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we present glade+, an extended version of the glade galaxy catalogue introduced in our previous paper for multimessenger searches with advanced gravitational-wave detectors. glade+ combines data from six separate but not independent astronomical catalogues: the gwgc, 2mpz, 2mass xsc, hyperleda, and wisexscospz galaxy catalogues, and the sdss-dr16q quasar catalogue. to allow corrections of cmb-frame redshifts for peculiar motions, we calculated peculiar velocities along with their standard deviations of all galaxies having b-band magnitude data within redshift z = 0.05 using the 'bayesian origin reconstruction from galaxies' formalism. glade+ is complete up to luminosity distance $d_l=47^{+4}_{-2}$ mpc in terms of the total expected b-band luminosity of galaxies, and contains all of the brightest galaxies giving 90 per cent of the total b-band and k-band luminosity up to dl ≃ 130 mpc. we include estimations of stellar masses and individual binary neutron star merger rates for galaxies with w1 magnitudes. these parameters can help in ranking galaxies in a given gravitational wave localization volume in terms of their likelihood of being hosts, thereby possibly reducing the number of pointings and total integration time needed to find the electromagnetic counterpart. | glade+ : an extended galaxy catalogue for multimessenger searches with advanced gravitational-wave detectors |
we present a comprehensive analysis of 21 light curves of type 1 active galactic nuclei (agn) from the kepler spacecraft. first, we describe the necessity and development of a customized pipeline for treating kepler data of stochastically variable sources like agn. we then present the light curves, power spectral density functions (psds), and flux histograms. the light curves display an astonishing variety of behaviors, many of which would not be detected in ground-based studies, including switching between distinct flux levels. six objects exhibit psd flattening at characteristic timescales that roughly correlate with black hole mass. these timescales are consistent with orbital timescales or free-fall accretion timescales. we check for correlations of variability and high-frequency psd slope with accretion rate, black hole mass, redshift, and luminosity. we find that bolometric luminosity is anticorrelated with both variability and steepness of the psd slope. we do not find evidence of the linear rms-flux relationships or lognormal flux distributions found in x-ray agn light curves, indicating that reprocessing is not a significant contributor to optical variability at the 0.1%-10% level. | the kepler light curves of agn: a detailed analysis |
with a projected size of about 450 kpc at z ≃ 2.3, the slug ly α nebula is a rare laboratory to study, in emission, the properties of the intergalactic gas in the cosmic web. since its discovery, the slug has been the subject of several spectroscopic follow-ups to constrain the properties of the emitting gas. here we report the results of a deep muse integral-field spectroscopic search for non-resonant, extended he ii λ 1640 and metal emission. extended he ii radiation is detected on scales of about 100 kpc, but only in some regions associated with the bright ly α emission and a continuum-detected source, implying large and abrupt variations in the line ratios across adjacent regions in projected space. the recent detection of associated h α emission and similar abrupt variations in the ly α kinematics, strongly suggest that the he ii/ly α gradient is due to large variations in the physical distances between the associated quasar and these regions. this implies that the overall length of the emitting structure could extend to physical mpc scales and be mostly oriented along our line of sight. at the same time, the relatively low he ii/ly α values suggest that the emitting gas has a broad density distribution that - if expressed in terms of a lognormal - implies dispersions as high as those expected in the interstellar medium of galaxies. these results strengthen the possibility that the density distribution of intergalactic gas at high redshift is extremely clumpy and multiphase on scales below our current observational spatial resolution of a few physical kpc. | the large- and small-scale properties of the intergalactic gas in the slug ly α nebula revealed by muse he ii emission observations |
we present the first model-agnostic analysis of the complete set of sloan digital sky survey iii (boss) and -iv (eboss) catalogues of luminous red galaxy and quasar clustering in the redshift range 0.2 ≤ z ≤ 2.2 (10 billion years of cosmic evolution), which consistently includes the baryon acoustic oscillations (bao), redshift space distortions (rsd) and the shape of the transfer function signatures, from pre- and post-reconstructed catalogues in fourier space. this approach complements the standard analyses techniques which only focus on the bao and rsd signatures, and the full-modeling approaches which assume a specific underlying cosmology model to perform the analysis. these model-independent results can then easily be interpreted in the context of the cosmological model of choice. in particular, when combined with z > 2.1 ly-α bao measurements, the clustering bao, rsd and shape parameters can be interpreted within a flat-λcdm model yielding h = 0.6816 ± 0.0067, ωm = 0.3001 ± 0.0057 and 109 × as = 2.43 ± 0.20 (or σ 8 = 0.858 ± 0.036) with a big bang nucleosynthesis prior on the baryon density. without any external dataset, the boss and eboss data alone imply ωm = 0.2971 ± 0.0061 and 109 × as = 2.39+0.24 -0.43 (or σ 8 = 0.857 ± 0.040). for models beyond λcdm, eboss data alone (in combination with planck) constrain the sum of neutrino mass to be σmν < 0.40 ev with a bbn prior (σmν < 0.082 ev) at 95% cl, the curvature energy density to ωk = -0.022+0.032 -0.038 (ωk = 0.0015 ± 0.0016) and the dark energy equation of state parameter to w = -0.998+0.085 -0.073 (w = -1.093+0.048 0.044) at 68% cl without a bbn prior. these results are the product of a substantial improvement of the state-of-the-art methodologies and represent the most precise model-agnostic cosmological constrains using spectroscopic large-scale data alone. | model-agnostic interpretation of 10 billion years of cosmic evolution traced by boss and eboss data |
the discovery of galaxies with regularly rotating discs at redshifts ≥4 has been a puzzling challenge to galaxy formation models that tend to predict chaotic gas kinematics in the early universe as a consequence of gas accretion, mergers, and efficient feedback. in this work, we investigated the kinematics of five highly resolved galaxies at z ~ 4.5 observed with alma in the [c ii] 158 $\mu$m emission line. the sample is diverse: aztec1 (starburst galaxy), bri1335-0417 (starburst and quasar host galaxy), j081740 (normal star-forming galaxy), and sgp38326 (two starburst galaxies in a group). the five galaxies show velocity gradients, but four were found to be rotating discs, while the remaining, aztec1, is likely a merger. we studied the gas kinematics of the discs using 3dbarolo and found that they rotate with maximum rotation velocities between 198 and 562 km s-1, while the gas velocity dispersions, averaged across the discs, are between 49 and 75 km s-1. the rotation curves are generally flat and the galaxies have ratios of ordered-to-random motion (v/σ) between 2.7 and 9.8. we present cannubi, an algorithm for fitting the disc geometry of rotating discs in 3d emission-line observations prior to modelling the kinematics, with which we find indications that these discs may have thicknesses of the order of 1 kpc. this study shows that early disc formation with a clear dominance of rotation with respect to turbulent motions is present across a variety of galaxy types. | regular rotation and low turbulence in a diverse sample of z 4.5 galaxies observed with alma |
we present a study of the metal-enriched cool halo gas traced by mg ii absorption around 228 galaxies at z ~ 0.8-1.5 within 28 quasar fields from the muse analysis of gas around galaxies survey. we observe no significant evolution in the mg ii equivalent width versus impact parameter relation and in the mg ii covering fraction compared to surveys at z ≲ 0.5. the stellar mass, along with distance from galaxy centre, appears to be the dominant factor influencing the mg ii absorption around galaxies. with a sample that is 90 per cent complete down to a star formation rate of ≈0.1 $\rm m_\odot yr^{-1}$ and up to impact parameters ≈250-350 kpc from quasars, we find that the majority ($67^{+12}_{-15}$ per cent or 14/21) of the mg ii absorption systems are associated with more than one galaxy. the complex distribution of metals in these richer environments adds substantial scatter to previously reported correlations. multiple galaxy associations show on average five times stronger absorption and three times higher covering fraction within twice the virial radius than isolated galaxies. the dependence of mg ii absorption on galaxy properties disfavours the scenario in which a widespread intragroup medium dominates the observed absorption. this leaves instead gravitational interactions among group members or hydrodynamic interactions of the galaxy haloes with the intragroup medium as favoured mechanisms to explain the observed enhancement in the mg ii absorption strength and cross-section in rich environments. | muse analysis of gas around galaxies (magg) - ii: metal-enriched halo gas around z ∼ 1 galaxies |
reverberation mapping (rm) measurements of broad-line region (blr) lags in z\gt 0.3 quasars are important for directly measuring black hole masses in these distant objects, but so far there have been limited attempts and success given the practical difficulties of rm in this regime. here we report preliminary results of 15 blr lag measurements from the sloan digital sky survey reverberation mapping (sdss-rm) project, a dedicated rm program with multi-object spectroscopy designed for rm over a wide redshift range. the lags are based on the 2014 spectroscopic light curves alone (32 epochs over six months) and focus on the hβ and mg ii broad lines in the 100 lowest-redshift (z\lt 0.8) quasars included in sdss-rm; they represent a small subset of the lags that sdss-rm (including 849 quasars to z∼ 4.5) is expected to deliver. the reported preliminary lag measurements are for intermediate-luminosity quasars at 0.3≲ z\lt 0.8, including nine hβ lags and six mg ii lags, for the first time extending rm results to this redshift-luminosity regime and providing direct quasar black hole mass estimates over approximately half of cosmic time. the mg ii lags also increase the number of known mg ii lags by several fold and start to explore the utility of mg ii for rm at high redshift. the location of these new lags at higher redshifts on the observed blr size-luminosity relationship is statistically consistent with previous hβ results at z\lt 0.3. however, an independent constraint on the relationship slope at z\gt 0.3 is not yet possible owing to the limitations in our current sample. our results demonstrate the general feasibility and potential of multi-object rm for z\gt 0.3 quasars. | the sloan digital sky survey reverberation mapping project: first broad-line hβ and mg ii lags at z ≳0.3 from six-month spectroscopy |
we perform a systematic search for long-term extreme variability quasars (evqs) in the overlapping sloan digital sky survey and 3 year dark energy survey imaging, which provide light curves spanning more than 15 years. we identified ∼1000 evqs with a maximum change in g-band magnitude of more than 1 mag over this period, about 10% of all quasars searched. the evqs have l bol ∼ 1045-1047 erg s-1 and l/l edd ∼ 0.01-1. accounting for selection effects, we estimate an intrinsic evq fraction of ∼30%-50% among all g≲ 22 quasars over a baseline of ∼15 yr. we performed detailed multi-wavelength, spectral, and variability analyses for the evqs and compared them to their parent quasar sample. we found that evqs are distinct from a control sample of quasars matched in redshift and optical luminosity: (1) their uv broad emission lines have larger equivalent widths; (2) their eddington ratios are systematically lower; and (3) they are more variable on all timescales. the intrinsic difference in quasar properties for evqs suggests that internal processes associated with accretion are the main driver for the observed extreme long-term variability. however, despite their different properties, evqs seem to be in the tail of a continuous distribution of quasar properties, rather than standing out as a distinct population. we speculate that evqs are normal quasars accreting at relatively low rates, where the accretion flow is more likely to experience instabilities that drive the changes in flux by a factor of a few on multi-year timescales. | extreme variability quasars from the sloan digital sky survey and the dark energy survey |
we present multiwavelength observations of the tidal disruption event (tde) iptf15af, discovered by the intermediate palomar transient factory survey at redshift z = 0.07897. the optical and ultraviolet (uv) light curves of the transient show a slow decay over 5 months, in agreement with previous optically discovered tdes. it also has a comparable blackbody peak luminosity of {l}peak}≈ 1.5× {10}44 {erg} {{{s}}}-1. the inferred temperature from the optical and uv data shows a value of (3-5) × 104 k. the transient is not detected in x-rays up to {l}{{x}}< 3× {10}42 {erg} {{{s}}}-1 within the first 5 months after discovery. the optical spectra exhibit two distinct broad emission lines in the he ii region, and at later times also hα emission. additionally, emission from [n iii] and [o iii] is detected, likely produced by the bowen fluorescence effect. uv spectra reveal broad emission and absorption lines associated with high-ionization states of n v, c iv, si iv, and possibly p v. these features, analogous to those of broad absorption line quasars (bal qsos), require an absorber with column densities {n}{{h}}> {10}23 cm-2. this optically thick gas would also explain the nondetection in soft x-rays. the profile of the absorption lines with the highest column density material at the largest velocity is opposite that of bal qsos. we suggest that radiation pressure generated by the tde flare at early times could have provided the initial acceleration mechanism for this gas. spectral uv line monitoring of future tdes could test this proposal. | the broad absorption line tidal disruption event iptf15af: optical and ultraviolet evolution |
we present a systematic search for periodically varying quasar and supermassive black hole binary (smbhb) candidates in the pan-starrs1 medium deep survey (mds). from ∼9000 color-selected quasars in an ∼50 °2 sky area, we initially identify 26 candidates with more than 1.5 cycles of variation. we extend the baseline of observations via our imaging campaign with the discovery channel telescope and the las cumbres observatory network and reevaluate the candidates using a more rigorous, maximum likelihood method. using a range of statistical criteria and assuming the damped random walk model for normal quasar variability, we identify one statistically significant periodic candidate. we also investigate the capabilities of detecting smbhbs with the large synoptic survey telescope using our study with mds as a benchmark and explore any complementary multiwavelength evidence for smbhbs in our sample. | supermassive black hole binary candidates from the pan-starrs1 medium deep survey |
the relationship between quasars and their host galaxies provides clues on how supermassive black holes (smbhs) and massive galaxies are jointly assembled. to elucidate this connection, we measure the structural and photometric properties of the host galaxies of ~5000 sloan digital sky survey quasars at 0.2 < z < 1 using five-band (grizy) optical imaging from the hyper suprime-cam subaru strategic program. an automated analysis tool is used to forward-model the blended emission of the quasar as characterized by the point-spread function and the underlying host galaxy as a two-dimensional sérsic profile. we find that quasars are preferentially hosted by massive star-forming galaxies with disklike light profiles. furthermore, the size distribution of quasar hosts is broad at a given stellar mass and the average values exhibit a size-stellar mass relation as seen with inactive galaxies. in contrast, the sizes of quasar hosts are more compact than those of inactive star-forming galaxies on average, but not as compact as those of quiescent galaxies of similar stellar masses. this is true irrespective of quasar properties, including the bolometric luminosity, eddington ratio, and black hole mass. these results are consistent with a scenario in which galaxies are concurrently fueling an smbh and building their stellar bulge from a centrally concentrated gas reservoir. alternatively, quasar hosts may be experiencing a compaction process in which stars from the disk and inflowing gas are responsible for growing the bulge. in addition, we confirm that the host galaxies of type 1 quasars have a bias of being closer to face-on systems, suggesting that galactic-scale dust can contribute to obscuring the broad-line region. | the sizes of quasar host galaxies in the hyper suprime-cam subaru strategic program |
we present the discovery and spectroscopic confirmation with the european southern observatory new technology telescope (ntt) and gemini south telescopes of eight new, and the rediscovery of two previously known, 6.0 < z < 6.5 quasars with zab < 21.0. these quasars were photometrically selected without any morphological criteria from 1533 deg2 using spectral energy distribution (sed) model fitting to photometric data from dark energy survey (g, r, i, z, y), vista hemisphere survey (j, h, k) and wide-field infrared survey explorer (w1, w2). the photometric data were fitted with a grid of quasar model seds with redshift-dependent ly α forest absorption and a range of intrinsic reddening as well as a series of low-mass cool star models. candidates were ranked using an sed-model-based χ2-statistic, which is extendable to other future imaging surveys (e.g. lsst and euclid). our spectral confirmation success rate is 100 per cent without the need for follow-up photometric observations as used in other studies of this type. combined with automatic removal of the main types of non-astrophysical contaminants, the method allows large data sets to be processed without human intervention and without being overrun by spurious false candidates. we also present a robust parametric redshift estimator that gives comparable accuracy to mg ii and co-based redshift estimators. we find two z ∼ 6.2 quasars with h ii near zone sizes ≤3 proper mpc that could indicate that these quasars may be young with ages ≲ 106-107 years or lie in over dense regions of the igm. the z = 6.5 quasar vdes j0224-4711 has jab = 19.75 and is the second most luminous quasar known with z ≥ 6.5. | eight new luminous z ≥ 6 quasars discovered via sed model fitting of vista, wise and dark energy survey year 1 observations |
