gaia edr3: confirming a nearly radial orbit |
previous studies of fueling black holes in galactic nuclei have argued (on scales ${\sim}0.01{-}1000\,$pc) accretion is dynamical with inflow rates $\dot{m}\sim \eta \, m_{\rm gas}/t_{\rm dyn}$ in terms of gas mass mgas, dynamical time tdyn, and some η. but these models generally neglected expulsion of gas by stellar feedback, or considered extremely high densities where expulsion is inefficient. studies of star formation, however, have shown on sub-kpc scales the expulsion efficiency fwind = mejected/mtotal scales with the gravitational acceleration as $(1-f_{\rm wind})/f_{\rm wind}\sim \bar{a}_{\rm grav}/\langle \dot{p}/m_{\ast }\rangle \sim \sigma _{\rm eff}/\sigma _{\rm crit}$ where $\bar{a}_{\rm grav}\equiv g\, m_{\rm tot}(\lt r)/r^{2}$ and $\langle \dot{p}/m_{\ast }\rangle$ is the momentum injection rate from young stars. adopting this as the simplest correction for stellar feedback, $\eta \rightarrow \eta \, (1-f_{\rm wind})$, we show this provides a more accurate description of simulations with stellar feedback at low densities. this has immediate consequences, predicting the slope and normalization of the mbh - σ and mbh - mbulge relation, lagn -sfr relations, and explanations for outliers in compact es. most strikingly, because star formation simulations show expulsion is efficient (fwind ~ 1) below total-mass surface density $m_{\rm tot}/\pi \, r^{2}\lt \sigma _{\rm crit}\sim 3\times 10^{9}\, \mathrm{m}_{\odot }\, {\rm kpc^{-2}}$ (where $\sigma _{\rm crit}=\langle \dot{p}/m_{\ast }\rangle /(\pi \, g)$), bh mass is predicted to specifically trace host galaxy properties above a critical surface brightness σcrit (b-band $\mu _{\rm b}^{\rm crit}\sim 19\, {\rm mag\, arcsec^{-2}}$). this naturally explains why bh masses preferentially reflect bulge properties or central surface densities (e.g. $\sigma _{1\, {\rm kpc}}$), not 'total' galaxy properties. | why do black holes trace bulges (& central surface densities), instead of galaxies as a whole? |
large fractions of metals are missing from the observable gas-phase in the interstellar medium (ism) because they are incorporated into dust grains. this phenomenon is called dust depletion. it is important to study the depletion of metals into dust grains in the ism to investigate the origin and evolution of metals and cosmic dust. we characterize the dust depletion of several metals from the milky way to distant galaxies. we collected measurements of ism metal column densities from absorption-line spectroscopy in the literature, and in addition, we determined ti and ni column densities from a sample of 70 damped lyman-α absorbers (dlas) toward quasars that were observed at high spectral resolution with the very large telescope (vlt) ultraviolet and visual echelle spectrograph (uves). we used relative ism abundances to estimate the dust depletion of 18 metals (c, p, o, cl, kr, s, ge, mg, si, cu, co, mn, cr, ni, al, ti, zn, and fe) for different environments (the milky way, the magellanic clouds, and dlas toward quasars and towards gamma-ray bursts). we observed overall linear relations between the depletion of each metal and the overall strength of the dust depletion, which we traced with the observed [zn/fe]. the slope of these dust depletion sequences correlates with the condensation temperature of the various elements, that is, the more refractory elements show steeper depletion sequences. in the neutral ism of the magellanic clouds, small deviations from linearity are observed as an overabundance of the α-elements ti, mg, s, and an underabundance of mn, including for metal-rich systems. the ti, mg, and mn deviations completely disappear when we assume that all systems in our sample of ob stars observed toward the magellanic clouds have an α-element enhancement and mn underabundance, regardless of their metallicity. this may imply that the magellanic clouds have recently been enriched in α-elements, potentially through recent bursts of star formation. we also observe an s overabundance in all local galaxies, which is an effect of ionization due to the contribution of their h ii regions to the measured s ii column densities. the observed strong correlations of the depletion sequences of the metals all the way from low-metallicity quasi-stellar object dlas to the milky way suggest that cosmic dust has a common origin, regardless of the star formation history, which, in contrast, varies significantly between these different galaxies. this supports the importance of grain growth in the ism as a significant process of dust production. | dust depletion of metals from local to distant galaxies. i. peculiar nucleosynthesis effects and grain growth in the ism |
according to radiative models, radio galaxies and quasars are predicted to produce gamma rays from the earliest stages of their evolution. exploring their high-energy emission is crucial for providing information on the most energetic processes, the origin and the structure of the newly born radio jets. taking advantage of more than 11 yr of fermi-lat data, we investigate the gamma-ray emission of 162 young radio sources (103 galaxies and 59 quasars), the largest sample of young radio sources used so far for such a gamma-ray study. we separately analyse each source and perform the first stacking analysis of this class of sources to investigate the gamma-ray emission of the undetected sources. we detect significant gamma-ray emission from 11 young radio sources, 4 galaxies, and 7 quasars, including the discovery of significant gamma-ray emission from the compact radio galaxy pks 1007+142 (z = 0.213). the cumulative signal of below-threshold young radio sources is not significantly detected. however, it is about one order of magnitude lower than those derived from the individual sources, providing stringent upper limits on the gamma-ray emission from young radio galaxies (fγ < 4.6 × 10-11 ph cm-2 s-1) and quasars (fγ < 10.1 × 10-11 ph cm-2 s-1), and enabling a comparison with the models proposed. with this analysis of more than a decade of fermi-lat observations, we can conclude that while individual young radio sources can be bright gamma-ray emitters, the collective gamma-ray emission of this class of sources is not bright enough to be detected by fermi-lat. | gamma-ray emission from young radio galaxies and quasars |
we present interstellar matter (ism) and circumgalactic medium (cgm) metallicities for 25 absorption systems associated with isolated star-forming galaxies (≤ft< z\right> =0.28) with 9.4 ≤ log(m */m ⊙) ≤ 10.9 and with absorption detected within (200 kpc). galaxy ism metallicities were measured using hα/[n ii] emission lines from keck/esi spectra. cgm single-phase low-ionization metallicities were modeled using markov chain monte carlo and cloudy analysis of absorption from hst/cos and keck/hires or vlt/uves quasar spectra. we find that the star-forming galaxy ism metallicities follow the observed stellar mass-metallicity relation (1σ scatter 0.19 dex). cgm metallicity shows no dependence with stellar mass and exhibits a scatter of ∼2 dex. all cgm metallicities are lower than the galaxy ism metallicities and are offset by log(dz) = -1.17 ± 0.11. there is no obvious metallicity gradient as a function of impact parameter or virial radius (<2.3σ significance). there is no relationship between the relative cgm-galaxy metallicity and azimuthal angle. we find the mean metallicity differences along the major and minor axes are -1.13 ± 0.18 and -1.23 ± 0.11, respectively. regardless of whether we examine our sample by low/high inclination or low/high impact parameter, or low/high n(h i), we do not find any significant relationship with relative cgm-galaxy metallicity and azimuthal angle. we find that 10/15 low column density systems (logn(h i) < 17.2) reside along the galaxy major axis while high column density systems (logn(h i) ≥ 17.2) reside along the minor axis. this suggests n(h i) could be a useful indicator of accretion/outflows. we conclude that cgm is not well mixed, given the range of galaxy-cgm metallicities, and that metallicity at low redshift might not be a good tracer of cgm processes. on the other hand, we should replace integrated line-of-sight, single-phase metallicities with multiphase, cloud-cloud metallicities, which could be more indicative of the physical processes within the cgm. | the relationship between galaxy ism and circumgalactic gas metallicities |
we report strong linear correlation between shifted velocity and line width of the broad blueshifted [o iii] components in sloan digital sky survey (sdss) quasars. broad blueshifted [o iii] components are commonly treated as indicators of outflows related to a central engine; however, it is still an open question whether the outflows are related to central accretion properties or related to local physical properties of narrow emission-line regions (nlrs). here, the reported strong linear correlation with spearman rank correlation coefficient 0.75 can be expected under the assumption of active galactic nuclei (agns) feedback-driven outflows, through a large sample of 535 sdss quasars with reliable blueshifted broad [o iii] components. moreover, there are very different detection rates for broad blueshifted and broad redshifted [o iii] components in quasars, and no positive correlation can be found between shifted velocity and line width of the broad redshifted [o iii] components, which provides further and strong evidence to reject the possibility of local outflows in nlrs leading to the broad blueshifted [o iii] components in quasars. thus, the strong linear correlation can be treated as strong evidence for the broad blueshifted [o iii] components being better indicators of outflows related to central engine in agns. furthermore, rather than central black hole masses, eddington ratios and continuum luminosities have key roles in the properties of the broad blueshifted [o iii] components in quasars. | on strong correlation between shifted velocity and line width of broad blueshifted [o iii] components in quasars |