in this letter, we present a cosmic bell experiment with polarization-entangled photons, in which measurement settings were determined based on real-time measurements of the wavelength of photons from high-redshift quasars, whose light was emitted billions of years ago; the experiment simultaneously ensures locality. assuming fair sampling for all detected photons and that the wavelength of the quasar photons had not been selectively altered or previewed between emission and detection, we observe statistically significant violation of bell's inequality by 9.3 standard deviations, corresponding to an estimated p value of ≲7.4 ×10-21. this experiment pushes back to at least ∼7.8 gyr ago the most recent time by which any local-realist influences could have exploited the "freedom-of-choice" loophole to engineer the observed bell violation, excluding any such mechanism from 96% of the space-time volume of the past light cone of our experiment, extending from the big bang to today. | cosmic bell test using random measurement settings from high-redshift quasars |
ss 433 is a binary system containing a supergiant star that is overflowing its roche lobe with matter accreting onto a compact object (either a black hole or neutron star)1-3. two jets of ionized matter with a bulk velocity of approximately 0.26c (where c is the speed of light in vacuum) extend from the binary, perpendicular to the line of sight, and terminate inside w50, a supernova remnant that is being distorted by the jets2,4-8. ss 433 differs from other microquasars (small-scale versions of quasars that are present within our own galaxy) in that the accretion is believed to be super-eddington9-11, and the luminosity of the system is about 1040 ergs per second2,9,12,13. the lobes of w50 in which the jets terminate, about 40 parsecs from the central source, are expected to accelerate charged particles, and indeed radio and x-ray emission consistent with electron synchrotron emission in a magnetic field have been observed14-16. at higher energies (greater than 100 gigaelectronvolts), the particle fluxes of γ-rays from x-ray hotspots around ss 433 have been reported as flux upper limits6,17-20. in this energy regime, it has been unclear whether the emission is dominated by electrons that are interacting with photons from the cosmic microwave background through inverse-compton scattering or by protons that are interacting with the ambient gas. here we report teraelectronvolt γ-ray observations of the ss 433/w50 system that spatially resolve the lobes. the teraelectronvolt emission is localized to structures in the lobes, far from the centre of the system where the jets are formed. we have measured photon energies of at least 25 teraelectronvolts, and these are certainly not doppler-boosted, because of the viewing geometry. we conclude that the emission—from radio to teraelectronvolt energies—is consistent with a single population of electrons with energies extending to at least hundreds of teraelectronvolts in a magnetic field of about 16 microgauss. | very-high-energy particle acceleration powered by the jets of the microquasar ss 433 |
we study the link between galaxies and h i-selected absorption systems at z ~ 3-4 in the muse analysis of gas around galaxies (magg) survey, an eso large programme consisting of integral field spectroscopic observations of 28 quasar fields hosting 61 strong absorbers with $\rm n_{\rm h\,{\small i}}\gtrsim 10^{16.5}~\rm cm^{-2}$. we identify 127 ly α emitting galaxies (laes) around the absorbers, corresponding to a detection rate of 82 ± 16 per cent. the luminosity function of these laes is ≈5 times higher in normalization than the field population and we detect a significant clustering of galaxies with respect to the gas, confirming that high column density absorbers and laes trace each other. between 30 and 40 per cent of the absorbers are associated with multiple laes, which lie preferentially along filaments. galaxies in groups also exhibit a three times higher covering factor of optically thick gas compared to isolated systems. no significant correlations are identified between the emission properties of laes and the absorption properties of optically thick gas clouds, except for a weak preference of brighter and multiple galaxies to reside near broad absorbers. based on the measured impact parameters and the covering factor, we conclude that the near totality of optically thick gas in the universe can be found in the outer circumgalactic medium (cgm) of laes or in the intergalactic medium (igm) in proximity to these galaxies. thus, laes act as tracers of larger scale structures within which both galaxies and optically thick clouds are embedded. the patchy and inhomogeneous nature of the cgm and igm explains the lack of correlations between absorption and emission properties. this implies that very large samples are needed to unveil the trends that encode the properties of the baryon cycle. | muse analysis of gas around galaxies (magg) - iv. the gaseous environment of z 3-4 ly α emitting galaxies |
we analyse the full shape of anisotropic clustering measurements from the extended baryon oscillation spectroscopic survey quasar sample together with the combined galaxy sample from the baryon oscillation spectroscopic survey. we obtain constraints on the cosmological parameters independent of the hubble parameter h for the extensions of the lambda cold dark matter (λcdm) models, focusing on cosmologies with free dark energy equation of state parameter w. we combine the clustering constraints with those from the latest cosmic microwave background data from planck to obtain joint constraints for these cosmologies for w and the additional extension parameters - its time evolution wa, the physical curvature density ωk and the neutrino mass sum ∑mν. our joint constraints are consistent with a flat λcdm cosmological model within 68 per cent confidence limits. we demonstrate that the planck data are able to place tight constraints on the clustering amplitude today, σ12, in cosmologies with varying w and present the first constraints for the clustering amplitude for such cosmologies, which is found to be slightly higher than the λcdm value. additionally, we show that when we vary w and allow for non-flat cosmologies and the physical curvature density is used, planck prefers a curved universe at 4σ significance, which is ~2σ higher than when using the relative curvature density ωk. finally, when w is varied freely, clustering provides only a modest improvement (of 0.021 ev) on the upper limit of ∑mν. | beyond - λcdm constraints from the full shape clustering measurements from boss and eboss |
multiply imaged time-variable sources can be used to measure absolute distances as a function of redshifts and thus determine cosmological parameters, chiefly the hubble constant h0. in the two decades up to 2020, through a number of observational and conceptual breakthroughs, this so-called time-delay cosmography has reached a precision sufficient to be an important independent voice in the current "hubble tension" debate between early- and late-universe determinations of h0. the 2020s promise to deliver major advances in time-delay cosmography, owing to the large number of lenses to be discovered by new and upcoming surveys and the vastly improved capabilities for follow-up and analysis. in this review, after a brief summary of the foundations of the method and recent advances, we outline the opportunities for the decade and the challenges that will need to be overcome in order to meet the goal of the determination of h0 from time-delay cosmography with 1% precision and accuracy. | strong lensing time-delay cosmography in the 2020s |
the bulk of the x-ray emission in active galactic nuclei (agns) is produced very close to the accreting supermassive black hole (smbh), in a corona of hot electrons which up scatters optical and ultraviolet photons from the accretion flow. the cut-off energy (ec) of the primary x-ray continuum emission carries important information on the physical characteristics of the x-ray emitting plasma, but little is currently known about its potential relation with the properties of accreting smbhs. using the largest broad-band (0.3-150 kev) x-ray spectroscopic study available to date, we investigate how the corona is related to the agn luminosity, black hole mass and eddington ratio (λedd). assuming a slab corona the median values of the temperature and optical depth of the comptonizing plasma are kte = 105 ± 18 kev and τ = 0.25 ± 0.06, respectively. when we properly account for the large number of ec lower limits, we find a statistically significant dependence of the cut-off energy on the eddington ratio. in particular, objects with λedd > 0.1 have a significantly lower median cut-off energy (ec = 160 ± 41 kev) than those with λedd ≤ 0.1 (ec = 370 ± 51 kev). this is consistent with the idea that radiatively compact coronae are also cooler, because they tend to avoid the region in the temperature-compactness parameter space where runaway pair production would dominate. we show that this behaviour could also straightforwardly explain the suggested positive correlation between the photon index (γ) and the eddington ratio, being able to reproduce the observed slope of the γ-λedd trend. | bat agn spectroscopic survey - xii. the relation between coronal properties of active galactic nuclei and the eddington ratio |
we report the results from a search for z > 6.5 quasars using the dark energy survey (des) year 3 data set combined with the vista hemisphere survey (vhs) and wise all-sky survey. our photometric selection method is shown to be highly efficient in identifying clean samples of high-redshift quasars, leading to spectroscopic confirmation of three new quasars - vdes j0244-5008 (z = 6.724), vdes j0020-3653 (z = 6.834), and vdes j0246-5219 (z = 6.90) - which were selected as the highest priority candidates in the survey data without any need for additional follow-up observations. we have obtained spectroscopic observations in the near-infrared for vdes j0244-5008 and vdes j0020-3653 as well as our previously identified quasar, vdes j0224-4711 at z = 6.50 from reed et al. we use the near-infrared spectra to derive virial black hole masses from the full width at half-maximum of the mg ii line. these black hole masses are ≃1-2 × 109 m⊙. combined with the bolometric luminosities of these quasars of lbol ≃ 1-3 × 1047, these imply that the eddington ratios are high, ≃0.6-1.1. we consider the c iv emission line properties of the sample and demonstrate that our high-redshift quasars do not have unusual c iv line properties when compared to carefully matched low-redshift samples. our new des + vhs z > 6.5 quasars now add to the growing census of luminous, rapidly accreting supermassive black holes seen well into the epoch of reionization. | three new vhs-des quasars at 6.7 < z < 6.9 and emission line properties at z > 6.5 |
we present cosmological radiation-hydrodynamic simulations, performed with the code ramses-rt, of radiatively-driven outflows in a massive quasar host halo at z = 6. our simulations include both single- and multiscattered radiation pressure on dust from a quasar and are compared against simulations performed with thermal feedback. for radiation pressure-driving, we show that there is a critical quasar luminosity above which a galactic outflow is launched, set by the equilibrium of gravitational and radiation forces. while this critical luminosity is unrealistically high in the single-scattering limit for plausible black hole masses, it is in line with a {≈ } 3 × 10^9 m_⊙ black hole accreting at its eddington limit, if infrared (ir) multiscattering radiation pressure is included. the outflows are fast (v ≳ 1000 km s^{-1}) and strongly mass-loaded with peak mass outflow rates {≈ } 10^3-10^4 m_⊙ yr^{-1}, but short-lived ({<} 10 myr). outflowing material is multiphase, though predominantly composed of cool gas, forming via a thermal instability in the shocked swept-up component. radiation pressure- and thermally-driven outflows both affect their host galaxies significantly, but in different, complementary ways. thermally-driven outflows couple more efficiently to diffuse halo gas, generating more powerful, hotter, and more volume-filling outflows. ir radiation, through its ability to penetrate dense gas via diffusion, is more efficient at ejecting gas from the bulge. the combination of gas ejection through outflows with internal pressurization by trapped ir radiation leads to a complete shut down of star formation in the bulge. we hence argue that radiation pressure-driven feedback may be an important ingredient in regulating star formation in compact starbursts, especially during the quasar's `obscured' phase. | quenching star formation with quasar outflows launched by trapped ir radiation |
we present a catalog of central engine properties, i.e., black hole mass (mbh) and accretion luminosity (ldisk), for a sample of 1077 blazars detected with the fermi large area telescope. this includes broad emission-line systems and blazars whose optical spectra lack emission lines but are dominated by the absorption features arising from the host galaxy. the average mbh for the sample is $\langle \mathrm{log}\,{m}_{\mathrm{bh},\mathrm{all}{m}_{\odot }}\rangle =8.60$ <!-- --> , and there is evidence suggesting the association of more massive black holes with absorption-line systems. our results indicate a bimodality of ldisk in eddington units (ldisk/ledd) with broad-line objects tend to have a higher accretion rate (ldisk/ledd > 0.01). we have found that ldisk/ledd and compton dominance (cd; the ratio of the inverse compton to synchrotron peak luminosities) are positively correlated at the >5σ confidence level, suggesting that the latter can be used to reveal the state of accretion in blazars. based on this result, we propose a cd-based classification scheme. sources with cd > 1 can be classified as high-compton-dominated or hcd blazars, whereas those with cd ≲ 1 are low-compton-dominated (lcd) objects. this scheme is analogous to that based on the mass accretion rate proposed in the literature; however, it overcomes the limitation imposed by the difficulty in measuring ldisk and mbh for objects with quasi-featureless spectra. we conclude that the overall physical properties of fermi blazars are likely to be controlled by the accretion rate in eddington units. the catalog is made public at http://www.ucm.es/blazars/engines and zenodo. | the central engines of fermi blazars |
we present the spectroscopic discovery of 69 quasars at 5.8 < z < 7.0, drawn from the hyper suprime-cam (hsc) subaru strategic program (ssp) imaging survey data. this is the 16th publication from the subaru high-z exploration of low-luminosity quasars (shellqs) project, and it completes identification of all but the faintest candidates (i.e., i-band dropouts with z ab < 24 and y-band detections, and z-band dropouts with y ab < 24) with bayesian quasar probability ${p}_{q}^{b}\gt 0.1$ in the hsc-ssp third public data release (pdr3). the sample reported here also includes three quasars with ${p}_{q}^{b}\lt 0.1$ at z ~ 6.6, which we selected in an effort to completely cover the reddest point sources with simple color cuts. the number of high-z quasars discovered in shellqs has now grown to 162, including 23 type ii quasar candidates. this paper also presents identification of seven galaxies at 5.6 < z < 6.7, an [o iii] emitter at z = 0.954, and 31 galactic cool stars and brown dwarfs. high-z quasars and galaxies compose 75% and 16%, respectively, of all the spectroscopic shellqs objects that pass our latest selection algorithm with the pdr3 photometry. that is, a total of 91% of the objects lie at z > 5.6. this demonstrates that the algorithm has very high efficiency, even though we are probing an unprecedentedly low luminosity population down to m 1450 ~ -21 mag. | subaru high-z exploration of low-luminosity quasars (shellqs). xvi. 69 new quasars at 5.8 < z < 7.0 |
we characterize the stellar mass of j2239+0207, a z ~ 6.25 sub-eddington quasar (m 1450 = -24.6), using dedicated jwst/nircam medium-band observations of a nearby point-spread function star to remove the central point source and reveal the underlying galaxy emission. we detect the host galaxy in two bands longward of the balmer break, obtaining a stellar mass of ~1010 m ⊙, more than an order of magnitude less than this quasar's existing measured [c ii] dynamical mass. we additionally calculate the mass of j2239+0207's central supermassive black hole using jwst/nirspec integral field unit observations, and determine that the black hole is ~15 times more massive than predicted by the local m bh-m * relation, similar to many high-redshift quasars with dynamical masses determined via millimeter-wave line widths. we carefully consider potential selection effects at play, and find that even when z ~ 6 quasars are compared to a local sample with similarly determined dynamical masses, many of the high-redshift quasars appear to possess overmassive black holes. we conclude z ~ 6 quasars are likely to have a larger spread about the m bh-m * relation than observed in the local universe. | detection of the low-stellar-mass host galaxy of a z 6.25 quasar with jwst |
recent observations suggest that there are violations of the isotropy of the universe at large scales, which is an important part of the cosmological principle. in this paper, we use the cosmic microwave background (cmb) data to search for spatial variations of the cosmological parameters in the λ cdm model. we fit the planck temperature angular power spectrum cℓtt for 48 different half-skies, centering on 48 different directions, to search for directional dependences of the standard cosmological parameters. there are 3 [2 ]σ -level directional variations in ωbh2, ωch2, ns, 100 θmc, and h0 [τ and ln (1010as)]. furthermore, the directional distributions of the parameters follow a dipole form to good approximation. the bayes factor between the isotropic and anisotropic hypotheses is 0.0041, strongly disfavoring the former. the best-fit dipole axes for ωbh2, ωch2, ns, 100 θmc, and ase-2 τ all generally align with the mean direction of v ≡(l =48.8-14.4+14.3° ,b =-5.6-17.4+17.0° ) , which is roughly perpendicular to the dipole of the variation in the fine-structure constant, and is about 45° to the directions of the cmb kinematic dipole, cmb parity asymmetry, and polarization of quasars. our results suggest either a significant violation of the cosmological principle, or previously unknown systematic errors in the standard cmb analysis. | directional variations of cosmological parameters from the planck cmb data |
supermassive primordial stars are suspected to be the progenitors of the most massive quasars at z ∼ 6. previous studies of such stars were either unable to resolve hydrodynamical timescales or considered stars in isolation, not in the extreme accretion flows in which they actually form. therefore, they could not self-consistently predict their final masses at collapse, or those of the resulting supermassive black hole seeds, but rather invoked comparison to simple polytropic models. here, we systematically examine the birth, evolution, and collapse of accreting, non-rotating supermassive stars under accretion rates of 0.01-10 m ⊙ yr-1 using the stellar evolution code kepler. our approach includes post-newtonian corrections to the stellar structure and an adaptive nuclear network and can transition to following the hydrodynamic evolution of supermassive stars after they encounter the general relativistic instability. we find that this instability triggers the collapse of the star at masses of 150,000-330,000 m ⊙ for accretion rates of 0.1-10 m ⊙ yr-1, and that the final mass of the star scales roughly logarithmically with the rate. the structure of the star, and thus its stability against collapse, is sensitive to the treatment of convection and the heat content of the outer accreted envelope. comparison with other codes suggests differences here may lead to small deviations in the evolutionary state of the star as a function of time, that worsen with accretion rate. since the general relativistic instability leads to the immediate death of these stars, our models place an upper limit on the masses of the first quasars at birth. | on the maximum mass of accreting primordial supermassive stars |
we present observations of 50 pairs of redshift z ≈ 0.2 star-forming galaxies and background quasars. these sightlines probe the circumgalactic medium (cgm) out to half the virial radius, and we describe the circumgalactic gas kinematics relative to the reference frame defined by the galactic disks. we detect halo gas in mg ii absorption, measure the equivalent-width-weighted doppler shifts relative to each galaxy, and find that the cgm has a component of angular momentum that is aligned with the galactic disk. no net counter-rotation of the cgm is detected within 45° of the major axis at any impact parameter. the velocity offset of the circumgalactic gas correlates with the projected rotation speed in the disk plane out to disk radii of roughly 70 kpc. we confirm previous claims that the mg ii absorption becomes stronger near the galactic minor axis, and we show that the equivalent width correlates with the velocity range of the absorption. we cannot directly measure the location of any absorber along the sightline, but we explore the hypothesis that individual velocity components can be associated with gas orbiting in the disk plane or flowing radially outward in a conical outflow. we conclude that centrifugal forces partially support the low-ionization gas and galactic outflows kinematically disturb the cgm producing excess absorption. our results firmly rule out schema for the inner cgm that lack rotation and suggest that angular momentum as well as galactic winds should be included in any viable model for the low-redshift cgm. | kinematics of circumgalactic gas: feeding galaxies and feedback |
strong gravitational lensing provides a powerful probe of the physical properties of quasars and their host galaxies. a high fraction of the most luminous high-redshift quasars was predicted to be lensed due to magnification bias. however, no multiple imaged quasar was found at z > 5 in previous surveys. we report the discovery of j043947.08+163415.7, a strongly lensed quasar at z = 6.51, the first such object detected at the epoch of reionization, and the brightest quasar yet known at z > 5. high-resolution hubble space telescope imaging reveals a multiple imaged system with a maximum image separation θ ∼ 0.″2, best explained by a model of three quasar images lensed by a low-luminosity galaxy at z ∼ 0.7, with a magnification factor of ∼50. the existence of this source suggests that a significant population of strongly lensed, high-redshift quasars could have been missed by previous surveys, as standard color selection techniques would fail when the quasar color is contaminated by the lensing galaxy. | the discovery of a gravitationally lensed quasar at z = 6.51 |
we present alma [c ii] line and far-infrared (fir) continuum observations of three z > 6 low-luminosity quasars (m_1450 > -25 mag) discovered by our subaru hyper suprime-cam (hsc) survey. the [c ii] line was detected in all three targets with luminosities of (2.4-9.5) × 10^8 l_{⊙}, about one order of magnitude smaller than optically luminous (m_1450 ≲ -25 mag) quasars. the fir continuum luminosities range from < 9 × 10^{10} l_{⊙} (3 σ limit) to {∼ } 2 × 10^{12} l_{⊙}, indicating a wide range in star formation rates in these galaxies. most of the hsc quasars studied thus far show [c ii]/ fir luminosity ratios similar to local star-forming galaxies. using the [c ii]-based dynamical mass (m_dyn) as a surrogate for bulge stellar mass (m_{ bulge}), we find that a significant fraction of low-luminosity quasars are located on or even below the local m_{ bh}-m_{ bulge} relation, particularly at the massive end of the galaxy mass distribution. in contrast, previous studies of optically luminous quasars have found that black holes are overmassive relative to the local relation. given the low luminosities of our targets, we are exploring the nature of the early co-evolution of supermassive black holes and their hosts in a less biased way. almost all of the quasars presented in this work are growing their black hole mass at a much higher pace at z ∼ 6 than the parallel growth model, in which supermassive black holes and their hosts grow simultaneously to match the local m_{ bh}-m_{ bulge} relation at all redshifts. as the low-luminosity quasars appear to realize the local co-evolutionary relation even at z ∼ 6, they should have experienced vigorous starbursts prior to the currently observed quasar phase to catch up with the relation. | subaru high-z exploration of low-luminosity quasars (shellqs). viii. a less biased view of the early co-evolution of black holes and host galaxies |
we use higher redshift gamma-ray burst (grb), h ii starburst galaxy (h iig), and quasar angular size (qso-as) measurements to constrain six spatially flat and non-flat cosmological models. these three sets of cosmological constraints are mutually consistent. cosmological constraints from a joint analysis of these data sets are largely consistent with currently accelerating cosmological expansion and with cosmological constraints derived from a combined analysis of hubble parameter (h(z)) and baryon acoustic oscillation (bao, with planck-determined baryonic matter density) measurements. a joint analysis of the h(z) + bao + qso-as + h iig + grb data provides fairly model-independent determinations of the non-relativistic matter density parameter $\omega _{\rm m_0}=0.313\pm 0.013$ and the hubble constant $h_0=69.3\pm 1.2\, \rm {km \, s^{-1} \, mpc^{-1}}$. these data are consistent with the dark energy being a cosmological constant and with spatial hypersurfaces being flat, but they do not rule out mild dark energy dynamics or a little spatial curvature. we also investigate the effect of including quasar flux measurements in the mix and find no novel conclusions. | cosmological constraints from higher redshift gamma-ray burst, h ii starburst galaxy, and quasar (and other) data |
we report the discovery and analysis of the most metal-poor damped lyα (dla) system currently known, which also displays the lyman series absorption lines of neutral deuterium. the average [o/h] abundance of this system is [o/h] = -2.804 ± 0.015, which includes an absorption component with [o/h] = -3.07 ± 0.03. despite the unfortunate blending of many weak d i absorption lines, we report a precise measurement of the deuterium abundance of this system. using the six highest-quality and self-consistently analyzed measures of d/h in dlas, we report tentative evidence for a subtle decrease of d/h with increasing metallicity. this trend must be confirmed with future high-precision d/h measurements spanning a range of metallicity. a weighted mean of these six independent measures provides our best estimate of the primordial abundance of deuterium, 105 (d/h)p = 2.547 ± 0.033 ({{log}}10 {{{(d/h)}}}{{p}}=-4.5940+/- 0.0056). we perform a series of detailed monte carlo calculations of big bang nucleosynthesis (bbn) that incorporate the latest determinations of several key nuclear reaction cross-sections, and propagate their associated uncertainty. combining our measurement of (d/h)p with these bbn calculations yields an estimate of the cosmic baryon density, 100 ωb,0 h 2(bbn) = 2.156 ± 0.020, if we adopt the most recent theoretical determination of the d{(p,γ )}3{he} reaction rate. this measure of ωb,0 h 2 differs by ∼2.3σ from the standard model value estimated from the planck observations of the cosmic microwave background. using instead a d{(p,γ )}3{he} reaction rate that is based on the best available experimental cross-section data, we estimate 100 ωb,0 h 2(bbn) = 2.260 ± 0.034, which is in somewhat better agreement with the planck value. forthcoming measurements of the crucial d{(p,γ )}3{he} cross-section may shed further light on this discrepancy. based on observations collected at the european organisation for astronomical research in the southern hemisphere, chile (vlt program id: 093.a-0016(a)), and 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. | the primordial deuterium abundance of the most metal-poor damped lyman-α system |
in this work, we obtain measurements of the hubble constant in the context of modified gravity theories. we set up our theoretical framework by considering viable cosmological f (r ) and f (t ) models, and we analyzed them through the use of geometrical datasets obtained in a model-independent way, namely, gravitationally lensed quasars with measured time delays, standard clocks from cosmic chronometers, and standard candles from the pantheon supernovae ia sample. we find h0=(72.4 ±1.4 ) km s-1 mpc-1 and h0=(71.5 ±1.3 ) km s-1 mpc-1 for the f (r ) and f (t ) models, respectively. our results represent 1.9% and 1.8% measurements of the hubble constant, which are fully consistent with the local estimate of h0 by the hubble space telescope. we do not find significant departures from general relativity, as our study shows that the characteristic parameters of the extensions of gravity beyond general relativity are compatible with the λ cdm cosmology. moreover, within the standard cosmological framework, our full joint analysis suggests that it is possible to measure the dark energy equation of state parameter at 1.2% accuracy, although we find no statistical evidence for deviations from the cosmological constant case. | measurements of h0 in modified gravity theories: the role of lensed quasars in the late-time universe |
direct collapse black hole (dcbh) formation with mass ≳105 m⊙ is a promising scenario for the origin of high-redshift supermassive black holes. it has usually been supposed that the dcbh can only form in the primordial gas since the metal enrichment enhances the cooling ability and causes the fragmentation into smaller pieces. what actually happens in such an environment, however, has not been explored in detail. here, we study the impact of the metal enrichment on the clouds, conducting hydrodynamical simulations to follow the cloud evolution in cases with different degree of the metal enrichment z/z⊙ = 10-6 to 10-3. below z/z⊙ = 10-6, metallicity has no effect and supermassive stars form along with a small number of low-mass stars. with more metallicity $z/\mathrm{ z}_{\odot } \gtrsim5 \times 10^{-6}$, although the dust cooling indeed promotes fragmentation of the cloud core and produces about a few thousand low-mass stars, the accreting flow preferentially feeds the gas to the central massive stars, which grows supermassive as in the primordial case. we term this formation mode as the super competitive accretion, where only the central few stars grow supermassive while a large number of other stars are competing for the gas reservoir. once the metallicity exceeds 10-3 z⊙ and metal-line cooling becomes operative, the central star cannot grow supermassive due to lowered accretion rate. supermassive star formation by the super competitive accretion opens up a new window for seed bhs, which relaxes the condition on metallicity and enhances the seed bh abundance. | supermassive star formation via super competitive accretion in slightly metal-enriched clouds |
recent breakthroughs of pretrained language models have shown the effectiveness of self-supervised learning for a wide range of natural language processing (nlp) tasks. in addition to standard syntactic and semantic nlp tasks, pretrained models achieve strong improvements on tasks that involve real-world knowledge, suggesting that large-scale language modeling could be an implicit method to capture knowledge. in this work, we further investigate the extent to which pretrained models such as bert capture knowledge using a zero-shot fact completion task. moreover, we propose a simple yet effective weakly supervised pretraining objective, which explicitly forces the model to incorporate knowledge about real-world entities. models trained with our new objective yield significant improvements on the fact completion task. when applied to downstream tasks, our model consistently outperforms bert on four entity-related question answering datasets (i.e., webquestions, triviaqa, searchqa and quasar-t) with an average 2.7 f1 improvements and a standard fine-grained entity typing dataset (i.e., figer) with 5.7 accuracy gains. | pretrained encyclopedia: weakly supervised knowledge-pretrained language model |
cosmic reionization holds the key to understand structure formation in the universe, and can inform us about the properties of the first sources, as their star formation efficiency and escape fraction of ionizing photons. by combining the recent release of planck electron scattering optical depth data with observations of high-redshift quasar absorption spectra, we obtain strong constraints on viable reionization histories. we show that inclusion of planck data favors a reionization scenario with a single stellar population. the mean xh i drops from ∼0.8 at z = 10.6 to ∼10-4 at z = 5.8 and reionization is completed around 5.8 ≲ z ≲ 8.5 (2σ), thus indicating a significant reduction in contributions to reionization from high-redshift sources. we can put independent constraints on the escape fraction fesc of ionizing photons by incorporating the high-redshift galaxy luminosity function data into our analysis. we find a non-evolving fesc of ∼10 per cent in the redshift range z = 6-9. | cosmic reionization after planck. |
context. the existence of tight correlations between supermassive black holes (bhs) and their host galaxies' properties in the local universe suggests a closely linked evolution. investigating these relations up to the high redshifts (z ≳ 6) is crucial in order to understand the interplay between star formation and bh growth across the cosmic time and to set constraints on galaxy formation and evolution models. in this work, we focus on the relation between bh mass (mbh) and the dynamical mass (mdyn) of the host galaxy.aims: previous works suggest an evolution of the mbh-mdyn relation with redshift indicating that bh growth precedes the galaxy mass assembly during their co-evolution at z > 3. however, dynamical galaxy masses at high redshift are often estimated through the virial theorem, thus introducing significant uncertainties. within the scope of this work, our aim is to study the mbh-mdyn relation of a sample of 2 < z < 7 quasars by constraining their galaxy masses through a full kinematical modelling of the cold gas kinematics, thus avoiding all possible biases and effects introduced by the rough estimates usually adopted so far.methods: for this purpose, we retrieved public observations of 72 quasar host galaxies observed in [cii]158 μm or co transitions with the atacama large millimeter array (alma). we then selected those quasars whose line emission is spatially resolved, and performed a kinematic analysis on alma observations. we estimated the dynamical mass of the systems by modelling the gas kinematics with a rotating disc, taking into account geometrical and instrumental effects. our dynamical mass estimates, combined with mbh obtained from literature and our own new civλ1550 observations allowed us to investigate the mbh/mdyn in the early universe.results: overall, we obtained a sample of ten quasars at z ∼ 2-7, in which line emission is detected with high s/n (≳5-10) and the gas kinematics are spatially resolved and dominated by ordered rotation. the estimated dynamical masses place six out of ten quasars above the local relation yielding to mbh/mdyn ratios ∼10× higher than those estimated in low-z galaxies. on the other hand, we found that four quasars at z ∼ 4-6 have dynamical-to-bh-mass ratios consistent with what is observed in early-type galaxies in the local universe. | the alma view of the high-redshift relation between supermassive black holes and their host galaxies |
recent studies have revealed intense ultraviolet (uv) metal emission lines in a modest sample of z > 7 lyman-α emitters, indicating a hard ionizing spectrum is present. if such high ionization features are shown to be common, it may indicate that extreme radiation fields play a role in regulating the visibility of lyα in the reionization era. here, we present deep near-infrared spectra of seven galaxies with lyα emission at 5.4 < z < 8.7 (including a newly confirmed lensed galaxy at zlyα = 6.031) and three bright z ≃ 7 photometric targets. in nine sources, we do not detect uv metal lines. however in the zlyα = 8.683 galaxy egsy8p7, we detect a 4.6σ emission line in the narrow spectral window expected for n vλ1243. the feature is unresolved (fwhm < 90 km s-1) and is likely nebular in origin. a deep h-band spectrum of egsy8p7 reveals non-detections of c iv, he ii, and o iii]. the presence of n v requires a substantial flux of photons above 77 ev, pointing to a hard ionizing spectrum powered by an active galactic nucleus or fast radiative shocks. regardless of its origin, the intense radiation field of egsy8p7 may aid the transmission of lyα through what is likely a partially neutral intergalactic medium. with this new detection, five of 13 known lyα emitters at z > 7 have now been shown to have intense uv line emission, suggesting that extreme radiation fields are commonplace among the lyα population. future observations with jwst will eventually clarify the origin of these features and explain their role in the visibility of lyα in the reionization era. | spectroscopic constraints on uv metal line emission at z ≃ 6-9: the nature of lyα emitting galaxies in the reionization era |
we present atacama large millimeter array 1 mm observations of the rest-frame far-infrared (fir) dust continuum in 27 quasars at redshifts 6.0 ≲ z < 6.7. we detect fir emission at ≳3σ in all quasar host galaxies with flux densities at ∼1900 ghz in the rest-frame of 0.12 < s rest,1900 ghz < 5.9 mjy, with a median (mean) flux density of 0.88 mjy (1.59 mjy). the implied fir luminosities range from {l}fir} = (0.27-13) × 1012 {l}⊙ , with 74% of our quasar hosts having {l}fir} > 1012 {l}⊙ . the estimated dust masses are {m}dust} = 107-109 {m}⊙ . if the dust is heated only by star formation, then the star formation rates in the quasar host galaxies are between 50 and 2700 {m}⊙{yr}}-1. in the framework of the host galaxy-black hole coevolution model a correlation between ongoing black hole growth and star formation in the quasar host galaxy would be expected. however, combined with results from the literature to create a luminosity-limited quasar sample, we do not find a strong correlation between quasar uv luminosity (a proxy for ongoing black hole growth) and fir luminosity (star formation in the host galaxy). the absence of such a correlation in our data does not necessarily rule out the coevolution model, and could be due to a variety of effects (including different timescales for black hole accretion and fir emission). | dust emission in an accretion-rate-limited sample of z ≳ 6 quasars |