more than 200 supermassive black holes (smbhs) of masses $\gtrsim 10^9\, \mathrm{m_{\odot }}$ have been discovered at z ≳ 6. one promising pathway for the formation of smbhs is through the collapse of supermassive stars (smss) with masses $\sim 10^{3}{-}10^{5} \, \mathrm{m_{\odot }}$ into seed black holes which could grow upto few times $10^9\, \mathrm{m_{\odot }}$ smbhs observed at z ∼ 7. in this paper, we explore how smss with masses $\sim 10^{3}{-}10^{5} \, \mathrm{m_{\odot }}$ could be formed via gas accretion and runaway stellar collisions in high-redshift, metal-poor nuclear star clusters (nscs) using idealized n-body simulations. we explore physically motivated accretion scenarios, e.g. bondi-hoyle-lyttleton accretion and eddington accretion, as well as simplified scenarios such as constant accretions. while gas is present, the accretion time-scale remains considerably shorter than the time-scale for collisions with the most massive object (mmo). however, overall the time-scale for collisions between any two stars in the cluster can become comparable or shorter than the accretion time-scale, hence collisions still play a crucial role in determining the final mass of the smss. we find that the problem is highly sensitive to the initial conditions and our assumed recipe for the accretion, due to the highly chaotic nature of the problem. the key variables that determine the mass growth mechanism are the mass of the mmo and the gas reservoir that is available for the accretion. depending on different conditions, smss of masses $\sim 10^{3}{-}10^{5} \, \mathrm{m_{\odot }}$ can form for all three accretion scenarios considered in this work. | formation of supermassive black hole seeds in nuclear star clusters via gas accretion and runaway collisions |
the quasar pds 456 (at redshift ∼0.184) has a prototype ultra-fast outflow (ufo) measured in x-rays. this outflow is highly ionized with relativistic speeds, large total column densities log nh(cm-2) > 23, and large kinetic energies that could be important for feedback to the host galaxy. a uv spectrum of pds 456 obtained with the hubble space telescope in 2000 contains one well-measured broad absorption line (bal) at ∼1346 å (observed) that might be ly α at v ≈ 0.06c or n v λ1240 at v ≈ 0.08c. however, we use photoionization models and comparisons to other outflow quasars to show that these bal identifications are problematic because other lines that should accompany them are not detected. we argue that the uv bal is probably c iv at v ≈ 0.30c. this would be the fastest uv outflow ever reported, but its speed is similar to the x-ray outflow and its appearance overall is similar to relativistic uv bals observed in other quasars. the c iv bal identification is also supported indirectly by the tentative detection of another broad c iv line at v ≈ 0.19c. the high speeds suggest that the uv outflow originates with the x-ray ufo crudely 20-30 rg from the central black hole. we speculate that the c iv bal might form in dense clumps embedded in the x-ray ufo, requiring density enhancements of only ≳0.4 dex compared to clumpy structures already inferred for the soft x-ray absorber in pds 456. the c iv bal might therefore be the first detection of low-ionization clumps proposed previously to boost the opacities in ufos for radiative driving. | does the x-ray outflow quasar pds 456 have a uv outflow at 0.3c? |
we report atacama large millimeter/submillimeter array observations of co(8-7), (9-8), ${{\rm{h}}}_{2}{\rm{o}}({2}_{\mathrm{0,2}}\mbox{--}{1}_{\mathrm{1,1}})$ , and ${\mathrm{oh}}^{+}({1}_{1}\mbox{--}{0}_{1})$ and northern extended millimeter array observations of co(5-4), (6-5), (12-11), and (13-12) toward the z = 6.003 quasar sdss j231038.88+185519.7, aiming to probe the physical conditions of the molecular gas content of this source. we present the best sampled co spectral line energy distribution (sled) at z = 6.003, and analyzed it with the radiative transfer code molpop-cep. fitting the co sled to a one-component model indicates a kinetic temperature tkin = 228 k, molecular gas density $\mathrm{log}(n({{\rm{h}}}_{2})/{\mathrm{cm}}^{-3}$ ) = 4.75, and co column density $\mathrm{log}(n(\mathrm{co})/{\mathrm{cm}}^{-2})=17.5$ ; although, a two-component model better fits the data. in either case, the co sled is dominated by a "warm" and "dense" component. compared to samples of local (ultra) luminous infrared galaxies, starburst galaxies, and high-redshift submillimeter galaxies, j2310+1855 exhibits higher co excitation at (j ≥ 8), like other high-redshift quasars. the high co excitation, together with the enhanced ${l}_{{{\rm{h}}}_{2}{\rm{o}}}/{l}_{\mathrm{ir}}$ , ${l}_{{{\rm{h}}}_{2}{\rm{o}}}/{l}_{\mathrm{co}}$ , and ${l}_{{\mathrm{oh}}^{+}}/{l}_{{{\rm{h}}}_{2}{\rm{o}}}$ ratios, suggests that besides the uv radiation from young massive stars, other mechanisms such as shocks, cosmic-rays, and x-rays might also be responsible for the heating and ionization of the molecular gas. in the nuclear region probed by the molecular emissions lines, any of these mechanisms might be present due to the powerful quasar and the starburst activity. | probing the full co spectral line energy distribution (sled) in the nuclear region of a quasar-starburst system at z = 6.003 |
we present statistics from a survey of intervening mg ii absorption toward 100 quasars with emission redshifts between z = 3.55 and z = 7.09. using infrared spectra from magellan/fire, we detect 280 cosmological mg ii absorbers, and confirm that the comoving line density of {w}r> 0.3 \mathringa mg ii absorbers does not evolve measurably between z = 0.25 and z = 7. this is consistent with our detection of seven mg ii systems at z> 6, redshifts not covered in prior searches. restricting to systems with {w}r> 1 å, there is significant evidence for redshift evolution. these systems roughly double in density between z = 0 and z = 2-3, but decline by an order of magnitude from this peak by z∼ 6. this evolution mirrors that of the global star formation rate density, potentially reflecting a connection between star formation feedback and the strong mg ii absorbers. we compared our results to the illustris cosmological simulation at z = 2-4 by assigning absorption to cataloged dark matter halos and by direct extraction of spectra from the simulation volume. reproducing our results using the former requires circumgalactic mg ii envelopes within halos of progressively smaller mass at earlier times. this occurs naturally if we define the lower integration cutoff using sfr rather than mass. spectra calculated directly from illustris yield too few strong mg ii absorbers. this may arise from unresolved phase space structure of circumgalactic gas, particularly from spatially unresolved turbulent or bulk motions. the presence of circumgalactic magnesium at z> 6 suggests that enrichment of intra-halo gas may have begun before the presumed host galaxies’ stellar populations were mature and dynamically relaxed. this paper includes data gathered with the 6.5 m magellan telescopes located at las campanas observatory, chile. | mg ii absorption at 2 < z < 7 with magellan/fire. iii. full statistics of absorption toward 100 high-redshift qsos |
the width of the broad emission lines in quasars is commonly characterized by either the fwhm or the square root of the second moment of the line profile (σ line) and used as an indicator of the virial velocity of the broad-line region (blr) in the estimation of black hole (bh) mass. we measure fwhm and σ line for hα, hβ, and mg ii broad lines in both the mean and rms spectra of a large sample of quasars from the sloan digital sky survey reverberation mapping project. we introduce a new quantitative recipe to measure σ line that is reproducible, is less susceptible to noise and blending in the wings, and scales with the intrinsic width of the line. we compare the four definitions of line width (fwhm and σ line in mean and rms spectra, respectively) for each of the three broad lines and among different lines. there are strong correlations among different width definitions for each line, providing justification for using the line width measured in single-epoch spectroscopy as a virial velocity indicator. there are also strong correlations among different lines, suggesting that alternative lines to hβ can be used to estimate virial bh masses. we further investigate the correlations between virial bh masses using different line width definitions and the stellar velocity dispersion of the host galaxies and the dependence of line shape (characterized by the ratio fwhm/σ line) on physical properties of the quasar. our results provide further evidence that fwhm is more sensitive to the orientation of a flattened blr geometry than σ line, but the overall comparison between the virial bh mass and host stellar velocity dispersion does not provide conclusive evidence that one particular width definition is significantly better than the others. | the sloan digital sky survey reverberation mapping project: low-ionization broad-line widths and implications for virial black hole mass estimation |
we present a sample of 38 intervening damped lyman α (dla) systems identified towards 100 z > 3.5 quasars, observed during the xq-100 survey. the xq-100 dla sample is combined with major dla surveys in the literature. the final combined sample consists of 742 dlas over a redshift range approximately 1.6 < zabs < 5.0. we develop a novel technique for computing ω_{h i}^dla as a continuous function of redshift, and we thoroughly assess and quantify the sources of error therein, including fitting errors and incomplete sampling of the high column density end of the column density distribution function. there is a statistically significant redshift evolution in ω_{h i}^dla (≥3σ) from z ∼ 2 to z ∼ 5. in order to make a complete assessment of the redshift evolution of ω_{h i}, we combine our high-redshift dla sample with absorption surveys at intermediate redshift and 21-cm emission line surveys of the local universe. although ω_{h i}^dla, and hence its redshift evolution, remains uncertain in the intermediate-redshift regime (0.1 < zabs < 1.6), we find that the combination of high-redshift data with 21-cm surveys of the local universe all yield a statistically significant evolution in ω_{h i} from z ∼ 0 to z ∼ 5 (≥3σ). despite its statistical significance, the magnitude of the evolution is small: a linear regression fit between ω_{h i} and z yields a typical slope of ∼0.17 × 10-3, corresponding to a factor of ∼4 decrease in ω_{h i} between z = 5 and z = 0. | the evolution of neutral gas in damped lyman α systems from the xq-100 survey |
we investigate the recent claim of `photon underproduction crisis' by kollmeier et al. which suggests that the known sources of ultraviolet (uv) radiation may not be sufficient to generate the inferred h i photoionization rate (γ _{h i}) in the low-redshift intergalactic medium. using the updated qso emissivities from the recent studies and our cosmological radiative transfer code developed to estimate the uv background, we show that the qso contributions to γ _{h i} is higher by a factor ∼2 as compared to the previous estimates. using self-consistently computed combinations of star formation rate density and dust attenuation, we show that a typical uv escape fraction of 4 per cent from star-forming galaxies should be sufficient to explain the inferred γ _{h i} by kollmeier et al. interestingly, we find that the contribution from qsos alone can explain the recently inferred γ _{h i} by shull et al. which used the same observational data but different simulation. therefore, we conclude that the crisis is not as severe as it was perceived before and there seems no need to look for alternate explanations such as low luminosity hidden qsos or decaying dark matter particles. | photon underproduction crisis: are qsos sufficient to resolve it? |
accretion at sustained or episodic super-eddington (se) rates has been proposed as a pathway to grow efficiently light seeds produced by pop-iii stars. we investigate if se accretion can be sustained onto a black hole (bh) with mbh ~ 103 m⊙ in the centre of a gas-rich proto-galaxy at z = 15. we perform high-resolution smoothed-particle hydrodynamical simulations, including two different sub-grid models for se accretion, one based on the slim disc paradigm, and one inspired by recent radiation-magnetohydrodynamical simulations by jiang and collaborators. radiative feedback has the form of a thermal dump to surrounding gas particles, with the radiative efficiency being set according to the different se accretion models. we find that, in all simulations, star formation, bh feedback, and interactions between clumps and the bh rapidly quench accretion after ~1 myr, irrespective of the sub-grid model used for accretion. quenching is stronger in the model based on the simulations of jiang and collaborators relative to the slim disc model because of its higher radiative efficiency. the se growth phase is always very brief, lasting a few 0.1 myr. in the most optimistic case, the bh reaches a mass of ~104 m⊙. we extrapolate the final bh masses from z = 15 to z ~ 6, assuming subsequent galaxy mergers will replenish the gas reservoir and trigger new cycles of se accretion. we find that at most bh seeds would grow to ~106 m⊙, comparable to the mass of massive bhs in spiral galaxies such as the milky way, but falling short of the mass of the high-redshift quasars. | super-critical accretion of medium-weight seed black holes in gaseous proto-galactic nuclei |
we use both simulated and real quasar light curves to explore modeling photometric reverberation-mapping (rm) data as a stochastic process. we do this using modifications to our previously developed rm method based on modeling quasar variability as a damped random walk. we consider the feasibility of one- and two-band photometric rm and compare the results with those from spectroscopic rm. we find that our method for two-band photometric rm can be competitive with spectroscopic rm only for strong (large equivalent width) lines like hα and hβ, and that the one-band method is also feasible but requires very high precision photometry. we fail to robustly detect hα lags in single-band quasar light curves from ogle-iii and ogle-iv despite the outstanding cadence and time span of the data, on account of photometric uncertainties in the range 0.02-0.04 mag. simulations suggest that success could be achieved if the photometric uncertainties were of order 0.01 mag. single-band rm for all lines and two-band rm for lower equivalent width lines are likely only feasible for statistical estimates of mean lags for large samples of active galactic nuclei of similar properties (e.g., luminosity) rather than for individual quasars. our approach is directly applicable to the time-domain programs within ongoing and future wide-field imaging surveys and could provide robust lag measurements for an unprecedented number of systems. | application of stochastic modeling to analysis of photometric reverberation mapping data |
intervening metal absorption lines in the spectra of z ≳ 6 quasars are fundamental probes of the ionization state and chemical composition of circumgalactic and intergalactic gas near the end of the reionization epoch. large absorber samples are required to robustly measure typical absorber properties and to refine models of the synthesis, transport, and ionization of metals in the early universe. the ultimate xshooter legacy survey of quasars at z ~ 5.8-6.6 (xqr-30) has obtained high signal-to-noise spectra of 30 luminous quasars, nearly quadrupling the existing sample of 12 high quality z ~ 6 quasar spectra. we use this unprecedented sample to construct a catalogue of 778 systems showing absorption in one or more of mg ii (360 systems), fe ii (184), c ii (46), c iv (479), si iv (127), and n v (13) which span 2 ≲ z ≲ 6.5. this catalogue significantly expands on existing samples of z ≳ 5 absorbers, especially for c iv and si iv which are important probes of the ionizing photon background at high redshift. the sample is 50 per cent (90 per cent) complete for rest-frame equivalent widths w ≳ 0.03 å (0.09 å). we publicly release the absorber catalogue along with completeness statistics and a python script to compute the absorption search path for different ions and redshift ranges. this data set is a key legacy resource for studies of enriched gas from the era of galaxy assembly to cosmic noon, and paves the way for even higher redshift studies with jwst and 30 m-class telescopes. | the xqr-30 metal absorber catalogue: 778 absorption systems spanning 2 ≲ z ≲ 6.5 |
we present a weak gravitational lensing measurement of the external convergence along the line of sight to the quadruply lensed quasar he 0435-1223. using deep r-band images from subaru suprime cam, we observe galaxies down to a 3σ limiting magnitude of ∼26 mag resulting in a source galaxy density of 14 galaxies per square arcminute after redshift-based cuts. using an inpainting technique and multiscale entropy filtering algorithm, we find that the region in close proximity to the lens has an estimated external convergence of κ =-0.012^{+0.020}_{-0.013} and is hence marginally underdense. we also rule out the presence of any halo with a mass greater than mvir = 1.6 × 1014h-1m⊙ (68 per cent confidence limit). our results, consistent with previous studies of this lens, confirm that the intervening mass along the line of sight to he 0435-1223 does not affect significantly the cosmological results inferred from the time-delay measurements of that specific object. | h0licow viii. a weak-lensing measurement of the external convergence in the field of the lensed quasar he 0435-1223 |
we extend previous searches for x-ray spectral modulations induced by alp-photon conversion to a variety of new sources, all consisting of quasars or agns located in or behind galaxy clusters. we consider a total of seven new sources, with data drawn from the chandra archive. in all cases the spectrum is well fit by an absorbed power-law with no evidence for spectral modulations, allowing constraints to be placed on the alp-photon coupling parameter gaγγ. two sources are particularly good: the seyfert galaxy 2e3140 in a1795 and the agn ngc3862 within the cluster a1367, leading to 95% bounds for light alps (ma lesssim 10-12 ev) of gaγγ lesssim 1.5 × 10-12 gev-1 and gaγγ lesssim 2.4 × 10-12 gev-1 respectively. | constraints on axion-like particles from non-observation of spectral modulations for x-ray point sources |
measurement of the red damping wing of neutral hydrogen in quasar spectra provides a probe of the epoch of reionization in the early universe. such quantification requires precise and unbiased estimates of the intrinsic continua near lyman-$\alpha$ (ly$\alpha$), a challenging task given the highly variable ly$\alpha$ emission profiles of quasars. here, we introduce a fully probabilistic approach to intrinsic continua prediction. we frame the problem as a conditional density estimation task and explicitly model the distribution over plausible blue-side continua ($1190\ \unicode{xc5} \leq \lambda_{\text{rest}} < 1290\ \unicode{xc5}$) conditional on the red-side spectrum ($1290\ \unicode{xc5} \leq \lambda_{\text{rest}} < 2900\ \unicode{xc5}$) using normalizing flows. our approach achieves state-of-the-art precision and accuracy, allows for sampling one thousand plausible continua in less than a tenth of a second, and can natively provide confidence intervals on the blue-side continua via monte carlo sampling. we measure the damping wing effect in two $z>7$ quasars and estimate the volume-averaged neutral fraction of hydrogen from each, finding $\bar{x}_\text{hi}=0.304 \pm 0.042$ for ulas j1120+0641 ($z=7.09$) and $\bar{x}_\text{hi}=0.384 \pm 0.133$ for ulas j1342+0928 ($z=7.54$). | fully probabilistic quasar continua predictions near lyman-{\\alpha} with conditional neural spline flows |
we present results from a comprehensive study of ultrafast outflows (ufos) detected in a sample of 14 quasars, 12 of which are gravitationally lensed, in a redshift range of 1.41-3.91, near the peak of the active galactic nucleus (agn) and star formation activity. new xmm-newton observations are presented for six of them, which were selected to be lensed and contain a narrow absorption line (nal) in their uv spectra. another lensed quasar was added to the sample, albeit already studied because it was not searched for ufos. the remaining seven quasars of our sample are known to contain ufos. the main goals of our study are to infer the outflow properties of high-z quasars, constrain their outflow induced feedback, study the relationship between the outflow properties and the properties of the ionizing source, and compare these results to those of nearby agn. our study adds six new detections (> 99% confidence) of ufos at z > 1.4, almost doubling the current number of cases. based on our survey of six quasars selected to contain a nal and observed with xmm-newton, the coexistence of intrinsic uv nals and ufos is found to be significant in >83% of these quasars suggesting a link between multiphase agn feedback properties of the meso- and microscale. the kinematic luminosities of the ufos of our high-z sample are large compared to their bolometric luminosities (median of lk/lbol ≳ 50%). this suggests they provide efficient feedback to influence the evolution of their host galaxies and that magnetic driving may be a significant contributor to their acceleration. | multiphase powerful outflows detected in high-z quasars |