observations of hyper-luminous quasars at z>6 reveal the rapid growth of supermassive black holes (smbhs ${\gt}10^9 \,\rm m_{\odot }$) whose origin is still difficult to explain. their progenitors may have formed as remnants of massive, metal-free stars (light seeds), via stellar collisions (medium-weight seeds) and/or massive gas clouds direct collapse (heavy seeds). in this work, we investigate for the first time the relative role of these three seed populations in the formation of z>6 smbhs within an eddington-limited gas accretion scenario. to this aim, we implement in our semi-analytical data-constrained model a statistical description of the spatial fluctuations of lyman-werner (lw) photodissociating radiation and of metal/dust enrichment. this allows us to set the physical conditions for black hole seeds formation, exploring their relative birth rate in a highly biased region of the universe at z>6. we find that the inclusion of medium-weight seeds does not qualitatively change the growth history of the first smbhs: although less massive seeds (${\lt}10^3\, \rm m_\odot$) form at a higher rate, the mass growth of a ${\sim}10^9\, \rm m_\odot$ smbh at z<15 is driven by efficient gas accretion (at a sub-eddington rate) on to its heavy progenitors ($10^5\, \rm m_\odot$). this conclusion holds independently of the critical level of lw radiation and even when medium-weight seeds are allowed to form in higher metallicity galaxies, via the so-called supercompetitive accretion scenario. our study suggests that the genealogy of z~6 smbhs is characterized by a rich variety of bh progenitors, which represent only a small fraction (${\lt} 10{-}20{{\ \rm per\ cent}}$) of all the bhs that seed galaxies at z>15. | light, medium-weight, or heavy? the nature of the first supermassive black hole seeds |
we present new near-infrared vlti/gravity interferometric spectra that spatially resolve the broad brγ emission line in the nucleus of the active galaxy iras 09149-6206. we use these data to measure the size of the broad line region (blr) and estimate the mass of the central black hole. using an improved phase calibration method that reduces the differential phase uncertainty to 0.05° per baseline across the spectrum, we detect a differential phase signal that reaches a maximum of ∼0.5° between the line and continuum. this represents an offset of ∼120 μas (0.14 pc) between the blr and the centroid of the hot dust distribution traced by the 2.3 μm continuum. the offset is well within the dust sublimation region, which matches the measured ∼0.6 mas (0.7 pc) diameter of the continuum. a clear velocity gradient, almost perpendicular to the offset, is traced by the reconstructed photocentres of the spectral channels of the brγ line. we infer the radius of the blr to be ∼65 μas (0.075 pc), which is consistent with the radius-luminosity relation of nearby active galactic nuclei derived based on the time lag of the hβ line from reverberation mapping campaigns. our dynamical modelling indicates the black hole mass is ∼1 × 108 m⊙, which is a little below, but consistent with, the standard mbh-σ* relation. | the spatially resolved broad line region of iras 09149-6206 |
we present a radio-quiet quasar at z = 0.237 discovered “turning on” by the intermediate palomar transient factory (iptf). the transient, iptf 16bco, was detected by iptf in the nucleus of a galaxy with an archival sloan digital sky survey spectrum with weak narrow-line emission characteristic of a low-ionization nuclear emission-line region (liner). our follow-up spectra show the dramatic appearance of broad balmer lines and a power-law continuum characteristic of a luminous ({l}{bol}≈ {10}45 erg s-1) type 1 quasar 12 yr later. our photometric monitoring with ptf from 2009-2012 and serendipitous x-ray observations from the xmm-newton slew survey in 2011 and 2015 constrain the change of state to have occurred less than 500 days before the iptf detection. an enhanced broad hα/[o iii] λ5007 line ratio in the type 1 state relative to other changing-look quasars also is suggestive of the most rapid change of state yet observed in a quasar. we argue that the >10 increase in eddington ratio inferred from the brightening in uv and x-ray continuum flux is more likely due to an intrinsic change in the accretion rate of a preexisting accretion disk than an external mechanism such as variable obscuration, microlensing, or the tidal disruption of a star. however, further monitoring will be helpful in better constraining the mechanism driving this change of state. the rapid “turn-on” of the quasar is much shorter than the viscous infall timescale of an accretion disk and requires a disk instability that can develop around a ∼ {10}8 {m}⊙black hole on timescales less than 1 yr. | iptf discovery of the rapid “turn-on” of a luminous quasar |
we report new observations of the cool diffuse gas around 29, $2.3<z<6.3$ galaxies, using deep jwst/nircam slitless grism spectroscopy around the sightline to the quasar j0100+2802. the galaxies span a stellar mass range of $7.1 \leq \log m_{*}/m_{sun} \leq 10.7$, and star-formation rates of $-0.1 < \log \; sfr/m_{sun}yr^{-1} \; <2.3$. we find galaxies for seven mgii absorption systems within 300 kpc of the quasar sightline. the mgii radial absorption profile falls off sharply with radii, with most of the absorption extending out to 2-3$r_{200}$ of the host galaxies. six out of seven mgii absorption systems are detected around galaxies with $\log m_{*}/m_{sun} >$9. mgii absorption kinematics are shifted from the systemic redshift of host galaxies with a median absolute velocity of 135 km/s and standard deviation of 85 km/s. the high kinematic offset and large radial separation ($r> 1.3 r_{200}$), suggest that five out of the seven mgii absorption systems are gravitationally not bound to the galaxies. in contrast, most cool circumgalactic media at $z<1$ are gravitationally bound. the high incidence of unbound mgii gas in this work suggests that towards the end of reionization, galaxy halos are in a state of remarkable disequilibrium, and are highly efficient in enriching the intergalactic medium. two strongest mgii absorption systems are detected at $z\sim$ 4.22 and 4.5, the former associated with a merging galaxy system and the latter associated with three kinematically close galaxies. both these galaxies reside in local galaxy over-densities, indicating the presence of cool mgii absorption in two "proto-groups" at $z>4$. | eiger iv: the cool 10$^4$k circumgalactic environment of high-$z$ galaxies reveals remarkably efficient igm enrichment |
cosmic reionization was the last major phase transition of hydrogen from neutral to highly ionized in the intergalactic medium (igm). current observations show that the igm is significantly neutral at z > 7 and largely ionized by z ~ 5.5. however, most methods to measure the igm neutral fraction are highly model dependent and are limited to when the volume-averaged neutral fraction of the igm is either relatively low ( ${\overline{x}}_{{\rm{h}}\,{\rm\small{i}}}\lesssim {10}^{-3}$ ) or close to unity ( ${\overline{x}}_{{\rm{h}}\,{\rm\small{i}}}\sim 1$ ). in particular, the neutral fraction evolution of the igm at the critical redshift range of z = 6-7 is poorly constrained. we present new constraints on ${\overline{x}}_{{\rm{h}}\,{\rm\small{i}}}$ at z ~ 5.1-6.8 by analyzing deep optical spectra of 53 quasars at 5.73 < z < 7.09. we derive model-independent upper limits on the neutral hydrogen fraction based on the fraction of "dark" pixels identified in the lyα and lyβ forests, without any assumptions on the igm model or the intrinsic shape of the quasar continuum. they are the first model-independent constraints on the igm neutral hydrogen fraction at z ~ 6.2-6.8 using quasar absorption measurements. our results give upper limits of ${\overline{x}}_{{\rm{h}}\,{\rm\small{i}}}(z=6.3)\lt 0.79\pm 0.04$ (1σ), ${\overline{x}}_{{\rm{h}}\,{\rm\small{i}}}(z=6.5)\lt 0.87\pm 0.03$ (1σ), and ${\overline{x}}_{{\rm{h}}\,{\rm\small{i}}}(z=6.7)\lt {0.94}_{-0.09}^{+0.06}$ (1σ). the dark pixel fractions at z > 6.1 are consistent with the redshift evolution of the neutral fraction of the igm derived from planck 2018. | (nearly) model-independent constraints on the neutral hydrogen fraction in the intergalactic medium at z 5-7 using dark pixel fractions in lyα and lyβ forests |
aims: the demographics of the production and escape of ionizing photons from uv-faint early galaxies is a key unknown that has hindered attempts to discover the primary drivers of reionization. with the advent of jwst, it is finally possible to observe the rest-frame optical nebular emission from individual sub-l*z > 3 galaxies to measure the production rate of ionizing photons, ξion.methods: here we study a sample of 370 z ∼ 3 − 7 galaxies spanning −23 < muv < −15.5 (median muv ≈ −18) with deep multiband hst and jwst/nircam photometry that covers the rest-uv to the optical from the glass and uncover jwst surveys. our sample includes 102 galaxies with lyman-alpha emission detected in muse spectroscopy. we used hα fluxes inferred from nircam photometry to estimate the production rate of ionizing photons that do not escape these galaxies, ξion(1 − fesc).results: we find median log10ξion(1 − fesc) = 25.33 ± 0.47, with a broad intrinsic scatter of 0.42 dex, which implies a broad range of galaxy properties and ages in our uv-faint sample. galaxies detected with lyman-alpha have ∼0.1 dex higher ξion(1 − fesc), which is explained by their higher hα equivalent width distribution; this implies younger ages and higher specific star formation rates and, thus, more o/b stars. we find significant trends of increasing ξion(1 − fesc) with increasing hα equivalent width, decreasing uv luminosity, and decreasing uv slope; this implies that the production of ionizing photons is enhanced in young galaxies with assumed low metallicities. we find no significant evidence for sources with very high ionizing escape fractions (fesc > 0.5) in our sample based on their photometric properties, even amongst the lyman-alpha-selected galaxies.conclusions: this work demonstrates that considering the full distribution of ξion across galaxy properties is important for assessing the primary drivers of reionization. catalogue is only available at the cds via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/j/a+a/672/a186 | the production of ionizing photons in uv-faint z ∼ 3-7 galaxies |
we present an independent examination of the parallax zero-point of the third gaia early data release (hereafter edr3), using the lamost primary red clump (prc) stellar sample. a median parallax offset of around 26 μas, slightly larger than that found by examination of distant quasars, is found for both the five- and six-parameter solutions in edr3, based on samples of over 63,000 and 2000 prc stars, respectively. similar to the previous investigation of lindegren et al., to which we compare our results, the parallax zero-point exhibits clear dependencies on the g magnitudes, colors, and positions of the objects. based on our analysis, the zero-point of the revised parallax can be reduced to a few μas, and some significant patterns, e.g., discontinuities with stellar magnitude, can be properly removed. however, relatively large offsets (>10 μas) are still found for the revised parallaxes over different positions on the sky. | the parallax zero-point of gaia early data release 3 from lamost primary red clump stars |
machine learning (ml) algorithms have revolutionized the way we interpret data in astronomy, particle physics, biology, and even economics, since they can remove biases due to a priori chosen models. here we apply a particular ml method, the genetic algorithms (ga), to cosmological data that describes the background expansion of the universe, namely the pantheon type ia supernovae and the hubble expansion history h (z ) datasets. we obtain model independent and nonparametric reconstructions of the luminosity distance dl(z ) and hubble parameter h (z ) without assuming any dark energy model or a flat universe. we then estimate the deceleration parameter q (z ), a measure of the acceleration of the universe, and we make a ∼4.5 σ model independent detection of the accelerated expansion, but we also place constraints on the transition redshift of the acceleration phase (ztr=0.662 ±0.027 ). we also find a deviation from λ cdm at high redshifts, albeit within the errors, hinting toward the recently alleged tension between the snia/quasar data and the cosmological constant λ cdm model at high redshifts (z ≳1.5 ). finally, we show the ga can be used in complementary null tests of the λ cdm via reconstructions of the hubble parameter and the luminosity distance. | what can machine learning tell us about the background expansion of the universe? |
this paper is the first in a series of preparing and analyzing spectral and other properties for a database of already discovered changing-look active galactic nuclei (cl agns). here, we focus on the spectral fitting and analysis of broad emission lines in an exhaustive sample of 112 cl agns available in the literature with existing sdss/boss/eboss spectroscopy. additionally, we have gathered older/newer spectral epochs from all the available sdss data releases to make the database more complete. we use pyqsofit and perform a homogeneous spectral decomposition of all of our sdss spectra and tabulate the agn continuum and emission-line properties per epoch per source, chronologically. this further allows us to categorize the sources in our sample as turn-on or turn-off and subsequently check for repeated occurrences of such phases. we then estimate the black hole mass (m$_{\rm bh}$) and the eddington ratio ($\lambda_{\rm edd}$) per epoch per source where the required parameters are available and well-estimated. we realize the movement of the source in the m$_{\rm bh}$-$\lambda_{\rm edd}$ plane allowing us to check for systematic changes in the source's fundamental properties. we then track their transition along the optical plane of the eigenvector 1 (ev1) schema and categorize sources that either stay within the same population (a or b) or make an inter-population movement as a function of spectral epoch. we also test the balmer decrement (h$\alpha$/h$\beta$) of a subset of our sample of cl agns as a function of time and agn luminosity. | changing-look agns -- i. tracking the transition on the main sequence of quasars |
we introduce arepo-rt, a novel radiation hydrodynamic (rhd) solver for the unstructured moving-mesh code arepo. our method solves the moment-based radiative transfer equations using the m1 closure relation. we achieve second-order convergence by using a slope-limited linear spatial extrapolation and a first-order time prediction step to obtain the values of the primitive variables on both sides of the cell interface. a harten-lax-van leer flux function, suitably modified for moving meshes, is then used to solve the riemann problem at the interface. the implementation is fully conservative and compatible with the individual time-stepping scheme of arepo. it incorporates atomic hydrogen (h) and helium (he) thermochemistry, which is used to couple the ultraviolet radiation field to the gas. additionally, infrared (ir) radiation is coupled to the gas under the assumption of local thermodynamic equilibrium between the gas and the dust. we successfully apply our code to a large number of test problems, including applications such as the expansion of h ii regions, radiation pressure-driven outflows, and the levitation of optically thick layer of gas by trapped ir radiation. the new implementation is suitable for studying various important astrophysical phenomena, such as the effect of radiative feedback in driving galactic scale outflows, radiation-driven dusty winds in high-redshift quasars, or simulating the reionization history of the universe in a self-consistent manner. | arepo-rt: radiation hydrodynamics on a moving mesh |
because most large galaxies contain a central black hole, and galaxies often merge, black-hole binaries are expected to be common in galactic nuclei. although they cannot be imaged, periodicities in the light curves of quasars have been interpreted as evidence for binaries, most recently in pg 1302-102, which has a short rest-frame optical period of four years (ref. 6). if the orbital period of the black-hole binary matches this value, then for the range of estimated black-hole masses, the components would be separated by 0.007-0.017 parsecs, implying relativistic orbital speeds. there has been much debate over whether black-hole orbits could be smaller than one parsec (ref. 7). here we report that the amplitude and the sinusoid-like shape of the variability of the light curve of pg 1302-102 can be fitted by relativistic doppler boosting of emission from a compact, steadily accreting, unequal-mass binary. we predict that brightness variations in the ultraviolet light curve track those in the optical, but with a two to three times larger amplitude. this prediction is relatively insensitive to the details of the emission process, and is consistent with archival ultraviolet data. follow-up ultraviolet and optical observations in the next few years can further test this prediction and confirm the existence of a binary black hole in the relativistic regime. | relativistic boost as the cause of periodicity in a massive black-hole binary candidate |
we use atacama large millimeter array observations of the host galaxy of the quasar ulas j1342+0928 at z = 7.54, to study the dust continuum and far-infrared lines emitted from its interstellar medium (ism). the rayleigh-jeans tail of the dust continuum is well sampled with eight different spectral setups, and from a modified blackbody fit we obtain an emissivity coefficient of β = 1.85 ± 0.3. assuming a standard dust temperature of 47 k we derive a dust mass of m dust = 0.35 × 108 m ⊙ and a star formation rate of 150+/- 30 {m}⊙{yr}}-1. we have >4σ detections of the {[{{c}}{{ii}}]}158μ {{m}}, {[{{o}}{{iii}}]}88μ {{m}}, and {[{{n}}{{ii}}]}205μ {{m}} atomic fine structure lines and limits on the {[{{c}}{{i}}]}369μ {{m}}, {[{{o}}{{i}}]}146μ {{m}}, and {[{{n}}{{ii}}]}205μ {{m}} emission. we also report multiple limits of co rotational lines with j up ≥ 7, as well as a tentative 3.3σ detection of the stack of four co lines (j up = 11, 10, 8, and 7). we find line deficits that are in agreement with local ultra-luminous infrared galaxies. comparison of the {[{{n}}{{ii}}]}205μ {{m}} and {[{{c}}{{ii}}]}158μ {{m}} lines indicates that the {[{{c}}{{ii}}]}158μ {{m}} emission arises predominantly from the neutral medium, and we estimate that the photodisassociation regions in j1342+0928 have densities ≲5 × 104 cm-3. the data suggest that ∼16% of hydrogen is in ionized form and that the h ii regions have high electron densities of ne> 180 cm-3. our observations favor a low gas-to-dust ratio of <100, and a metallicity of the ism comparable to the solar value. all the measurements presented here suggest that the host galaxy of j1342+0928 is highly enriched in metal and dust, despite being observed just 680 myr after the big bang. | an alma multiline survey of the interstellar medium of the redshift 7.5 quasar host galaxy j1342+0928 |