while x-ray emission from active galactic nuclei (agn) is common, the detailed physics behind this emission is not well understood. this is in part because high quality broad-band spectra are required to precisely derive fundamental parameters of x-ray emission, such as the photon index, folding energy, and reflection coefficient. here, we present values of such parameters for 33 agn observed as part of the 105-month swift/bat campaign and with coordinated archival xmm-newton and nustar observations. we look for correlations between the various coronal parameters in addition to correlations between coronal parameters and physical properties, such as black hole mass and eddington ratio. using our empirical model, we find good fits to almost all of our objects. the folding energy was constrained for 30 of our 33 objects. when comparing seyfert 1-1.9 to seyfert 2 galaxies, a k-s test indicates that seyfert 2 agn have lower eddington ratios and photon indices than seyfert 1-1.9 objects with p-values of 5.6 × 10-5 and 7.5 × 10-3, respectively. we recover a known correlation between photon index and reflection coefficient as well as the x-ray baldwin effect. finally, we find that the inclusion of the high-energy swift/bat data significantly reduces the uncertainties of spectral parameters as compared to fits without the bat data. | fundamental x-ray corona parameters of swift/bat agn |
magnetic fields have an important role in the evolution of interstellar medium and star formation1,2. as the only direct probe of interstellar field strength, credible zeeman measurements remain sparse owing to the lack of suitable zeeman probes, particularly for cold, molecular gas3. here we report the detection of a magnetic field of +3.8 ± 0.3 microgauss through the h i narrow self-absorption (hinsa)4,5 towards l15446,7—a well-studied prototypical prestellar core in an early transition between starless and protostellar phases8-10 characterized by a high central number density11 and a low central temperature12. a combined analysis of the zeeman measurements of quasar h i absorption, h i emission, oh emission and hinsa reveals a coherent magnetic field from the atomic cold neutral medium (cnm) to the molecular envelope. the molecular envelope traced by the hinsa is found to be magnetically supercritical, with a field strength comparable to that of the surrounding diffuse, magnetically subcritical cnm despite a large increase in density. the reduction of the magnetic flux relative to the mass, which is necessary for star formation, thus seems to have already happened during the transition from the diffuse cnm to the molecular gas traced by the hinsa. this is earlier than envisioned in the classical picture where magnetically supercritical cores capable of collapsing into stars form out of magnetically subcritical envelopes13,14. | an early transition to magnetic supercriticality in star formation |
characterizing the physical conditions (density, temperature, ionization state, metallicity, etc) of the interstellar medium is critical to improving our understanding of the formation and evolution of galaxies. in this work, we present a multi-line study of the interstellar medium in the host galaxy of a quasar at z ≈ 6.4, that is, when the universe was 840 myr old. this galaxy is one of the most active and massive objects emerging from the dark ages and therefore represents a benchmark for models of the early formation of massive galaxies. we used the atacama large millimeter array to target an ensemble of tracers of ionized, neutral, and molecular gas, namely the following fine-structure lines: [o iii] 88 μm, [n ii] 122 μm, [c ii] 158 μm, and [c i] 370 μm - as well as the rotational transitions of co(7-6), co(15-14), co(16-15), and co(19-18); oh 163.1 μm and 163.4 μm; along with h2o 3(0,3)-2(1,2), 3(3,1)-4(0,4), 3(3,1)-3(2,2), 4(0,4)-3(1,3), and 4(3,2)-4(2,3). all the targeted fine-structure lines were detected, along with half of the targeted molecular transitions. by combining the associated line luminosities with the constraints on the dust temperature from the underlying continuum emission and predictions from photoionization models of the interstellar medium, we find that the ionized phase accounts for about one-third of the total gaseous mass budget and is responsible for half of the total [c ii] emission. this phase is characterized by a high density (n ∼ 180 cm−3) that typical of hii regions. the spectral energy distribution of the photoionizing radiation is comparable to that emitted by b-type stars. star formation also appears to be driving the excitation of the molecular medium. we find marginal evidence for outflow-related shocks in the dense molecular phase, but not in other gas phases. this study showcases the power of multi-line investigations in unveiling the properties of the star-forming medium in galaxies at cosmic dawn. | a comprehensive view of the interstellar medium in a quasar host galaxy at z ≈ 6.4 |
we observed 20 palomar-green quasars at low redshift (z < 0.5) with total flux density >1 mjy, including four radio-loud quasars (rlqs) and 16 radio-quiet quasars (rqqs), using the very long baseline array (vlba) at 5 ghz. 10 rqqs are clearly detected in the vlba images, and a compact radio core is identified in eight of them, indicating the prevalence of active galactic nucleus (agn)-related radio emission in this flux-density-limited rqq sample. the rqqs and rlqs in our sample have a division at ~30 mjy. the radio emission from rqqs appears to be the result of a combination of star formation and agn-associated activities. all rqqs in our sample have a 5 ghz flux density ratio of very large array (vla) a-array to d-array $f_{\rm c} = s_{\rm a}^{\rm vla}/s_{\rm d}^{\rm vla}$ above 0.2. the rqqs with fa (vlba and vla flux density ratio $s^{\rm vlba}/s_{\rm a}^{\rm vla}) \gt 0.2$ versus fa < 0.2 show significant differences in morphology, compactness, and total flux density. fa of rqqs is systematically lower than that of rlqs, probably due to the extended jets or relic jets of rqqs on tens to hundreds parsecs that are resolved out in vlba images. future larger samples, especially with the addition of milliarcsec resolution radio images of rqqs with total flux densities below 1 mjy, can test the conclusions of this paper and contribute to the understanding of the radio emission mechanism of rqqs, and the dichotomy and physical connection between rqqs and rlqs. | vlbi observations of a sample of palomar-green quasars - i. parsec-scale morphology |
we introduce a new model for the accretion and feedback of supermassive black hole (smbh) binaries to the ketju code, which enables us to resolve the evolution of smbh binaries down to separations of tens of schwarzschild radii in gas-rich galaxy mergers. our subgrid binary accretion model extends the widely used bondi-hoyle-lyttleton accretion into the binary phase and incorporates preferential mass accretion on to the secondary smbh, which is motivated by results from small-scale hydrodynamical circumbinary disc simulations. we perform idealized gas-rich disc galaxy merger simulations using pure thermal or pure kinetic active galactic nuclei (agns) feedback. our binary accretion model provides more physically motivated smbh mass ratios, which are one of the key parameters for computing gravitational wave (gw) induced recoil velocities. the merger time-scales of our simulated smbh binaries are in the range tmerge ~ 10-400 myr. prograde in-plane equal-mass galaxy mergers lead to the shortest merger time-scales, as they experience the strongest starbursts, with the ensuing high stellar density resulting in a rapid smbh coalescence. compared to the thermal agn feedback, the kinetic agn feedback predicts longer merger time-scales and results in more core-like stellar profiles, as it is more effective in removing gas from the galaxy centre and quenching star formation. this suggests that the agn feedback implementation plays a critical role in modelling smbh coalescences. our model will be useful for improving the modelling of smbh mergers in gas-rich galaxies, the prime targets for the upcoming lisa gw observatory. | modelling the accretion and feedback of supermassive black hole binaries in gas-rich galaxy mergers |
we report on the first results of the polami (polarimetric monitoring of agns with millimetre wavelengths) programme, a simultaneous 3.5 and 1.3 mm full-stokes-polarization monitoring of a sample of 36 of the brightest active galactic nuclei in the northern sky with the iram 30 m telescope. through a systematic statistical study of data taken from 2006 october (from 2009 december for the case of the 1.3 mm observations) to 2014 august, we characterize the variability of the total flux density and linear polarization. we find that all sources in the sample are highly variable in total flux density at both 3.5 and 1.3 mm, as well as in spectral index, which (except in particularly prominent flares) is found to be optically thin between these two wavelengths. the total flux-density variability at 1.3 mm is found, in general, to be faster, and to have larger fractional amplitude and flatter power-spectral-density slopes than at 3.5 mm. the polarization degree is on average larger at 1.3 mm than at 3.5 mm, by a factor of 2.6. the variability of linear polarization degree is faster and has higher fractional amplitude than for total flux density, with the typical time-scales during prominent polarization peaks being significantly faster at 1.3 mm than at 3.5 mm. the polarization angle at both 3.5 and 1.3 mm is highly variable. most of the sources show one or two excursions of >180° on time-scales from a few weeks to about a year during the course of our observations. the 3.5 and 1.3 mm polarization angle evolution follows each other rather well, although the 1.3 mm data show a clear preference to more prominent variability on the short time-scales, i.e. weeks. the data are compatible with multizone models of conical jets involving smaller emission regions for the shortest-wavelength emitting sites. such smaller emitting regions should also be more efficient in energising particle populations, as implied by the coherent evolution of the spectral index and the total flux density during flaring activity of strong enough sources. the data also favour the integrated emission at 1.3 mm to have better ordered magnetic fields than the one at 3.5 mm. | polami: polarimetric monitoring of active galactic nuclei at millimetre wavelengths - iii. characterization of total flux density and polarization variability of relativistic jets |