context. ultra-compact structure in radio sources (especially in quasars that can be observed up to very high redshifts), with milliarcsecond angular sizes measured by very-long-baseline interferometry (vlbi), is becoming an important astrophysical tool for probing both cosmology and the physical properties of agn.aims: we present a newly compiled data set of 120 milliarcsec. compact radio sources representing intermediate-luminosity quasars covering the redshift range 0.46 < z < 2.76 and check the possibility of using these sources as independent cosmological probes. these quasars observed at 2.29 ghz show negligible dependence on redshifts and intrinsic luminosity, and thus represent a fixed comoving-length of standard ruler.methods: for a cosmological ruler with intrinsic length lm, the angular size-redshift relation can be written as θ(z) = lm/da(z, where θ(z) is the angular size at redshift z, and da(z) is the corresponding angular diameter distance. we use a compilation of angular size and redshift data for ultra-compact radio sources from a well-known vlbi survey, and implement a new cosmology-independent technique to calibrate the linear size of this standard ruler, which is also used to test different cosmological models with and without the flat universe assumption.results: we determine the linear size of this standard ruler as lm = 11.03 ± 0.25 pc, which is the typical radius at which agn jets become opaque at the observed frequency ν 2 ghz. our measurement of this linear size is also consistent with the previous and recent radio observations at other different frequencies. in the framework of flat λcdm model, we find a high value of the matter density parameter, ωm = 0.322+0.244-0.141, and a low value of the hubble constant, h0 = 67.6+7.8-7.4 km s-1 mpc-1, which is in excellent agreement with the cosmic microwave background (cmb) anisotropy measurements by planck. we obtain ωm = 0.309+0.215-0.151, w = -0.970+0.500-1.730 at 68.3% cl for the constant w of a dynamical dark-energy model, which demonstrates no significant deviation from the concordance λcdm model. consistent fitting results are also obtained for other cosmological models explaining the cosmic acceleration, like ricci dark energy (rde) or the dvali-gabadadze-porrati (dgp) brane-world scenario. while no significant change in w with redshift is detected, there is still considerable room for evolution in w and the transition redshift at which w departing from -1 is located at z 2.0. our results demonstrate that the method extensively investigated in our work on observational radio quasar data can be used to effectively derive cosmological information. finally, we find the combination of high-redshift quasars and low-redshift clusters may provide an important source of angular diameter distances, considering the redshift coverage of these two astrophysical probes. | ultra-compact structure in intermediate-luminosity radio quasars: building a sample of standard cosmological rulers and improving the dark energy constraints up to z 3 |
ss433 is the only galactic binary system known to persistently accrete at highly super-critical (or hyper-critical) rates, similar to those in tidal disruption events, and likely needed to explain the rapid growth of those very high redshift quasars containing massive smbhs. probing the inner regions of ss433 in the x-rays is crucial to understanding this system, and super-critical accretion in general, but is highly challenging due to obscuration by the surrounding wind, driven from the accretion flow. nustar observed ss433 in the hard x-ray band across multiple phases of its 162 d superorbital precession period. spectral-timing tools allow us to infer that the hard x-ray emission from the inner regions is likely being scattered towards us by the walls of the wind-cone. by comparing to numerical models, we determine an intrinsic x-ray luminosity of ≥ 2 × 1037 erg s-1 and that, if viewed face on, we would infer an apparent luminosity of >1 × 1039 erg s-1, confirming ss433's long-suspected nature as an ultraluminous x-ray source (ulx). we present the discovery of a narrow, ~100 s lag due to atomic processes occurring in outflowing material travelling at least 0.14-0.29c, which matches absorption lines seen in ulxs and - in the future - will allow us to map a super-critical outflow for the first time. | nustar reveals the hidden nature of ss433 |
we interpret recent alma observations of z > 6 normal star-forming galaxies by means of a seminumerical method, which couples the output of a cosmological hydrodynamical simulation with a chemical evolution model which accounts for the contribution to dust enrichment from supernovae, asymptotic giant branch stars and grain growth in the interstellar medium. we find that while stellar sources dominate the dust mass of small galaxies, the higher level of metal enrichment experienced by galaxies with mstar > 109 m⊙ allows efficient grain growth, which provides the dominant contribution to the dust mass. even assuming maximally efficient supernova dust production, the observed dust mass of the z = 7.5 galaxy a1689-zd1 requires very efficient grain growth. this, in turn, implies that in this galaxy the average density of the cold and dense gas, where grain growth occurs, is comparable to that inferred from observations of quasar (qso) host galaxies at similar redshifts. although plausible, the upper limits on the dust continuum emission of galaxies at 6.5 < z < 7.5 show that these conditions must not apply to the bulk of the high-redshift galaxy population. | the dust mass in z > 6 normal star-forming galaxies. |
we measure the host galaxy properties of five quasars with z ~ 1.6-3.5 selected from the sloan digital sky survey (sdss) and aegis, which fall within the jwst/hubble space telescope (hst) ceers survey area. a point-spread function library is constructed based on stars in the full field of view of the data and used with the 2d image modeling tool galight to decompose the quasar and its host with multiband filters available for hst acs+wfc3 and jwst nircam (12 filters covering hst f606w to jwst f444w). as demonstrated, jwst provides the first capability to detect quasar hosts at z > 3 and enables spatially resolved studies of the underlying stellar populations at z ~ 2 within morphological structures (spiral arms, bar) not possible with hst. overall, we find quasar hosts to be disk-like, lack merger signatures, and have sizes generally more compact than typical star-forming galaxies at their respective stellar mass, thus in agreement with results at lower redshifts. the fortuitous face-on orientation of sdssj1420+5300a at z = 1.646 enables us to find higher star formation and younger ages in the central 2-4 kpc region relative to the outskirts, which may help explain the relatively compact nature of quasar hosts and pose a challenge to active galactic nucleus feedback models. | opening the era of quasar-host studies at high redshift with jwst |
we present x-shooter at very large telescope observations of a sample of 10 luminous, x-ray obscured quasi-stellar objects (qsos) at z ∼ 1.5 from the xmm-cosmos survey, expected to be caught in the transitioning phase from starburst to active galactic nucleus (agn)-dominated systems. the main selection criterion is x-ray detection at bright fluxes (lx ≳ 1044 erg s-1) coupled to red optical-to-near-infrared-to-mid-infrared colours. thanks to its large wavelength coverage, x-shooter allowed us to determine accurate redshifts from the presence of multiple emission lines for five out of six targets for which we had only a photometric redshift estimate, with an 80 per cent success rate, significantly larger than what is observed in similar programs of spectroscopic follow-up of red qsos. we report the detection of broad and shifted components in the [o iii] λλ5007, 4959 complexes for six out of eight sources with these lines observable in regions free from strong atmospheric absorptions. the full width at half-maximum (fwhm) associated with the broad components are in the range fwhm ∼ 900-1600 km s-1, larger than the average value observed in sloan digital sky survey type 2 agn samples at similar observed [o iii] luminosity, but comparable to those observed for qso/ultraluminous infrared galaxies systems for which the presence of kpc scale outflows has been revealed through integral field unit spectroscopy. although the total outflow energetics (inferred under reasonable assumptions) may be consistent with winds accelerated by stellar processes, we favour an agn origin for the outflows given the high outflow velocities observed (v > 1000 km s-1) and the presence of strong winds also in objects undetected in the far-infrared. | x-shooter reveals powerful outflows in z ∼ 1.5 x-ray selected obscured quasi-stellar objects |
models that address both the hubble and s8 tensions with the same mechanism generically cause a prerecombination suppression of the small scale matter power spectrum. here we focus on two such models. both models introduce a self-interacting dark radiation fluid scattering with dark matter, which has a step in its abundance around some transition redshift. in one model, the interaction is weak and with all of the dark matter whereas in the other it is strong but with only a fraction of the dark matter. the weakly interacting case is able to address both tensions simultaneously and provide a good fit to a the planck measurements of the cosmic microwave background (cmb), the pantheon type ia supernovae, and a combination of low and high redshift baryon acoustic oscillation data, whereas the strongly interacting model cannot significantly ease both tensions simultaneously. the addition of high-resolution cmb measurements (act dr4 and spt-3g) slightly limits both model's ability to address the hubble tension. the use of the effective field theory of large-scale structures analysis of boss dr12 lrg and eboss dr16 qso data additionally limits their ability to address the s8 tension. we explore how these models respond to these datasets in detail in order to draw general conclusions about what is required for a mechanism to address both tensions. we find that in order to fit the cmb data the time dependence of the suppression of the matter power spectrum plays a central role. | comparative analysis of interacting stepped dark radiation |
identifying and characterizing reionized bubbles enables us to track both their size distribution, which depends on the primary ionizing sources, and the relationship between reionization and galaxy evolution. we demonstrate that spectrally resolved z ≳ 6 lyman-alpha (lyα) emission can constrain properties of reionized regions. specifically, the distance from a source to a neutral region sets the minimum observable lyα velocity offset from systemic. detection of flux on the blue side of the lyα resonance implies the source resides in a large, sufficiently ionized region that photons can escape without significant resonant absorption, and thus constrains both the sizes of and the residual neutral fractions within ionized bubbles. we estimate the extent of the region around galaxies which is optically thin to blue lyα photons, analogous to quasar proximity zones, as a function of the source's ionizing photon output and surrounding gas density. this optically thin region is typically ≲ 0.3 pmpc in radius (allowing transmission of flux ≳ -250 km s-1), ≲ 20 per cent of the distance to the neutral region. in a proof-of-concept, we demonstrate the z ≈ 6.6 galaxy cola1 - with a blue lyα peak - likely resides in an ionized region >0.7 pmpc, with residual neutral fraction <10-5.5. to ionize its own proximity zone we infer cola1 has a high ionizing photon escape fraction (fesc > 0.50), relatively steep uv slope (β < -1.79), and low line-of-sight gas density (~0.5 times the cosmic mean), suggesting it is a rare, underdense line-of-sight. | measuring the properties of reionized bubbles with resolved lyα spectra |
we present and validate the catalog of lyman-α forest fluctuations for 3d analyses using the early data release (edr) from the dark energy spectroscopic instrument (desi) survey. we used 88,511 quasars collected from desi survey validation (sv) data and the first two months of the main survey (m2). we present several improvements to the method used to extract the lyman-α absorption fluctuations performed in previous analyses from the sloan digital sky survey (sdss). in particular, we modify the weighting scheme and show that it can improve the precision of the correlation function measurement by more than 20%. this catalog can be downloaded from https://data.desi.lbl.gov/public/edr/vac/edr/lya/fuji/v0.3, and it will be used in the near future for the first desi measurements of the 3d correlations in the lyman-α forest. | the lyman-α forest catalog from the dark energy spectroscopic instrument early data release |
the forest of lyman-α absorption lines detected in the spectra of distant quasars encodes information on the nature and properties of dark matter and the thermodynamics of diffuse baryonic material. its main observable—the 1d flux power spectrum (fps)—should exhibit a suppression on small scales and an enhancement on large scales in warm dark matter (wdm) cosmologies compared to standard λ cdm . here, we present an unprecedented suite of 1080 high-resolution cosmological hydrodynamical simulations run with the graphics processing unit-accelerated code cholla to study the evolution of the lyman-α forest under a wide range of physically motivated gas thermal histories along with different free-streaming lengths of wdm thermal relics in the early universe. a statistical comparison of synthetic data with the forest fps measured down to the smallest velocity scales ever probed at redshifts 4.0 ≲z ≲5.2 [e. boera et al., revealing reionization with the thermal history of the intergalactic medium: new constraints from the ly α flux power spectrum, astrophys. j. 872, 101 (2019), 10.3847/1538-4357/aafee4] yields a lower-limit mwdm>3.1 kev (95% c.l.) for the wdm particle mass and constrains the amplitude and spectrum of the photoheating and photoionizing background produced by star-forming galaxies and active galactic nuclei at these redshifts. interestingly, our bayesian inference analysis appears to weakly favor wdm models with a peak likelihood value at the thermal relic mass of mwdm=4.5 kev . we find that the suppression of the fps from free-streaming saturates at k ≳0.1 s km−1 because of peculiar velocity smearing, and this saturated suppression combined with a slightly lower gas temperature provides a moderately better fit to the observed small-scale fps for wdm cosmologies. | new constraints on warm dark matter from the lyman-α forest power spectrum |
we present the first results from the kmos (k-band multi-object spectrograph) agn (active galactic nuclei) survey at high redshift (kashz), a vlt/kmos integral-field spectroscopic (ifs) survey of z ≳ 0.6 agn. we present galaxy-integrated spectra of 89 x-ray agn (l2-10 kev = 1042-1045 erg s-1), for which we observed [o iii] (z ≈ 1.1-1.7) or hα emission (z ≈ 0.6-1.1). the targets have x-ray luminosities representative of the parent agn population and we explore the emission-line luminosities as a function of x-ray luminosity. for the [o iii] targets, ≈50 per cent have ionized gas velocities indicative of gas that is dominated by outflows and/or highly turbulent material (i.e. overall line widths ≳600 km s-1). the most luminous half (i.e. lx > 6 × 1043 erg s-1) have a ≳2 times higher incidence of such velocities. on the basis of our results, we find no evidence that x-ray obscured agn are more likely to host extreme kinematics than unobscured agn. our kashz sample has a distribution of gas velocities that is consistent with a luminosity-matched sample of z < 0.4 agn. this implies little evolution in the prevalence of ionized outflows, for a fixed agn luminosity, despite an order-of-magnitude decrease in average star formation rates over this redshift range. furthermore, we compare our hα targets to a redshift-matched sample of star-forming galaxies and despite a similar distribution of hα luminosities and likely star formation rates, we find extreme ionized gas velocities are up to ≈10 times more prevalent in the agn-host galaxies. our results reveal a high prevalence of extreme ionized gas velocities in high-luminosity x-ray agn and imply that the most powerful ionized outflows in high-redshift galaxies are driven by agn activity. | the kmos agn survey at high redshift (kashz): the prevalence and drivers of ionized outflows in the host galaxies of x-ray agn |
we employ cosmological hydrodynamical simulations to investigate the effects of agn feedback on the formation of massive galaxies with present-day stellar masses of m_stel= 8.8 × 10^{10}-6.0 × 10^{11} m_{⊙}. using smoothed particle hydrodynamics simulations with a pressure-entropy formulation that allows an improved treatment of contact discontinuities and fluid mixing, we run three sets of simulations of 20 haloes with different agn feedback models: (1) no feedback, (2) thermal feedback, and (3) mechanical and radiation feedback. we assume that seed black holes are present at early cosmic epochs at the centre of emerging dark matter haloes and trace their mass growth via gas accretion and mergers with other black holes. both feedback models successfully recover the observed mbh-σ relation and black hole-to-stellar mass ratio for simulated central early-type galaxies. the baryonic conversion efficiencies are reduced by a factor of 2 compared to models without any agn feedback at all halo masses. however, massive galaxies simulated with thermal agn feedback show a factor of ∼10-100 higher x-ray luminosities than observed. the mechanical/radiation feedback model reproduces the observed correlation between x-ray luminosities and velocity dispersion, e.g. for galaxies with σ = 200 km s- 1, the x-ray luminosity is reduced from 1042 erg s- 1 to 1040 erg s- 1. it also efficiently suppresses late-time star formation, reducing the specific star formation rate from 10-10.5 yr- 1 to 10-14 yr- 1 on average and resulting in quiescent galaxies since z = 2, whereas the thermal feedback model shows higher late-time in situ star formation rates than observed. | the impact of mechanical agn feedback on the formation of massive early-type galaxies |
we use 78 reverberation-measured mg ii time-lag quasars (qsos) in the redshift range 0.0033 ≤ z ≤ 1.89 to constrain cosmological parameters in six different cosmological models. the basis of our method is the use of the radius-luminosity or r-l relation to standardize these 78 mg ii qsos. in each cosmological model, we simultaneously determine r-l relation and cosmological model parameters, thus avoiding the circularity problem. we find that the r-l relation parameter values are independent of the cosmological model used in the analysis, thus, establishing that current mg ii qsos are standardizable candles. cosmological constraints obtained using these qsos are significantly weaker than, but consistent with, those obtained from a joint analysis of baryon acoustic oscillation (bao) observations and hubble parameter [h(z)] measurements. so, we also analyse these qsos in conjunction with the bao + h(z) data and find cosmological constraints consistent with the standard spatially flat λcdm model as well as with mild dark energy dynamics and a little spatial curvature. a larger sample of higher quality reverberation-measured qsos should have a smaller intrinsic dispersion and so should provide tighter constraints on cosmological parameters. | standardizing reverberation-measured mg ii time-lag quasars, by using the radius-luminosity relation, and constraining cosmological model parameters |
we present a study of metal-enriched halo gas traced by mg ii and c iv absorption at z < 2 in the muse analysis of gas around galaxies survey and the quasar sightline and galaxy evolution survey. using these large and complete galaxy surveys in quasar fields, we study the dependence of the metal distribution on galaxy properties and overdensities, out to physical projected separations of 750 kpc. we find that the cool, low-ionization gas is significantly affected by the environment across the full redshift range probed, with ≈2-3 times more prevalent and stronger mg ii absorption in higher overdensity group environments and in regions with greater overall stellar mass and star formation rates. complementary to these results, we have further investigated the more highly ionized gas as traced by c iv absorption, and found that it is likely to be more extended than the mg ii gas, with ≈2 times higher covering fraction at a given distance. we find that the strength and covering fraction of c iv absorption show less significant dependence on galaxy properties and environment than the mg ii absorption, but more massive and star-forming galaxies nevertheless also show ≈2 times higher incidence of c iv absorption. the incidence of mg ii and c iv absorption within the virial radius shows a tentative increase with redshift, being higher by a factor of ≈1.5 and ≈4, respectively, at z > 1. it is clear from our results that environmental processes have a significant impact on the distribution of metals around galaxies and need to be fully accounted for when analysing correlations between gaseous haloes and galaxy properties. | metal-enriched halo gas across galaxy overdensities over the last 10 billion years |
we present reverberation mapping (rm) results for 17 high-redshift, high-luminosity quasars with good-quality r-band and emission-line light curves. we are able to measure statistically significant lags for lyα (11 objects), si iv (5 objects), c iv (11 objects), and c iii] (2 objects). using our results and previous lag determinations taken from the literature, we present an updated c iv radius-luminosity relation and provide for the first time radius-luminosity relations for lyα, si iv, and c iii]. while in all cases the slopes of the correlations are statistically significant, the zero points are poorly constrained because of the lack of data at the low-luminosity end. we find that the emissivity-weighted distances from the central source of the lyα, si iv, and c iii] line-emitting regions are all similar, which corresponds to about half that of the hβ region. we also find that 3/17 of our sources show an unexpected behavior in some emission lines, two in the lyα light curve and one in the si iv light curve, in that they do not seem to follow the variability of the uv continuum. finally, we compute rm black hole (bh) masses for those quasars with highly significant lag measurements and compare them with c iv single-epoch (se) mass determinations. we find that the rm-based bh mass determinations seem smaller than those found using se calibrations. | reverberation mapping of luminous quasars at high z |
we use 317,000 emission-line galaxies from the sloan digital sky survey to investigate line-ratio selection of active galactic nuclei (agns). in particular, we demonstrate that “star formation (sf) dilution” by h ii regions causes a significant bias against agn selection in low-mass, blue, star-forming, disk-dominated galaxies. this bias is responsible for the observed preference of agns among high-mass, green, moderately star-forming, bulge-dominated hosts. we account for the bias and simulate the intrinsic population of emission-line agns using a physically motivated eddington ratio distribution, intrinsic agn narrow line region line ratios, a luminosity-dependent {l}{bol}/l[{{o}} {{iii}}] bolometric correction, and the observed {m}{bh}-σ relation. these simulations indicate that, in massive ({log}({m}*/{m}⊙ )≳ 10) galaxies, agn accretion is correlated with specific star formation rate (sfr) but is otherwise uniform with stellar mass. there is some hint of lower black hole occupation in low-mass ({log}({m}*/{m}⊙ )≲ 10) hosts, although our modeling is limited by uncertainties in measuring and interpreting the velocity dispersions of low-mass galaxies. the presence of sf dilution means that agns contribute little to the observed strong optical emission lines (e.g., [{{o}} {{iii}}] and {{h}}α ) in low-mass and star-forming hosts. however the agn population recovered by our modeling indicates that feedback by typical (low- to moderate-accretion) low-redshift agns has nearly uniform efficiency at all stellar masses, sfrs, and morphologies. taken together, our characterization of the observational bias and resultant agn occupation function suggest that agns are unlikely to be the dominant source of sf quenching in galaxies, but instead are fueled by the same gas which drives sf activity. | the biases of optical line-ratio selection for active galactic nuclei and the intrinsic relationship between black hole accretion and galaxy star formation |
we present an x-ray and multiwavelength study of 33 weak emission-line quasars (wlqs) and 18 quasars that are analogs of the extreme wlq, phl 1811, at z≈ 0.5-2.9. new chandra 1.5-9.5 ks exploratory observations were obtained for 32 objects while the others have archival x-ray observations. significant fractions of these luminous type 1 quasars are distinctly x-ray weak compared to typical quasars, including 16 (48%) of the wlqs and 17 (94%) of the phl 1811 analogs with average x-ray weakness factors of 17 and 39, respectively. we measure a relatively hard ({γ }=1.16-0.32+0.37) effective power-law photon index for a stack of the x-ray weak subsample, suggesting x-ray absorption, and spectral analysis of one phl 1811 analog, j1521+5202, also indicates significant intrinsic x-ray absorption. we compare composite sloan digital sky survey spectra for the x-ray weak and x-ray normal populations and find several optical-uv tracers of x-ray weakness, e.g., fe ii rest-frame equivalent width (rew) and relative color. we describe how orientation effects under our previously proposed “shielding-gas” scenario can likely unify the x-ray weak and x-ray normal populations. we suggest that the shielding gas may naturally be understood as a geometrically thick inner accretion disk that shields the broad line region from the ionizing continuum. if wlqs and phl 1811 analogs have very high eddington ratios, the inner disk could be significantly puffed up (e.g., a slim disk). shielding of the broad emission-line region by a geometrically thick disk may have a significant role in setting the broad distributions of c iv rew and blueshift for quasars more generally. | x-ray insights into the nature of phl 1811 analogs and weak emission-line quasars: unification with a geometrically thick accretion disk? |
the global influence of agn-driven outflows remains uncertain, due to a lack of large samples with accurately determined outflow properties. in the second paper of this series, we determine the mass and energetics of ionized outflows in 234 type ii agn, the largest such sample to date, by combining the infrared emission of the dust in the wind (paper i) with the emission-line properties. we provide new general expressions for the properties of the outflowing gas, which depend on the ionization state of the gas. we also present a novel method to estimate the electron density in the outflow, based on optical line ratios and on the known location of the wind. the inferred electron densities, ne ∼ 10^{4.5} cm^{-3}, are two orders of magnitude larger than typically assumed in most other cases of ionized outflows. we argue that the discrepancy is due to the fact that the commonly-used [s ii]-based method underestimates the true density by a large factor. as a result, the inferred mass outflow rates and kinetic coupling efficiencies are \dot{m}_{out} ∼ 10^{-2} (m_{\odot yr^{-1})} and ɛ = \dot{e}_{kin}/l_{bol} ∼ 10^{-5} , respectively, one to two orders of magnitude lower than previous estimates. our analysis suggests the existence of a significant amount of neutral atomic gas at the back of the outflowing ionized gas clouds, with mass that is a factor of a few larger than the observed ionized gas mass. this has significant implications for the estimated mass and energetics of such flows. | discovering agn-driven winds through their infrared emission - ii. mass outflow rate and energetics |
we study how runaway stellar collisions in high-redshift, metal-poor star clusters form very massive stars (vmss) that can directly collapse to intermediate-mass black holes (imbhs). we follow the evolution of a pair of neighbouring high-redshift mini-haloes with high-resolution, cosmological hydrodynamical zoom-in simulations using the adaptive mesh refinement code ramses combined with the non-equilibrium chemistry package krome. the first collapsing mini-halo is assumed to enrich the central nuclear star cluster (nsc) of the other to a critical metallicity, sufficient for population ii (pop. ii) star formation at redshift z ≈ 27. using the spatial configuration of the flattened, asymmetrical gas cloud forming in the core of the metal-enriched halo, we set the initial conditions for simulations of an initially non-spherical star cluster with the direct summation code nbody6 which are compared to about 2000 nbody6 simulations of spherical star clusters for a wide range of star cluster parameters. the final mass of the vms that forms depends strongly on the initial mass and initial central density of the nsc. for the initial central densities suggested by our ramses simulations, vmss with mass >400 m⊙ can form in clusters with stellar masses of ≈104 m⊙, and this can increase to well over 1000 m⊙ for more massive and denser clusters. the high probability we find for forming a vms in these mini-haloes at such an early cosmic time makes collisional runaway of pop. ii star clusters a promising channel for producing large numbers of high-redshift imbhs that may act as the seeds of supermassive black holes. | seeding high-redshift qsos by collisional runaway in primordial star clusters |
we have initiated a new survey for local extremely metal-poor galaxies (empgs) with subaru/hyper suprime-cam (hsc) large-area (∼500 deg2) optical images reaching a 5σ limit of ∼26 mag, about 100 times deeper than the sloan digital sky survey (sdss). to select z/z⊙ < 0.1 empgs from ∼40 million sources detected in the subaru images, we first develop a machine-learning (ml) classifier based on a deep neural network algorithm with a training data set consisting of optical photometry of galaxy, star, and qso models. we test our ml classifier with sdss objects having spectroscopic metallicity measurements and confirm that our ml classifier accomplishes 86% completeness and 46% purity empg classifications with photometric data. applying our ml classifier to the photometric data of the subaru sources, as well as faint sdss objects with no spectroscopic data, we obtain 27 and 86 empg candidates from the subaru and sdss photometric data, respectively. we conduct optical follow-up spectroscopy for 10 of our empg candidates with magellan/ldss-3+mage, keck/deimos, and subaru/focas and find that the 10 empg candidates are star-forming galaxies at z = 0.007-0.03 with large hβ equivalent widths of 104-265 å, stellar masses of log( ${m}_{\star }$ / ${m}_{\odot }$ ) = 5.0-7.1, and high specific star formation rates of ∼300 gyr-1, which are similar to those of early galaxies at z ≳ 6 reported recently. we spectroscopically confirm that 3 out of 10 candidates are truly empgs with z/z⊙ < 0.1, one of which is hsc j1631+4426, the most metal-poor galaxy, with z/z⊙ = 0.016, ever reported. * partly based on data obtained with the subaru telescope. the subaru telescope is operated by the national astronomical observatory of japan. † the data presented herein were partly 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. ‡ this paper includes data gathered with the 6.5 m magellan telescopes located at las campanas observatory, chile. | extremely metal-poor representatives explored by the subaru survey (empress). i. a successful machine-learning selection of metal-poor galaxies and the discovery of a galaxy with m* < 106 m⊙ and 0.016 z⊙ |
we present an in-depth and systematic variability study of a sample of 20 powerful blazars, including 12 bl lacs and 8 flat-spectrum radio quasars, applying various analysis tools such as flux distribution, symmetry analysis, and time-series analysis on the decade-long fermi/lat observations. the results show that blazars with steeper γ-ray spectral indexes are found to be more variable, and the γ-ray flux distribution closely resembles a log-normal probability distribution function. the statistical variability properties of the sources as studied by power spectral density analysis are consistent with flicker noise (p(ν) ∝ 1/ν)—an indication of long-memory processes at work. statistical analysis of the distribution of flux rise and decay rates in the light curves of the sources, aimed at distinguishing between particle acceleration and energy-dissipation timescales, counterintuitively suggests that both kinds of rates follow a similar distribution and the derived mean variability timescales are on the order of a few weeks. the corresponding emission region size is used to constrain the location of γ-ray production sites in the sources to be a few parsecs. additionally, using lomb-scargle periodogram and weighted wavelet z-transform methods and extensive monte carlo simulations, we detected year-timescale quasi-periodic oscillations in the sources s5 0716+714, mrk 421, on +325, pks 1424-418, and pks 2155-304. the detection significance was computed taking proper account of the red noise and other artifacts inherent in the observations. we explain the results in light of current blazar models with relativistic shocks propagating down the jet viewed close to the line of sight. | the nature of γ-ray variability in blazars |
project amiga (absorption maps in the gas of andromeda) is a survey of the circumgalactic medium (cgm) of andromeda (m31, ${r}_{\mathrm{vir}}$ ≃ 300 kpc) along 43 qso sightlines at impact parameters 25 ≤ r ≤ 569 kpc (25 at r ≲ ${r}_{\mathrm{vir}}$). we use ultraviolet absorption measurements of si ii, si iii, si iv, c ii, and c iv from the hubble space telescope/cosmic origins spectrograph and o iv from the far ultraviolet spectroscopic explorer to provide an unparalleled look at how the physical conditions and metals are distributed in the cgm of m31. we find that si iii and o vi have a covering factor near unity for r ≲ 1.2 ${r}_{\mathrm{vir}}$ and ≲1.9 ${r}_{\mathrm{vir}}$, respectively, demonstrating that m31 has a very extended ∼104-105.5 k ionized cgm. the metal and baryon masses of the 104-105.5 k cgm gas within ${r}_{\mathrm{vir}}$ are ≳108 and ≳4 × 1010 (z/0.3 z⊙)-1 m⊙, respectively. there is not much azimuthal variation in the column densities or kinematics, but there is with r. the cgm gas at r ≲ 0.5 ${r}_{\mathrm{vir}}$ is more dynamic and has more complicated, multiphase structures than at larger radii, perhaps a result of more direct impact of galactic feedback in the inner regions of the cgm. several absorbers are projected spatially and kinematically close to m31 dwarf satellites, but we show that those are unlikely to give rise to the observed absorption. cosmological zoom simulations of ∼l* galaxies have o vi extending well beyond ${r}_{\mathrm{vir}}$ as observed for m31 but do not reproduce well the radial column density profiles of the lower ions. however, some similar trends are also observed, such as the lower ions showing a larger dispersion in column density and stronger dependence on r than higher ions. based on our findings, it is likely that the milky way has a ∼104-105.5 k cgm as extended as for m31 and their cgm (especially the warm-hot gas probed by o vi) are overlapping. * based on observations made with the nasa/esa hubble space telescope, obtained from the data archive at the space telescope science institute. stsci is operated by the association of universities for research in astronomy, inc., under nasa contract nas 5-26555. | project amiga: the circumgalactic medium of andromeda |
the last 25 years saw a major step forward in the analysis of optical and uv spectroscopic data of large quasar samples. multivariate statistical approaches have led to the definition of systematic trends in observational properties that are the basis of physical and dynamical modeling of quasar structure. we discuss the empirical correlates of the so-called “main sequence” associated with the quasar eigenvector 1, its governing physical parameters and several implications on our view of the quasar structure, as well as some luminosity effects associated with the virialized component of the line emitting regions. we also briefly discuss quasars in a segment of the main sequence that includes the strongest feii emitters. these sources show a small dispersion around a well-defined eddington ratio value, a property which makes them potential eddington standard candles. | a main sequence for quasars |
this review describes the events leading up to the discovery of the kerr metric in 1963 and the enormous impact the discovery has had in the subsequent 50 years. the review discusses the penrose process, the four laws of black hole mechanics, uniqueness of the solution, and the no-hair theorems. it also includes kerr perturbation theory and its application to black hole stability and quasi-normal modes. the kerr metric's importance in the astrophysics of quasars and accreting stellar-mass black hole systems is detailed. a theme of the review is the 'miraculous' nature of the solution, both in describing in a simple analytic formula the most general rotating black hole, and in having unexpected mathematical properties that make many calculations tractable. also included is a pedagogical derivation of the solution suitable for a first course in general relativity. | the kerr metric |
quasi-stellar object (qso) spectral templates are important both to qso physics and for investigations that use qsos as probes of intervening gas and dust. however, combinations of various qso samples obtained at different times and with different instruments so as to expand a composite and to cover a wider rest frame wavelength region may create systematic effects, and the contribution from qso hosts may contaminate the composite. we have constructed a composite spectrum from luminous blue qsos at 1 < z < 2.1 selected from the sloan digital sky survey (sdss). the observations with x-shooter simultaneously cover ultraviolet (uv) to near-infrared (nir) light, which ensures that the composite spectrum covers the full rest-frame range from lyβ to 11 350 å without any significant host contamination. assuming a power-law continuum for the composite we find a spectral slope of αλ = 1.70 ± 0.01, which is steeper than previously found in the literature. we attribute the differences to our broader spectral wavelength coverage, which allows us to effectively avoid fitting any regions that are affected either by strong qso emissions lines (e.g., balmer lines and complex [fe ii] blends) or by intrinsic host galaxy emission. finally, we demonstrate the application of the qso composite spectrum for evaluating the reddening in other qsos. based on observations made with telescopes at the european southern observatory at la silla/paranal, chile under program 090.a-0147(a).the quasar composite 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/585/a87 source code and composite is also made public at https://github.com/jselsing/quasarcomposite | an x-shooter composite of bright 1 < z < 2 quasars from uv to infrared |