the flux ratios in the multiple images of gravitationally lensed quasars can provide evidence for dark matter substructure in the halo of the lensing galaxy if the flux ratios differ from those predicted by a smooth model of the lensing galaxy mass distribution. however, it is also possible that baryonic structures in the lensing galaxy, such as edge-on discs, can produce flux-ratio anomalies. in this work, we present the first statistical analysis of flux-ratio anomalies due to baryons from a numerical simulation perspective. we select galaxies with various morphological types in the illustris simulation and ray trace through the simulated haloes, which include baryons in the main lensing galaxies but exclude any substructures, in order to explore the pure baryonic effects. our ray-tracing results show that the baryonic components can be a major contribution to the flux-ratio anomalies in lensed quasars and that edge-on disc lenses induce the strongest anomalies. we find that the baryonic components increase the probability of finding high flux-ratio anomalies in the early-type lenses by about 8 per cent and by about 10-20 per cent in the disc lenses. the baryonic effects also induce astrometric anomalies in 13 per cent of the mock lenses. our results indicate that the morphology of the lens galaxy becomes important in the analysis of flux-ratio anomalies when considering the effect of baryons, and that the presence of baryons may also partially explain the discrepancy between the observed (high) anomaly frequency and what is expected due to the presence of subhaloes as predicted by the cold dark matter simulations. | flux-ratio anomalies from discs and other baryonic structures in the illustris simulation |
supermassive black holes at the centre of galactic nuclei mostly grow in mass through gas accretion over cosmic time. this process also modifies the angular momentum (or spin) of black holes, both in magnitude and in orientation. despite being often neglected in galaxy formation simulations, spin plays a crucial role in modulating accretion power, driving jet feedback, and determining recoil velocity of coalescing black hole binaries. we present a new accretion model for the moving-mesh code arepo that incorporates (i) mass accretion through a thin α-disc and (ii) spin evolution through the bardeen-petterson effect. we use a diverse suite of idealized simulations to explore the physical connection between spin evolution and larger scale environment. we find that black holes with mass ≲107 m⊙ experience quick alignment with the accretion disc. this favours prolonged phases of spin-up, and the spin direction evolves according to the gas inflow on time-scales as short as ≲100 myr, which might explain the observed jet direction distribution in seyfert galaxies. heavier black holes (≳108 m⊙) are instead more sensitive to the local gas kinematic. here, we find a wider distribution in spin magnitudes: spin-ups are favoured if gas inflow maintains a preferential direction, and spin-downs occur for nearly isotropic infall, while the spin direction does not change much over short time-scales ∼100 myr. we therefore conclude that supermassive black holes with masses ≳5 × 108 m⊙ may be the ideal testbed to determine the main mode of black hole fuelling over cosmic time. | galactic nuclei evolution with spinning black holes: method and implementation |
the gigahertz peaked spectrum (gps) sources, compact steep spectrum (css) radio sources, and high-frequency peaker (hfp) radio sources are thought to be young radio active galactic nuclei (agns) at the early stage of agn evolution. we investigated the optical properties of the largest sample of 126 young radio agns based on the spectra in sdss dr12. we find that the black hole masses mbh range from 107.32 to 109.84 m_{⊙} and the eddington ratios redd vary from 10-4.93 to 100.37, suggesting that young radio agns have various accretion activities and not all are accreting at high accretion rate. our young radio sources generally follow the evolutionary trend towards large-scale radio galaxies with increasing linear size and decreasing accretion rate in the radio power-linear size diagram. the radio properties of low-luminosity young radio agns with low redd are discussed. the line width of [o iii] λ5007 core (σ[o iii]) is found to be a good surrogate of stellar velocity dispersion σ*. the radio luminosity l_{5 ghz} correlates strongly with [o iii] core luminosity l[o iii], suggesting that radio activity and accretion are closely related in young radio sources. we find one object that can be defined as a narrow-line seyfert 1 galaxy, representing a population of young agns with both young jet and early accretion activity. the optical variabilities of 15 quasars with multi-epoch spectroscopy were investigated. our results show that the optical variability in young agn quasars presents low variations (≤ 60 per cent) similar to the normal radio-quiet quasars. | investigation on young radio agns based on sdss spectroscopy |
context. the primary x-ray emission in active galactic nuclei (agns) is widely believed to be due to comptonisation of the thermal radiation from the accretion disc in a corona of hot electrons. the resulting spectra can, in first approximation, be modelled with a cut-off power law, the photon index and the high-energy roll-over encoding information on the physical properties of the x ray emitting region. the photon index and the high-energy curvature of agns (γ, ec) have been largely studied since the launch of x-ray satellites operating above 10 kev. however, high-precision measurements of these two observables have only been obtained in recent years thanks to the unprecedented sensitivity of nustar up to 79 kev.aims: we aim at deriving relations between γ, ec phenomenological parameters and the intrinsic properties of the x-ray-emitting region (the hot corona), namely the optical depth and temperature.methods: we use moca (monte carlo code for comptonisation in astrophysics) to produce synthetic spectra for the case of an agn with mbh = 1.5 × 108 m⊙ and ṁ = 0.1 and then compared them with the widely used power-law model with an exponential high-energy cutoff.results: we provide phenomenological relations relating γ and ec with the opacity and temperature of the coronal electrons for the case of spherical and slab-like coronae. these relations give origin to a well defined parameter space which fully contains the observed values. exploiting the increasing number of high-energy cut-offs quoted in the literature, we report on the comparison of physical quantities obtained using moca with those estimated using commonly adopted spectral comptonisation models. finally, we discuss the negligible impact of different black hole masses and accretion rates on the inferred relations. | relations between phenomenological and physical parameters in the hot coronae of agns computed with the moca code |
black hole mass measurements outside the local universe are critically important to derive the growth of supermassive black holes over cosmic time, and to study the interplay between black hole growth and galaxy evolution. in this paper, we present two measurements of supermassive black hole masses from reverberation mapping (rm) of the broad c iv emission line. these measurements are based on multiyear photometry and spectroscopy from the dark energy survey supernova program (des-sn) and the australian dark energy survey (ozdes), which together constitute the ozdes rm program. the observed reverberation lag between the des continuum photometry and the ozdes emission line fluxes is measured to be 358^{+126}_{-123} and 343^{+58}_{-84} d for two quasars at redshifts of 1.905 and 2.593, respectively. the corresponding masses of the two supermassive black holes are 4.4 × 109 and 3.3 × 109 m⊙, which are among the highest redshift and highest mass black holes measured to date with rm studies. we use these new measurements to better determine the c iv radius-luminosity relationship for high-luminosity quasars, which is fundamental to many quasar black hole mass estimates and demographic studies. | c iv black hole mass measurements with the australian dark energy survey (ozdes) |
context. active galactic nucleus (agn) driven outflows are invoked in numerical simulations to reproduce several observed properties of local galaxies. the z > 1 epoch is of particular interest as it was during this time that the volume averaged star formation and the accretion rate of black holes were at their maximum. radiatively driven outflows are therefore believed to be common during this epoch.aims: we aim to trace and characterize outflows in agn hosts with high mass accretion rates at z > 1 using integral field spectroscopy. we obtain spatially resolved kinematics of the [o iii] λ5007 line in two targets which reveal the morphology and spatial extension of the outflows.methods: we present sinfoni observations in the j band and the h + k band of five agns at 1.2 < z < 2.2. to maximize the chance of observing radiatively driven outflows, our sample was pre-selected based on peculiar values of the eddington ratio and the hydrogen column density of the surrounding interstellar medium. we observe high velocity (~600-1900 km s-1) and kiloparsec scale extended ionized outflows in at least three of our targets, using [o iii] λ5007 line kinematics tracing the agn narrow line region. we estimate the total mass of the outflow, the mass outflow rate, and the kinetic power of the outflows based on theoretical models and report on the uncertainties associated with them.results: we find mass outflow rates of ~1-10 m⊙/yr for the sample presented in this paper. based on the high star formation rates of the host galaxies, the observed outflow kinetic power, and the expected power due to the agn, we infer that both star formation and agn radiation could be the dominant source for the outflows. the outflow models suffer from large uncertainties, hence we call for further detailed observations for an accurate determination of the outflow properties to confirm the exact source of these outflows. | tracing outflows in the agn forbidden region with sinfoni |
we report on detections with the atacama large millimeter/sub-millimeter array of the far-infrared [o iii] 88 μm line and the underlying dust continuum in two quasars in the reionization epoch, j205406.48-000514.8 (hereafter j2054-0005) at z = 6.0391 ± 0.0002 and j231038.88+185519.7 (hereafter j2310+1855) at z = 6.0035 ± 0.0007. the [o iii] luminosities of j2054-0005 and j2310+1855 are l[o iii] = (6.8 ± 0.6) × 109 and (2.4 ± 0.6) × 109 l⊙, corresponding to ∼0.05% and 0.01% of the total infrared luminosity, ltir, respectively. combining these [o iii] luminosities with [c ii] 158 μm luminosities in the literature, we find that j2054-0005 and j2310+1855 have [o iii]-to-[c ii] luminosity ratios of 2.1 ± 0.4 and 0.3 ± 0.1, respectively, the latter of which is the lowest among objects so far reported at z > 6. combining [o iii] observations at z ≈ 6-9 from our study and the literature, we identify the [o iii] line deficit: objects with a larger ltir (total infrared luminosity) have lower l[o iii]-to-ltir ratios. furthermore, we also find that the anti-correlation is shifted toward a higher ltir value when compared with the local [o iii] line deficit. | detections of [o iii] 88 μm in two quasars in the reionization epoch |
we present a new population of z > 2 dust-reddened, type 1 quasars with 0.5 ≲ e(b - v) ≲ 1.5, selected using near-infrared (nir) imaging data from the ukidss-las (large area survey), eso-vhs (european southern obseratory-vista hemisphere survey) and wise surveys. nir spectra obtained using the very large telescope for 24 new objects bring our total sample of spectroscopically confirmed hyperluminous (>1013 l⊙), high-redshift dusty quasars to 38. there is no evidence for reddened quasars having significantly different hα equivalent widths relative to unobscured quasars. the average black hole masses (∼109-1010 m⊙) and bolometric luminosities (∼1047 erg s-1) are comparable to the most luminous unobscured quasars at the same redshift, but with a tail extending to very high luminosities of ∼1048 erg s-1. 66 per cent of the reddened quasars are detected at >3σ at 22 μm by wise. the average 6-μm rest-frame luminosity is log10(l6 μm/ erg s-1) = 47.1 ± 0.4, making the objects among the mid-infrared brightest active galactic nuclei (agn) currently known. the extinction-corrected space density estimate now extends over three magnitudes (-30 < mi < -27) and demonstrates that the reddened quasar luminosity function is significantly flatter than that of the unobscured quasar population at z = 2-3. at the brightest magnitudes, mi ≲ -29, the space density of our dust-reddened population exceeds that of unobscured quasars. a model where the probability that a quasar becomes dust reddened increases at high luminosity is consistent with the observations and such a dependence could be explained by an increase in luminosity and extinction during agn-fuelling phases. the properties of our obscured type 1 quasars are distinct from the heavily obscured, compton-thick agn that have been identified at much fainter luminosities and we conclude that they likely correspond to a brief evolutionary phase in massive galaxy formation. | heavily reddened type 1 quasars at z > 2 - i. evidence for significant obscured black hole growth at the highest quasar luminosities |
we present the rest-frame optical spectral properties of 155 luminous quasars at 3.3 < z < 6.4 taken with the akari space telescope, including the first detection of the hα emission line as far out as z ∼ 6. we extend the scaling relation between the rest-frame optical continuum and the line luminosity of active galactic nuclei (agns) to the high-luminosity, high-redshift regime that has rarely been probed before. remarkably, we find that a single log-linear relation can be applied to the 5100 å and hα agn luminosities over a wide range of luminosity (1042 < l5100 < 1047 ergs s-1) or redshift (0 < z < 6), suggesting that the physical mechanism governing this relation is unchanged from z = 0 to 6, over five decades in luminosity. similar scaling relations are found between the optical and the uv continuum luminosities or line widths. applying the scaling relations to the hβ black hole (bh) mass (mbh) estimator of local agns, we derive the mbh estimators based on the hα, mg ii, and c iv lines, finding that the uv-line-based masses are overall consistent with the balmer-line-based, but with a large intrinsic scatter of 0.40 dex for the c iv estimates. our 43 mbh estimates from hα confirm the existence of bhs as massive as ∼ 1010 m⊙ out to z ∼ 5 and provide a secure footing for previous results from mg ii-line-based studies that a rapid mbh growth has occurred in the early universe. | rest-frame optical spectra and black hole masses of 3 < z < 6 quasars |
the direct collapse model for the formation of massive seed black holes in the early universe attempts to explain the observed number density of supermassive black holes (smbhs) at z ∼ 6 by assuming that they grow from seeds with masses m > 104 m⊙ that form by the direct collapse of metal-free gas in atomic cooling haloes in which h2 cooling is suppressed by a strong extragalactic radiation field. the viability of this model depends on the strength of the radiation field required to suppress h2 cooling, jcrit: if this is too large, then too few seeds will form to explain the observed number density of smbhs. in order to determine jcrit reliably, we need to be able to accurately model the formation and destruction of h2 in gas illuminated by an extremely strong radiation field. in this paper, we use a reaction-based reduction technique to analyse the chemistry of h2 in these conditions, allowing us to identify the key chemical reactions that are responsible for determining the value of jcrit. we construct a reduced network of 26 reactions that allows us to determine jcrit accurately, and compare it with previous treatments in the literature. we show that previous studies have often omitted one or more important chemical reactions, and that these omissions introduce an uncertainty of up to a factor of 3 into previous determinations of jcrit. | simulating the formation of massive seed black holes in the early universe - i. an improved chemical model |
we present new atacama large millimeter/submillimeter array (alma) observations of the dust continuum and [c ii] 158 μm fine structure line emission toward a far-infrared-luminous quasar, ulas j131911.29+095051.4 at z = 6.13, and combine the new cycle 1 data with alma cycle 0 data. the combined data have an angular resolution of ∼0.″3, and resolve both the dust continuum and the [c ii] line emission on a few kiloparsec scales. the [c ii] line emission is more irregular than that of the dust continuum emission, which suggests different distributions between the dust and the [c ii]-emitting gas. the combined data confirm the [c ii] velocity gradient that we had previously detected in a lower-resolution alma image from the cycle 0 data alone. we apply a tilted ring model to the [c ii] velocity map to obtain a rotation curve, and constrain the circular velocity to be 427 ± 55 km s-1 at a radius of 3.2 kpc with an inclination angle of 34°. we measure the dynamical mass within the 3.2 kpc region to be {13.4}-5.3+7.8 × {10}10 {m}⊙ . this yields a black-hole and host galaxy mass ratio of {0.020}-0.007+0.013, which is about {4}-2+3 times higher than that of the present-day {m}bh}/{m}bulge} ratio. this suggests that the supermassive black hole grows the bulk of its mass before the formation of most of the stellar mass in this quasar host galaxy in the early universe. | gas dynamics of a luminous z = 6.13 quasar ulas j1319+0950 revealed by alma high-resolution observations |
we present high angular resolution multiwavelength data of the 3c 298 radio-loud quasar host galaxy (z = 1.439) taken using the w.m. keck observatory osiris integral field spectrograph (ifs) with adaptive optics, the atacama large millimeter/submillimeter array (alma), the hubble space telescope (hst) wfc3, and the very large array (vla). extended emission is detected in the rest-frame optical nebular emission lines hβ, [o iii], hα, [n ii], and [s ii], as well as in the molecular lines co (j = 3-2) and (j = 5-4). along the path of the relativistic jets of 3c 298, we detect conical outflows in ionized gas emission with velocities of up to 1700 {km} {{{s}}}-1 and an outflow rate of 450-1500 {m}⊙{{yr}}-1 extended over 12 kpc. near the spatial center of the conical outflow, co (j = 3-2) emission shows a molecular gas disk with a rotational velocity of ±150 {km} {{{s}}}-1 and total molecular mass ({m}{{{h}}2}) of 6.6+/- 0.36× {10}9 {m}⊙ . on the blueshifted side of the molecular disk, we observe broad extended emission that is due to a molecular outflow with a rate of 2300 {m}⊙{{yr}}-1 and depletion timescale of 3 myr. we detect no narrow hα emission in the outflow regions, suggesting a limit on star formation of 0.3 {m}⊙{{yr}}-1 {{kpc}}-2. quasar-driven winds are evacuating the molecular gas reservoir, thereby directly impacting star formation in the host galaxy. the observed mass of the supermassive black hole is {10}9.37{--9.56} {m}⊙ , and we determine a dynamical bulge mass of {m}{bulge}=1{--}1.7× {10}10\tfrac{r}{1.6 {kpc}} {m}⊙ . the bulge mass of 3c 298 lies 2-2.5 orders of magnitude below the expected value from the local galactic bulge—supermassive black hole mass ({m}{bulge}{--}{m}{bh}) relationship. a second galactic disk observed in nebular emission is offset from the quasar by 9 kpc, suggesting that the system is an intermediate-stage merger. these results show that galactic-scale negative feedback is occurring early in the merger phase of 3c 298, well before the coalescence of the galactic nuclei and assembly on the local {m}{bulge}{--}{m}{bh} relationship. | galactic-scale feedback observed in the 3c 298 quasar host galaxy |
we report the detection of a probable γ-ray quasi-periodic oscillation (qpo) of around 314 d in the monthly binned 0.1-300 gev γ-ray fermi-large area telescope light curve of the well-known bl lacertae blazar oj 287. to identify and quantify the qpo nature of the γ-ray light curve of oj 287, we used the lomb-scargle periodogram (lsp), redfit, and weighted wavelet z-transform (wwz) analyses. we briefly discuss possible emission models for radio-loud active galactic nuclei that can explain a γ-ray qpo of such a period in a blazar. | a possible γ-ray quasi-periodic oscillation of ∼314 days in the blazar oj 287 |
a significant tension has become manifest between the current expansion rate of our universe measured from the cosmic microwave background by the planck satellite and from local distance probes, which has prompted for interpretations of that as evidence of new physics. within conventional cosmology a likely source of this discrepancy is identified here as a matter density fluctuation around the cosmic average of the 40 mpc environment in which the calibration of supernovae type ia separations with cepheids and nearby absolute distance anchors is performed. inhomogeneities on this scale easily reach 40% and more. in that context, the discrepant expansion rates serve as evidence of residing in an underdense region of δenv ≈ - 0.5 ± 0.1. the probability for finding this local expansion rate given the planck data lies at the 95% confidence level. likewise, a hypothetical equivalent local data set with mean expansion rate equal to that of planck, while statistically favoured, would not gain strong preference over the actual data in the respective bayes factor. these results therefore suggest borderline consistency between the local and planck measurements of the hubble constant. generally accounting for the environmental uncertainty, the local measurement may be reinterpreted as a constraint on the cosmological hubble constant of h0 = 74.7-4.2+5.8 km/s/mpc. the current simplified analysis may be augmented with the employment of the full available data sets, an impact study for the immediate ≲10 mpc environment of the distance anchors, more prone to inhomogeneities, as well as expansion rates measured by quasar lensing, gravitational waves, currently limited to the same 40 mpc region, and local galaxy distributions. | consistency of the local hubble constant with the cosmic microwave background |