recent data released by james webb space telescope (jwst) and, somewhat earlier, the data presented by hubble space telescope (hst) are commonly understood as a strong indication for breaking of the canonical $\lambda$cdm cosmology. it is argued in the presented work that massive primordial black holes (pbh) could seed galaxy and quasar formation in the very young universe as it has been conjectured in our paper of 1993 and resolve the tension induced by the jwst and the hst data with the standard cosmology. this point of view is presently supported by several recent works. the proposed mechanism of pbh formation leads to the log-normal mass spectrum of pbhs and predicts abundant antimatter population of our galaxy, milky way. both these predictions are in excellent agreement with astronomical observations. | tension between hst/jwst and $\\lambda$cdm cosmology, pbh, and antimatter in the galaxy |
we investigate the steady spherically symmetric accretion in the combined potential of a central black hole and a dark matter halo. for the halo, we consider a hernquist and an nfw potential and calculate the critical points of the flow. we find that the trans-sonic solution to the centre is not possible without a black hole, whereas two types of trans-sonic solutions are possible in its presence. we also derive the mass accretion rate for a black hole at the centre of a dark matter halo. our results indicate two phases of accretion. the first is an initial phase with a low accretion rate that depends on the black hole mass, followed by a second phase with a high accretion rate that depends on the halo mass. in the second phase, the black hole mass increases rapidly to supermassive scales, which explains the existence of quasars at redshift $z\ge 6$ and also the recently detected supermassive black hole (smbh) by the james webb space telescope (jwst). further, we calculate the evolution of the eddington ratio for growing black holes. the accretion is mostly sub-eddington except for a short super-eddington episode when the mass accretion rate transitions from low to high. however, during that episode, the black hole mass is likely inadequate to hinder accretion through radiative feedback. | the origin of supermassive black holes at cosmic dawn |
we present an empirical analysis of the properties of dust-continuum emission in a sample of 17 galaxies in the early universe (4 < z < 8) with well-sampled far-infrared spectral energy distributions (seds) compiled from the literature. we place our results into context by self-consistently comparing to samples of nearby star-forming galaxies, luminous infrared galaxies (lirgs), and quasars. with the exception of two sources, we find no significant evolution in the dust emissivity index across cosmic time, measuring a consistent value of βir = 1.8 ± 0.3 at z > 4, suggesting that the effective dust properties do not change dramatically for most galaxies. despite having comparable stellar masses, we find the high-redshift galaxies to be similar to, or even more extreme than, lirgs in the herschel (u)lirg survey, where (u)lirg refers to (ultra-)lirg, sample in terms of dust temperature ($t_\text{dust} \gt 40 \, \mathrm{k}$) and infrared (ir) luminosity ($l_\text{ir} \gt 10^{11} \, \mathrm{l_\odot }$). we find that the dust temperature evolves mildly towards high redshift, though the lirgs and quasars exhibit elevated temperatures indicating a more efficient and/or additional heating mechanism. where available, we compare stellar mass estimates to our inferred dust masses, whose degeneracy with dust temperature can only be mitigated with a well-constrained sed. in merely half of the cases, the dust yield may be explained by supernovae alone, with four sources ($44{{\ \rm per\ cent}}$) significantly exceeding a highly optimistic yield where mdust ≈ 0.01m*. we discuss possible explanations for this apparent inconsistency and potential observational biases in the measurements of the dust properties of high-redshift galaxies, including in the current ir-bright sample. | an empirical study of dust properties at the earliest epochs |
the apparent position of jet base (core) in radio-loud active galactic nuclei changes with frequency because of synchrotron self-absorption. studying this `core shift' effect enables us to reconstruct properties of the jet regions close to the central engine. we report here results from core shift measurements in agns observed with global vlbi at 2 and 8 ghz at epochs from 1994 to 2016. our sample contains 40 objects observed at least 10 times during that period. the core shift is determined using a new automatic procedure introduced to minimize possible biases. the resulting multiple epoch measurements of the core position are employed for examining temporal variability of the core shift. we argue that the core shift variability is a common phenomenon, as established for 33 of 40 agns we study. our analysis shows that the typical offsets between the core positions at 2 and 8 ghz are about 0.5 mas and they vary in time. typical variability of the individual core positions is about 0.3 mas. the measurements show a strong dependence between the core position and its flux density, suggesting that changes in both are likely related to the nuclear flares injecting denser plasma into the flow. we determine that density of emitting relativistic particles significantly increases during these flares, while relative magnetic field changes less and in the opposite direction. | significant core shift variability in parsec-scale jets of active galactic nuclei |
stream-stream collisions play an important role in the circularization of highly eccentric streams that result from tidal disruption events (tdes). we perform three-dimensional radiation hydrodynamic simulations to show that stream collisions can contribute significant optical and ultraviolet light to the flares produced by tdes, and can explain the majority of the observed emission. our simulations focus on the region near the radiation-pressure-dominated shock produced by a collision and track how the kinetic energy of the stream is dissipated by the associated shock. when the mass flow rate of the stream \dot{m} is a significant fraction of the eddington accretion rate, ≳2% of the initial kinetic energy is converted to radiation as a result of the collision. in this regime, the collision redistributes the specific kinetic energy into the downstream gas and more than 16% of the mass can become unbound. the fraction of unbound gas decreases rapidly as \dot{m} drops significantly below the eddington limit, with no unbound gas being produced when \dot{m} drops to 1% of eddington; we find, however, that the radiative efficiency increases slightly to ≲8% in these cases of low \dot{m}. the effective radiation temperature and size of the photosphere are determined by the stream velocity and \dot{m}, and we find them to be a few times 104 k and 1014 cm in our calculations, comparable to the values inferred for some tde candidates. the size of the photosphere is directly proportional to \dot{m}, which can explain its rapidly changing size as seen in tde candidates such as ps1-10jh. | prompt radiation and mass outflows from the stream-stream collisions of tidal disruption events |
in the light of the recent planck downward revision of the electron scattering optical depth, and of the discovery of a faint active galactic nuclei (agn) population at z > 4, we reassess the actual contribution of quasars to cosmic reionization. to this aim, we extend our previous markov chain monte carlo based data-constrained semi-analytic reionization model and study the role of quasars on global reionization history. we find that the quasars can alone reionize the universe only for models with very high agn emissivities at high redshift. these models are still allowed by the recent cosmic microwave background data and most of the observations related to h i reionization. however, they predict an extended and early he ii reionization ending at z ≳ 4 and a much slower evolution in the mean he ii ly-α forest opacity than what the actual observation suggests. thus, when we further constrain our model against the he ii ly-α forest data, this agn-dominated scenario is found to be clearly ruled out at 2σ limits. the data seems to favour a standard two-component picture where quasar contributions become negligible at z ≳ 6 and a non-zero escape fraction of ∼ 10 per cent is needed from early-epoch galaxies. for such models, mean neutral hydrogen fraction decreases to ∼10-4 at z = 6.2 from ∼0.8 at z = 10.0 and helium becomes doubly ionized at much later time, z ∼ 3. we find that these models are as well in good agreement with the observed thermal evolution of igm as opposed to models with very high agn emissivities. | cosmic reionization after planck ii: contribution from quasars |
we present results from a spectroscopic survey of z ∼ 5 quasars in the cfht legacy survey. using both optical color selection and a likelihood method, we select 97 candidates over an area of 105 deg2 to a limit of i ab < 23.2, and 7 candidates in the range 23.2 < i ab < 23.7 over an area of 18.5 deg2. spectroscopic observations for 43 candidates were obtained with gemini, mmt, and large binocular telescope, of which 37 are z > 4 quasars. this sample extends measurements of the quasar luminosity function ∼1.5 mag fainter than our previous work in sloan digital sky survey stripe 82. the resulting luminosity function is in good agreement with our previous results, and suggests that the faint end slope is not steep. we perform a detailed examination of our survey completeness, particularly the impact of the lyα emission assumed in our quasar spectral models, and find hints that the observed lyα emission from faint z ∼ 5 quasars is weaker than for z ∼ 3 quasars at a similar luminosity. our results strongly disfavor a significant contribution of faint quasars to the hydrogen-ionizing background at z = 5. | the faint end of the z = 5 quasar luminosity function from the cfhtls |
we use vlti/gravity near-infrared interferometry measurements of eight bright type 1 agn to study the size and structure of hot dust that is heated by the central engine. we partially resolve each source, and report gaussian full width at half-maximum sizes in the range 0.3-0.8 mas. in all but one object, we find no evidence for significant elongation or asymmetry (closure phases ≲1°). the narrow range of measured angular sizes is expected given the similar optical flux of our targets, and implies an increasing effective physical radius with bolometric luminosity, as found from previous reverberation and interferometry measurements. the measured sizes for seyfert galaxies are systematically larger than for the two quasars in our sample when measured relative to the previously reported r ∼ l1/2 relationship, which is explained by emission at the sublimation radius. this could be evidence of an evolving near-infrared emission region structure as a function of central luminosity. | the resolved size and structure of hot dust in the immediate vicinity of agn |
we introduce a sub-grid force correction term to better model the dynamical friction experienced by a supermassive black hole (smbh) as it orbits within its host galaxy. this new approach accurately follows an smbh's orbital decay and drastically improves over commonly used `advection' methods. the force correction introduced here naturally scales with the force resolution of the simulation and converges as resolution is increased. in controlled experiments, we show how the orbital decay of the smbh closely follows analytical predictions when particle masses are significantly smaller than that of the smbh. in a cosmological simulation of the assembly of a small galaxy, we show how our method allows for realistic black hole orbits. this approach overcomes the limitations of the advection scheme, where black holes are rapidly and artificially pushed towards the halo centre and then forced to merge, regardless of their orbits. we find that smbhs from merging dwarf galaxies can spend significant time away from the centre of the remnant galaxy. improving the modelling of smbh orbital decay will help in making robust predictions of the growth, detectability and merger rates of smbhs, especially at low galaxy masses or at high redshift. | off the beaten path: a new approach to realistically model the orbital decay of supermassive black holes in galaxy formation simulations |
this is the second in a series of papers aiming to test how the mass (mbh), accretion rate (ṁ) and spin (a*) of supermassive black holes (smbhs) determine the observed properties of type i active galactic nuclei (agn). our project utilizes a sample of 39 unobscured agn at z ≃ 1.55 observed by very large telescope/x-shooter, selected to map a large range in mbh and l/ledd and covers the most prominent uv-optical (broad) emission lines, including hα, hβ, mg ii λ2798 and c iv λ1549. this paper focuses on single-epoch, `virial' mbh determinations from broad emission lines and examines the implications of different continuum modelling approaches in line width measurements. we find that using a local power-law continuum instead of a physically motivated thin disc continuum leads to only slight underestimation of the full width at half-maximum (fwhm) of the lines and the associated mbh(fwhm). however, the line dispersion σline and associated mbh(σline) are strongly affected by the continuum placement and provides less reliable mass estimates than fwhm-based methods. our analysis shows that hα, hβ and mg ii can be safely used for virial mbh estimation. the c iv line, on the other hand, is not reliable in the majority of the cases; this may indicate that the gas emitting this line is not virialized. while hα and hβ show very similar line widths, the mean fwhm(mg ii) is about 30 per cent narrower than fwhm(hβ). we confirm several recent suggestions to improve the accuracy in c iv-based mass estimates, relying on other uv emission lines. such improvements do not reduce the scatter between c iv-based and balmer-line-based mass estimates. | active galactic nuclei at z ∼ 1.5 - ii. black hole mass estimation by means of broad emission lines |
based on spectroscopy and multiband wide-field observations of the gravitationally lensed quasar he 0435-1223, we determine the probability distribution function of the external convergence κext for this system. we measure the under/overdensity of the line of sight towards the lens system and compare it to the average line of sight throughout the universe, determined by using the cfhtlens (the canada france hawaii lensing survey) as a control field. aiming to constrain κext as tightly as possible, we determine under/overdensities using various combinations of relevant informative weighting schemes for the galaxy counts, such as projected distance to the lens, redshift and stellar mass. we then convert the measured under/overdensities into a κext distribution, using ray-tracing through the millennium simulation. we explore several limiting magnitudes and apertures, and account for systematic and statistical uncertainties relevant to the quality of the observational data, which we further test through simulations. our most robust estimate of κext has a median value κ^med_ext = 0.004 and a standard deviation σκ = 0.025. the measured σκ corresponds to 2.5 per cent relative uncertainty on the time delay distance, and hence the hubble constant h0 inferred from this system. the median κ^med_ext value varies by ∼0.005 with the adopted aperture radius, limiting magnitude and weighting scheme, as long as the latter incorporates galaxy number counts, the projected distance to the main lens and a prior on the external shear obtained from mass modelling. this corresponds to just ∼0.5 per cent systematic impact on h0. the availability of a well-constrained κext makes he 0435-1223 a valuable system for measuring cosmological parameters using strong gravitational lens time delays. | h0licow - iii. quantifying the effect of mass along the line of sight to the gravitational lens he 0435-1223 through weighted galaxy counts★ |
we use a sample of powerful $z\, \approx \, 0.1$ type 2 quasars ('obscured'; log [lagn/erg s $^{-1}]\, \gtrsim \, 45$ ), which host kpc-scale ionized outflows and jets, to identify possible signatures of agn feedback on the total molecular gas reservoirs of their host galaxies. specifically, we present atacama pathfinder experiment (apex) observations of the co(2-1) transition for nine sources and the co(6-5) for a subset of three. we find that the majority of our sample reside in starburst galaxies (average specific star formation rates - ssfr - of 1.7 gyr-1), with the seven co-detected quasars also having large molecular gas reservoirs (average mgas = 1.3 × 1010 m⊙), even though we had no pre-selection on the star formation or molecular gas properties. despite the presence of quasars and outflows, we find that the molecular gas fractions (mgas/m⋆ = 0.1-1.2) and depletion times (mgas/sfr = 0.16-0.95 gyr) are consistent with those expected for the overall galaxy population with matched stellar masses and ssfrs. furthermore, for at least two of the three targets with the required measurements, the co(6-5)/co(2-1) emission-line ratios are consistent with star formation dominating the co excitation over this range of transitions. the targets in our study represent a gas-rich phase of galaxy evolution with simultaneously high levels of star formation and nuclear activity; furthermore, the jets and outflows do not have an immediate appreciable impact on the global molecular gas reservoirs. | high molecular gas content and star formation rates in local galaxies that host quasars, outflows, and jets |
the extents of proximity zones of high-redshift quasars enable constraints on the timescales of quasar activity, which are fundamental for understanding the growth of the supermassive black holes (smbhs) that power the quasars' emission. in this study, we obtain precise estimates for the ultraviolet (uv) luminous lifetimes of 10 quasars at 5.8 < z < 6.5. these objects were preselected to have short lifetimes based on preliminary measurements of their proximity zone sizes and were then targeted for high-quality follow-up submillimeter, optical, and infrared observations required to increase the measurements' precision and securely determine their lifetimes. by comparing these proximity zone sizes to mock quasar spectra generated from radiative transfer simulations at a range of different lifetimes, we deduce extremely short lifetimes tq < 104 yr for four objects in our sample, whereas the remaining quasars are consistent with longer lifetimes of tq ≳ 105 yr. these young objects with small proximity zones represent ≲10% of the quasar population as a whole. we compare our results in detail to other studies on timescales of quasar activity, which point toward an average lifetime of tq ~ 106 yr for the quasar population. this is consistent with finding newly turned-on quasars approximately ~1%-10% of the time. these young quasars represent a unique opportunity to study triggering and feedback mechanisms of smbhs, since the onset of their uv-luminous quasar phase happened only recently, and therefore traces of this process might still be observable. | detecting and characterizing young quasars. ii. four quasars at z 6 with lifetimes < 104 yr |