we present new measurements of the time delays of wfi2033-4723. the data sets used in this work include 14 years of data taken at the 1.2 m leonhard euler swiss telescope, 13 years of data from the smarts 1.3 m telescope at las campanas observatory and a single year of high-cadence and high-precision monitoring at the mpia 2.2 m telescope. the time delays measured from these different data sets, all taken in the r-band, are in good agreement with each other and with previous measurements from the literature. combining all the time-delay estimates from our data sets results in δtab = 36.2+0.7-0.8 days (2.1% precision), δtac = -23.3+1.2-1.4 days (5.6%) and δtbc = -59.4+1.3-1.3 days (2.2%). in addition, the close image pair a1-a2 of the lensed quasars can be resolved in the mpia 2.2 m data. we measure a time delay consistent with zero in this pair of images. we also explore the prior distributions of microlensing time-delay potentially affecting the cosmological time-delay measurements of wfi2033-4723. our time-delay measurements are not precise enough to conclude that microlensing time delay is present or absent from the data. this work is part of a h0licow series focusing on measuring the hubble constant from wfi2033-4723. full light curves of the four data sets 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/629/a97 | cosmograil. xviii. time delays of the quadruply lensed quasar wfi2033-4723 |
in the upcoming decade, large astronomical surveys will discover millions of transients raising unprecedented data challenges in the process. only the use of the machine learning algorithms can process such large data volumes. most of the discovered transients will belong to the known classes of astronomical objects. however, it is expected that some transients will be rare or completely new events of unknown physical nature. the task of finding them can be framed as an anomaly detection problem. in this work, we perform for the first time an automated anomaly detection analysis in the photometric data of the open supernova catalog (osc), which serves as a proof of concept for the applicability of these methods to future large-scale surveys. the analysis consists of the following steps: (1) data selection from the osc and approximation of the pre-processed data with gaussian processes, (2) dimensionality reduction, (3) searching for outliers with the use of the isolation forest algorithm, and (4) expert analysis of the identified outliers. the pipeline returned 81 candidate anomalies, 27 (33 per cent) of which were confirmed to be from astrophysically peculiar objects. found anomalies correspond to a selected sample of 1.4 per cent of the initial automatically identified data sample of approximately 2000 objects. among the identified outliers we recognized superluminous supernovae, non-classical type ia supernovae, unusual type ii supernovae, one active galactic nucleus and one binary microlensing event. we also found that 16 anomalies classified as supernovae in the literature are likely to be quasars or stars. our proposed pipeline represents an effective strategy to guarantee we shall not overlook exciting new science hidden in the data we fought so hard to acquire. all code and products of this investigation are made publicly available.1 | anomaly detection in the open supernova catalog |
we present hubble space telescope 1.4-1.6 μm images of the hosts of 10 extremely red quasars (erqs) and six type 2 quasar candidates at z = 2-3. erqs, whose bolometric luminosities range between 1047 and 1048 erg s-1, show spectroscopic signs of powerful ionized winds, whereas type 2 quasar candidates are less luminous and show only mild outflows. after performing careful subtraction of the quasar light, we clearly detect almost all host galaxies. the median rest-frame b-band luminosity of the erq hosts in our sample is 10^{11.2} l_{\odot }, or ∼4l* at this redshift. two of the 10 hosts of erqs are in ongoing mergers. the hosts of the type 2 quasar candidates are 0.6 dex less luminous, with 2/6 in likely ongoing mergers. intriguingly, despite some signs of interaction and presence of low-mass companions, our objects do not show nearly as much major merger activity as do high-redshift radio-loud galaxies and quasars. in the absence of an overt connection to major ongoing gas-rich merger activity, our observations are consistent with a model in which the near-eddington accretion and strong feedback of erqs are associated with relatively late stages of mergers resulting in early-type remnants. these results are in some tension with theoretical expectations of galaxy formation models, in which rapid black hole growth occurs within a short time of a major merger. type 2 quasar candidates are less luminous, so they may instead be powered by internal galactic processes. | host galaxies of high-redshift extremely red and obscured quasars |
we present details of the automated radio telescope imaging pipeline (artip) and the results of a sensitive blind search for h i and oh absorbers at z < 0.4 and z < 0.7, respectively. artip is written in python 3.6, extensively uses the common astronomy software application tools and tasks, and is designed to enable the geographically distributed meerkat absorption line survey (mals) team to collaboratively process large volumes of radio interferometric data. we apply it to the first mals data set obtained using the 64-dish meerkat radio telescope and 32 k channel mode of the correlator. with merely 40 minutes on target, we present the most sensitive spectrum of pks 1830-211 ever obtained and characterize the known h i (z = 0.19) and oh (z = 0.89) absorbers. we further demonstrate artip's capabilities to handle realistic observing scenarios by applying it to a sample of 72 bright radio sources observed with the upgraded giant metrewave radio telescope (ugmrt) to blindly search for h i and oh absorbers. we estimate the numbers of h i and oh absorbers per unit redshift to be n21(z ∼ 0.18) < 0.14 and noh(z ∼ 0.40) < 0.12, respectively, and constrain the cold gas covering factor of galaxies at large impact parameters (50 kpc < ρ < 150 kpc) to be less than 0.022. due to the small redshift path, δz ∼ 13 for h i with column density >5.4 × 1019 cm-2, the survey has probed only the outskirts of star-forming galaxies at ρ > 30 kpc. mals with the expected δz ∼ 103-4 will overcome this limitation and provide stringent constraints on the cold gas fraction of galaxies in diverse environments over 0 < z < 1.5. | blind h i and oh absorption line search: first results with mals and ugmrt processed using artip |
we present rest-frame b and i imaging of 35 low-redshift ( $z\lt 0.5$ ) palomar-green quasars using the hubble space telescope wide field camera 3. we perform multicomponent two-dimensional image decomposition to separate the host galaxy from its bright active nucleus, characterize its morphology, and measure its photometric properties. special care is devoted to quantifying the structural parameters of the galaxy bulge, determining its b - i color, and estimating its stellar mass. roughly half of the sample, comprising the less luminous ( ${l}_{5100}\lesssim {10}^{45}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ ) but most high eddington ratio quasars, reside in disk galaxies that are often barred and possess pseudo bulges. the large stellar masses, large effective radii, and faint surface brightnesses suggest that the host galaxies of the most luminous quasars are mostly ellipticals. major mergers constitute only a small percentage (≲20%) of our sample. our quasar sample roughly obeys the scaling relations between black hole mass and host galaxy (bulge, core, total) stellar mass. hosts with black holes more massive than $\sim {10}^{8}\,{m}_{\odot }$ behave similarly to classical bulges and early-type galaxies, while those with less massive black holes, particularly the narrow-line seyfert 1s, are consistent with pseudo bulges in late-type galaxies. the host galaxy bulges, irrespective of whether they are classical or pseudo, follow a relatively tight inverse relation between the effective radius and the mean effective surface brightness of inactive classical bulges and ellipticals. we argue that pseudo bulges experience recent or ongoing nuclear star formation. | the diverse morphology, stellar population, and black hole scaling relations of the host galaxies of nearby quasars |
we study stellar and black hole mass assembly in a sample of 42 infrared-luminous galaxy mergers at z < 0.3 by combining results from radiative transfer modelling with archival measures of molecular gas and black hole mass. the ratios of stellar mass, molecular gas mass, and black hole mass to each other are consistent with those of massive gas-rich galaxies at z < 0.3. the advanced mergers may show increased black hole mass to stellar mass ratios, consistent with the transition from active galactic nucleus (agn) to ellipticals and implying substantial black hole mass growth over the course of the merger. star formation rates are enhanced relative to the local main sequence, by factors of ~100 in the starburst and ~1.8 in the host, respectively. the starburst star formation rates appear distinct to star formation in the main sequence at all redshifts up to at least z ~ 5. starbursts may prefer late-stage mergers, but are observed at any merger stage. we do not find evidence that the starbursts in these low-redshift systems substantially increase the total stellar mass, with a soft upper limit on the stellar mass increase from starburst activity of about a factor of two. in contrast, 12 objects show evidence for super-eddington accretion, associated with late-stage mergers, suggesting that many agn in infrared-luminous mergers go through a super-eddington phase. the super-eddington phase may increase black hole mass by up to an order of magnitude at an accretion efficiency of $42\pm 33{{\ \rm per\ cent}}$ over a period of 44 ± 22 myr. our results imply that super-eddington accretion is an important black hole growth channel in infrared-luminous galaxies at all redshifts. | stellar and black hole assembly in z < 0.3 infrared-luminous mergers: intermittent starbursts versus super-eddington accretion |
we quantify galaxy overdensities around three high-redshift quasars with known [c ii]158 μm companions: pj231-20 (z = 6.59), pj308-21 (z = 6.24), and j0305-3150 (z = 6.61). recent scuba2 imaging revealed the presence of 17 submillimeter galaxies (smgs) with sky separations 0.'7 < θ < 2.'4 from these three quasars. we present alma band 6 follow-up observations of these scuba2-selected smgs to confirm their nature and redshift. we also search for continuum-undetected [c ii]158 μm emitters in the alma pointings and make use of archival muse observations to search for lyα emitters (laes) associated with the quasars. while most of the scuba2-selected sources are detected with alma in the continuum, no [c ii]158 μm line emission could be detected, indicating that they are not at the quasar redshifts. based on the serendipitous detection of co 7-6 and [c i]809 μm emission lines, we find that four smgs in the field of pj231-20 are at z ~ 2.4, which is coincident with the redshift of an mg ii absorber in the quasar rest-frame uv spectrum. we report the discovery of two laes within <0.6 cmpc of pj231-20 at the same redshift, indicating an lae overdensity around this quasar. taken together, these observations provide new constraints on the large-scale excess of lyα- and [c ii]158 μm-emitting galaxies around z > 6 quasars and suggest that only wide-field observations, such as muse, alma, or jwst mosaics, can reveal a comprehensive picture of large-scale structure around quasars in the first billion years of the universe. | constraining galaxy overdensities around three z 6.5 quasars with alma and muse |
we examine the dual [both black hole (bh) active] and offset (one bh active and in distinct galaxies) active galactic nucleus (agn) population (comprising ~ 2000 pairs at $0.5\, \text{kpc}\lesssim \delta r\lt 30\, \text{kpc}$) at z = 2 ~ 3 in the astrid simulation covering (360 cmpc)3. the dual (offset) agn make up 3.0(0.5) per cent of all agn at z = 2. the dual fraction is roughly constant while the offset fraction increases by a factor of 10 from z = 4 ~ 2. compared with the full agn population, duals are characterized by low mbh/m* ratios, high specific star formation rates (ssfr) of $\sim 1\, \text{gyr}^{-1}$, and high eddington ratios (~0.05, double that of single agn). dual agns are formed in major galaxy mergers (typically involving $m_\text{halo}\lt 10^{13}\, m_\odot$), with simular-mass bhs. at small separations (when host galaxies are in the late phase of the merger), duals become 2 ~ 8 times brighter (albeit more obscured) than at larger separations. 80 per cent of the bright, close duals would merge within $\sim 500\, \text{myr}$. notably, the initially less-massive bhs in duals frequently become the brighter agn during galaxy mergers. in offset agn, the active bh is typically ≳ 10 times more massive than its non-active counterpart and than most bhs in duals. offsets are predominantly formed in minor galaxy mergers with the active bh residing in the centre of massive haloes ($m_\text{ halo}\sim 10^{13-14}\, \mathrm{m}_\odot$). in these deep potentials, gas stripping is common and the secondary quickly deactivates. the stripping also leads to inefficient orbital decay amongst offsets, which stall at $\delta r\sim 5\, \text{kpc}$ for a few hundred myrs. | properties and evolution of dual and offset agn in the astrid simulation at z 2 |
standard full-shape clustering analyses in fourier space rely on a fixed power spectrum template, defined at the fiducial cosmology used to convert redshifts into distances, and compress the cosmological information into the alcock-paczynski parameters and the linear growth rate of structure. in this paper, we propose an analysis method that operates directly in the cosmology parameter space and varies the power spectrum template accordingly at each tested point. predictions for the power spectrum multipoles from the tns model are computed at different cosmologies in the framework of $\lambda \rm {cdm}$. applied to the final eboss qso and lrg samples together with the low-z dr12 boss galaxy sample, our analysis results in a set of constraints on the cosmological parameters ωcdm, h0, σ8, ωb, and ns. to reduce the number of computed models, we construct an iterative process to sample the likelihood surface, where each iteration consists of a gaussian process regression. this method is validated with mocks from n-body simulations. from the combined analysis of the (e)boss data, we obtain the following constraints: σ8 = 0.877 ± 0.049 and $\omega _{\rm m}=0.304^{+0.016}_{-0.010}$ without any external prior. the eboss quasar sample alone shows a 3.1σ discrepancy compared to the planck prediction. | combined full shape analysis of boss galaxies and eboss quasars using an iterative emulator |
the recent discovery by cantalupo et al. of the largest (∼500 kpc) luminous (l ≃ 1.43 × 1045 erg s-1) lyα nebula associated with the quasar um287 (z = 2.279) poses a great challenge to our current understanding of the astrophysics of the halos hosting massive z ∼ 2 galaxies. either an enormous reservoir of cool gas is required m ≃ 1012 m⊙, exceeding the expected baryonic mass available, or one must invoke extreme gas clumping factors not present in high-resolution cosmological simulations. however, observations of lyα emission alone cannot distinguish between these two scenarios. we have obtained the deepest ever spectroscopic integrations in the he ii λ1640 and c iv λ1549 emission lines with the goal of detecting extended line emission, but detect neither line to a 3σ limiting sb ≃ 10-18 erg s-1 cm-2 arcsec-2. we construct simple models of the expected emission spectrum in the highly probable scenario that the nebula is powered by photoionization from the central hyper-luminous quasar. the non-detection of he ii implies that the nebular emission arises from a mass mc ≲ 6.4 × 1010 m⊙ of cool gas on ∼200 kpc scales, distributed in a population of remarkably dense (nh ≳ 3 cm-3) and compact (r ≲ 20 pc) clouds, which would clearly be unresolved by current cosmological simulations. given the large gas motions suggested by the lyα line (v ≃ 500 km s-1), it is unclear how these clouds survive without being disrupted by hydrodynamic instabilities. our work serves as a benchmark for future deep integrations with current and planned wide-field ifu spectrographs such as muse, kcwi, and kmos. our observations and models suggest that a ≃10 hr exposure would likely detect ∼10 rest-frame uv/optical emission lines, opening up the possibility of conducting detailed photoionization modeling to infer the physical state of gas in the circumgalactic medium. 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 the national aeronautics and space administration. the observatory was made possible by the generous financial support of the w.m. keck foundation. | deep he ii and c iv spectroscopy of a giant lyα nebula: dense compact gas clumps in the circumgalactic medium of a z ~ 2 quasar |
reverberation mapping technique (rm) is an important milestone that has elevated our understanding of active galactic nuclei (agn) demographics, giving information about the kinematics and the structure of the broad line region (blr). it is based on the time-delay response between the continuum and the emission line. the time delay is directly related to the size of the blr which in turn is related to the continuum luminosity of the source, producing the well-known radius-luminosity (rl) relation. the majority of the sources with rm data have been monitored for their hβ emission line in low redshift sources (z<0.1), while there are some attempts using the mgii line for higher redshift ranges. in this work, we present a recent mgii monitoring for the quasar cts c30.10 (z=0.90) observed with the 10-meter southern african large telescope (salt), for which the rl scaling based on mgii holds within measurement and time-delay uncertainties. one of the most important advantages of reverberation mapping technique is the independent determination to the distant source, and considering the large range of redshifts and luminosities found in agns their use in cosmological studies is promising. however, recently it has been found that highly accreting sources show the time delays shorter than expected from the rl relation. we have proposed a correction for this effect using a sample of 117 hβ reverberating-mapped agn with 0.02<z<0.9, which recovers the low scatter along with the relation. we are able to determine the cosmological constants, ω_m and ω_λ. despite the applied correction, the scatter is still large for being effective for cosmological applications. in the near future, large synoptic survey telescope (lsst) will cover over 10 million quasars in six photometric bands during its 10-year run. we present the first step in modelling of light curves for hβ and mgii and discuss the quasar selection in the context of photometric reverberation mapping with lsst. with the onset of the lsst era, we expect a huge rise in the overall quasar counts and redshift range covered (z≲7.0), which will provide a better constraint of agn properties with cosmological purposes. | current and future applications of reverberation-mapped quasars in cosmology |
we present a new empirical template for iron emission in active galactic nuclei (agns) covering the 4000-5600 å range. the new template is based on a spectrum of the narrow-line seyfert 1 galaxy mrk 493 obtained with the hubble space telescope. in comparison with the canonical iron template object i zw 1, mrk 493 has narrower broad-line widths, lower reddening, and a less extreme eddington ratio, making it a superior choice for template construction. we carried out a multicomponent spectral decomposition to produce a template incorporating all the permitted and forbidden lines of fe ii identified in the mrk 493 spectrum over this wavelength range, as well as lines from ti ii, ni ii, and cr ii. we tested the template by fitting it to agn spectra spanning a broad range of iron emission properties, and we present a detailed comparison with fits using other widely used monolithic and multicomponent iron emission templates. the new template generally provides the best fit (lowest χ 2) compared to other widely used monolithic empirical templates. in addition, the new template yields more accurate spectral measurements including a significantly better match of the derived balmer line profiles (hβ, hγ, hδ), in contrast with results obtained using the other templates. our comparison tests show that the choice of iron template can introduce a systematic bias in measurements of the hβ line width, which consequently impacts single-epoch black hole mass estimates by ~0.1 dex on average and possibly up to ~0.3-0.5 dex individually. * based on observations made with the nasa/esa hubble space telescope obtained from 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 go-14744. | a new iron emission template for active galactic nuclei. i. optical template for the hβ region |
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