the gamma-ray emission in broad-line blazars is generally explained as inverse compton (ic) radiation of relativistic electrons in the jet scattering optical-uv photons from the broad-line region (blr), the so-called blr external compton (ec) scenario. we test this scenario on the fermi gamma-ray spectra of 106 broad-line blazars detected with the highest significance or largest blr, by looking for cut-off signatures at high energies compatible with γ-γ interactions with blr photons. we do not find evidence for the expected blr absorption. for 2/3 of the sources, we can exclude any significant absorption (τmax < 1), while for the remaining 1/3 the possible absorption is constrained to be 1.5-2 orders of magnitude lower than expected. this result holds also dividing the spectra in high- and low-flux states, and for powerful blazars with large blr. only 1 object out of 10 seems compatible with substantial attenuation (τmax > 5). we conclude that for 9 out of 10 objects, the jet does not interact with blr photons. gamma-rays seem either produced outside the blr most of the time, or the blr is ∼100 × larger than given by reverberation mapping. this means that (i) ec on blr photons is disfavoured as the main gamma-ray mechanism, versus ic on ir photons from the torus or synchrotron self-compton; (ii) the fermi gamma-ray spectrum is mostly intrinsic, determined by the interaction of the particle distribution with the seed-photon spectrum; and (iii) without suppression by the blr, broad-line blazars can become copious emitters above 100 gev, as demonstrated by 3c 454.3. we expect the cta sky to be much richer of broad-line blazars than previously thought. | on the origin of gamma-rays in fermi blazars: beyondthe broad-line region |
periodically variable quasars have been suggested as close binary supermassive black holes. we present a systematic search for periodic light curves in 625 spectroscopically confirmed quasars with a median redshift of 1.8 in a 4.6 deg2 overlapping region of the dark energy survey supernova (des-sn) fields and the sloan digital sky survey stripe 82 (sdss-s82). our sample has a unique 20-yr long multicolour (griz) light curve enabled by combining des-sn y6 observations with archival sdss-s82 data. the deep imaging allows us to search for periodic light curves in less luminous quasars (down to r ~23.5 mag) powered by less massive black holes (with masses ≳ 108.5m⊙) at high redshift for the first time. we find five candidates with significant (at >99.74 per cent single-frequency significance in at least two bands with a global p-value of ~7 × 10-4-3 × 10-3 accounting for the look-elsewhere effect) periodicity with observed periods of ~3-5 yr (i.e. 1-2 yr in rest frame) having ~4-6 cycles spanned by the observations. if all five candidates are periodically variable quasars, this translates into a detection rate of ${\sim }0.8^{+0.5}_{-0.3}$ per cent or ${\sim }1.1^{+0.7}_{-0.5}$ quasar per deg2. our detection rate is 4-80 times larger than those found by previous searches using shallower surveys over larger areas. this discrepancy is likely caused by differences in the quasar populations probed and the survey data qualities. we discuss implications on the future direct detection of low-frequency gravitational waves. continued photometric monitoring will further assess the robustness and characteristics of these candidate periodic quasars to determine their physical origins. | candidate periodically variable quasars from the dark energy survey and the sloan digital sky survey |
cosmological simulations suggest a strong correlation between high optical-depth lyα absorbers, which arise from the intergalactic medium, and 3d mass overdensities on scales of 10-30 {h}-1 comoving mpc. by examining the absorption spectra of ∼80,000 qso sight lines over a volume of 0.1 gpc3 in the sloan digital sky survey iii (sdss-iii), we have identified an extreme overdensity, boss1441, which contains a rare group of strong lyα absorbers at z=2.32+/- 0.02. this absorber group is associated with six qsos at the same redshift on a 30 comoving mpc scale. using mayall/mosaic narrowband and broadband imaging, we detect lyα emitters (laes) down to 0.7× {l}{lyα }*and reveal a large-scale structure of laes in this field. our follow-up lbt observations have spectroscopically confirmed 20 galaxies in the density peak. we show that boss1441 has an lae overdensity of 10.8 ± 2.6 on a 15 comoving mpc scale, which could collapse to a massive cluster with m ≳ 1015 {m}⊙at z∼ 0. this overdensity is among the most massive large-scale structures at z∼ 2 discovered to date. | mapping the most massive overdensities through hydrogen (mammoth). ii. discovery of the extremely massive overdensity boss1441 at z = 2.32 |
we survey the properties of stars destroyed in tidal disruption events (tdes) as a function of black hole (bh) mass, stellar mass and evolutionary state, star formation history and redshift. for m_{bh} ≲ 10^7 m_{⊙}, the typical tde is due to a m* ∼ 0.3 m⊙ m-dwarf, although the mass function is relatively flat for m_{ast } ≲ m_{⊙}. the contribution from older main-sequence stars and sub-giants is small but not negligible. from mbh ≃ 107.5-108.5 m⊙, the balance rapidly shifts to higher mass stars and a larger contribution from evolved stars, and is ultimately dominated by evolved stars at higher bh masses. the star formation history has little effect until the rates are dominated by evolved stars. tde rates should decline very rapidly towards higher redshifts. the volumetric rate of tdes is very high because the bh mass function diverges for low masses. however, any emission mechanism which is largely eddington-limited for low bh masses suppresses this divergence in any observed sample and leads to tde samples dominated by mbh ≃ 106.0-107.5 m⊙ bhs with roughly eddington peak accretion rates. the typical fall-back time is relatively long, with 16 per cent having tfb < 10-1 yr (37 d), and 84 per cent having longer time-scales. many residual rate discrepancies can be explained if surveys are biased against tdes with these longer tfb, which seems very plausible if tfb has any relation to the transient rise time. for almost any bh mass function, systematic searches for fainter, faster time-scale tdes in smaller galaxies, and longer time-scale tdes in more massive galaxies are likely to be rewarded. | tidal disruption event demographics |
we measure the two-point clustering of spectroscopically confirmed quasars from the final sample of the baryon oscillation spectroscopic survey (boss) on comoving scales of 4 ≲ s ≲ 22 h-1 mpc. the sample covers 6950 deg2 [ ∼ 19 (h- 1gpc)3] and, over the redshift range 2.2 ≤ z ≤ 2.8, contains 55 826 homogeneously selected quasars, which is twice as many as in any similar work. we deduce bq = 3.54 ± 0.10; the most precise measurement of quasar bias to date at these redshifts. this corresponds to a host halo mass of ∼2 × 1012 h-1 m⊙ with an implied quasar duty cycle of ∼1 per cent. the real-space projected correlation function is well fitted by a power law of index 2 and correlation length r0 = (8.12 ± 0.22) h- 1 mpc over scales of 4 ≲ rp ≲ 25 h-1 mpc. to better study the evolution of quasar clustering at moderate redshift, we extend the redshift range of our study to z ∼ 3.4 and measure the bias and correlation length of three subsamples over 2.2 ≤ z ≤ 3.4. we find no significant evolution of r0 or bias over this range, implying that the host halo mass of quasars decreases somewhat with increasing redshift. we find quasar clustering remains similar over a decade in luminosity, contradicting a scenario in which quasar luminosity is monotonically related to halo mass at z ≈ 2.5. our results are broadly consistent with previous boss measurements, but they yield more precise constraints based upon a larger and more uniform data set. | clustering of intermediate redshift quasars using the final sdss iii-boss sample |
we present a new implementation for active galactic nucleus (agn) feedback through small-scale, ultrafast winds in the moving-mesh hydrodynamic code arepo. the wind is injected by prescribing mass, momentum, and energy fluxes across a spherical boundary centred on a supermassive black hole according to available constraints for accretion disc winds. after sweeping-up a mass equal to their own, small-scale winds thermalize, powering energy-driven outflows with dynamics, structure, and cooling properties in excellent agreement with those of analytic wind solutions. momentum-driven solutions do not easily occur, because the compton cooling radius is usually much smaller than the free-expansion radius of the small-scale winds. through various convergence tests, we demonstrate that our implementation yields wind solutions, which are well converged down to the typical resolution achieved in cosmological simulations. we test our model in hydrodynamic simulations of isolated milky way - mass galaxies. above a critical agn luminosity, initially spherical, small-scale winds power bipolar, energy-driven superwinds that break out of the galactic nucleus, flowing at speeds $\gt 1000 \rm \, km \, s^{-1}$ out to $\sim 10 \, \rm kpc$. these energy-driven outflows result in moderate, but long-term, reduction in star formation, which becomes more pronounced for higher agn luminosities and faster small-scale winds. suppression of star formation proceeds through a rapid mode that involves the removal of the highest density, nuclear gas, and through a slower mode that effectively halts halo gas accretion. our new implementation makes it possible to model agn-driven winds in a physically meaningful and validated way in simulations of galaxy evolution, the interstellar medium and black hole accretion flows. | powering galactic superwinds with small-scale agn winds |
x-ray cavities are key tracers of mechanical (or radio mode) heating arising from the active galactic nuclei (agns) in brightest cluster galaxies (bcgs). we report on a survey for x-ray cavities in 83 massive, high-redshift (0.4\lt z\lt 1.2) clusters of galaxies selected by their sunyaev-zel’dovich signature in the south pole telescope data. based on chandra x-ray images, we find a total of six clusters having symmetric pairs of surface brightness depressions consistent with the picture of radio jets inflating x-ray cavities in the intracluster medium (icm). the majority of these detections are of relatively low significance and require deeper follow-up data in order to be confirmed. further, this search will miss small (<10 kpc) x-ray cavities that are unresolved by chandra at high (z≳ 0.5) redshift. despite these limitations, our results suggest that the power generated by agn feedback in bcgs has remained unchanged for over half of the age of the universe (\gt 7 gyr at z∼ 0.8). on average, the detected x-ray cavities have powers of (0.8-5)× {{10}45} erg {{s}-1}, enthalpies of (3-6)× {{10}59} erg, and radii of ∼17 kpc. integrating over 7 gyr, we find that the supermassive black holes in bcgs may have accreted 108 to several {{10}9} {{m}⊙ } of material to power these outflows. this level of accretion indicates that significant supermassive black hole growth may occur not only at early times, in the quasar era, but at late times as well. we also find that x-ray cavities at high redshift may inject an excess heat of 0.1-1.0 kev per particle into the hot icm above and beyond the energy needed to offset cooling. although this result needs to be confirmed, we note that the magnitude of excess heating is similar to the energy needed to preheat clusters, break self-similarity, and explain the excess entropy in hot atmospheres. | x-ray cavities in a sample of 83 spt-selected clusters of galaxies: tracing the evolution of agn feedback in clusters of galaxies out to z=1.2 |
galaxy interactions are thought to be one of the main triggers of active galactic nuclei (agn), especially at high luminosities, where the accreted gas mass during the agn lifetime is substantial. evidence for a connection between mergers and agn, however, remains mixed. possible triggering mechanisms remain particularly poorly understood for luminous agn, which are thought to require triggering by major mergers, rather than secular processes. we analyse the host galaxies of a sample of 20 optically and x-ray selected luminous agn (log(lbol [erg s-1]) > 45) at z ∼ 0.6 using hubble space telescope wide field camera 3 data in the f160w/h band. 15/20 sources have resolved host galaxies. we create a control sample of mock agn by matching the agn host galaxies to a control sample of non-agn galaxies. visual signs of disturbances are found in about 25 per cent of sources in both the agn hosts and control galaxies. using both visual classification and quantitative morphology measures, we show that the levels of disturbance are not enhanced when compared to a matched control sample. we find no signs that major mergers play a dominant role in triggering agn at high luminosities, suggesting that minor mergers and secular processes dominate agn triggering up to the highest agn luminosities. the upper limit on the enhanced fraction of major mergers is ≤20 per cent. while major mergers might increase the incidence of luminous agn, they are not the prevalent triggering mechanism in the population of unobscured agn. | host galaxies of luminous z ∼ 0.6 quasars: major mergers are not prevalent at the highest agn luminosities |
we present the luminosity function of z ∼ 4 quasars based on the hyper suprime-cam subaru strategic program wide layer imaging data in the g, r, i, z, and y bands covering 339.8 deg2. from stellar objects, 1666 z ∼ 4 quasar candidates are selected via the g-dropout selection down to i = 24.0 mag. their photometric redshifts cover the redshift range between 3.6 and 4.3, with an average of 3.9. in combination with the quasar sample from the sloan digital sky survey in the same redshift range, a quasar luminosity function covering the wide luminosity range of m1450 = -22 to -29 mag is constructed. the quasar luminosity function is well described by a double power-law model with a knee at m1450 = -25.36 ± 0.13 mag and a flat faint-end slope with a power-law index of -1.30 ± 0.05. the knee and faint-end slope show no clear evidence of redshift evolution from those seen at z ∼ 2. the flat slope implies that the uv luminosity density of the quasar population is dominated by the quasars around the knee, and does not support the steeper faint-end slope at higher redshifts reported at z > 5. if we convert the m1450 luminosity function to the hard x-ray 2-10 kev luminosity function using the relation between the uv and x-ray luminosity of quasars and its scatter, the number density of uv-selected quasars matches well with that of the x-ray-selected active galactic nuclei (agns) above the knee of the luminosity function. below the knee, the uv-selected quasars show a deficiency compared to the hard x-ray luminosity function. the deficiency can be explained by the lack of obscured agns among the uv-selected quasars. | the quasar luminosity function at redshift 4 with the hyper suprime-cam wide survey |
we present a study of extended galaxy halo gas through h i and o vi absorption over two decades in projected distance at z ≈ 0.2. the study is based on a sample of 95 galaxies from a highly complete (>80 per cent) survey of faint galaxies (l > 0.1l*) with archival quasar absorption spectra and 53 galaxies from the literature. a clear anticorrelation is found between h i (o vi) column density and virial radius normalized projected distance, d/rh. strong h i (o vi) absorption systems with column densities greater than 1014.0 (1013.5) cm-2 are found for 48 of 54 (36 of 42) galaxies at d < rh indicating a mean covering fraction of < κ_{h i} > = 0.89 (< κ_{o vi} > = 0.86). o vi absorbers are found at d ≈ rh, beyond the extent observed for lower ionization species. at d/rh = 1-3 strong h i (o vi) absorption systems are found for only 7 of 43 (5 of 34) galaxies (< κ_{h i} > = 0.16 and < κ_{o vi} > = 0.15). beyond d = 3 rh, the h i and o vi covering fractions decrease to levels consistent with coincidental systems. the high completeness of the galaxy survey enables an investigation of environmental dependence of extended gas properties. galaxies with nearby neighbours exhibit a modest increase in o vi covering fraction at d > rh compared to isolated galaxies (κ_{o vi}≈ 0.13 versus 0.04) but no excess h i absorption. these findings suggest that environmental effects play a role in distributing heavy elements beyond the enriched gaseous haloes of individual galaxies. finally, we find that differential h i and o vi absorption between early- and late-type galaxies continues from d < rh to d ≈ 3 rh. | on the possible environmental effect in distributing heavy elements beyond individual gaseous haloes |
quasars have recently been used as an absolute distance indicator, extending the hubble diagram to high redshift to reveal a deviation from the expansion history predicted for the standard, λ cdm cosmology. here we show that the laser interferometer space antenna (lisa) will efficiently test this claim with standard sirens at high redshift, defined by the coincident gravitational wave (gw) and electromagnetic (em) observations of the merger of massive black hole binaries (mbhbs). assuming a fiducial λ cdm cosmology for generating mock standard siren data sets, the evidence for the λ cdm model with respect to an alternative model inferred from quasar data is investigated. by simulating many realizations of possible future lisa observations, we find that for 50% of these realizations (median result) four mbhb standard siren measurements will suffice to strongly differentiate between the two models, while 14 standard sirens will yield a similar result in 95% of the realizations. in addition, we investigate the measurement precision of cosmological parameters as a function of the number of observed lisa mbhb standard sirens, finding that 15 events will on average achieve a relative precision of 5% for h0, reducing to 3% and 2% with 25 and 40 events, respectively. our investigation clearly highlights the potential of lisa as a cosmological probe able to accurately map the expansion of the universe at z ≳2 , and as a tool to cross-check and cross-validate cosmological em measurements with complementary gw observations. | testing the quasar hubble diagram with lisa standard sirens |
we present a new measurement of the systemic proper motion of the small magellanic cloud (smc), based on an expanded set of 30 fields containing background quasars and spanning a ∼3 year baseline, using the hubble space telescope (hst) wide field camera 3. combining this data with our previous five hst fields, and an additional eight measurements from the gaia-tycho astrometric solution catalog, brings us to a total of 43 smc fields. we measure a systemic motion of μw= -0.82 ± 0.02 (random) ± 0.10 (systematic) mas yr-1 and μn= -1.21 ± 0.01 (random) ± 0.03 (systematic) mas yr-1. after subtraction of the systemic motion, we find little evidence for rotation, but find an ordered mean motion radially away from the smc in the outer regions of the galaxy, indicating that the smc is in the process of tidal disruption. we model the past interactions of the clouds with each other based on the measured present-day relative velocity between them of 103 ± 26 km s-1. we find that in 97% of our considered cases, the clouds experienced a direct collision 147 ± 33 myr ago, with a mean impact parameter of 7.5 ± 2.5 kpc. | the proper motion field of the small magellanic cloud: kinematic evidence for its tidal disruption |
oj 287 is a quasi-periodic quasar with roughly 12 year optical cycles. it displays prominent outbursts that are predictable in a binary black hole model. the model predicted a major optical outburst in 2015 december. we found that the outburst did occur within the expected time range, peaking on 2015 december 5 at magnitude 12.9 in the optical r-band. based on swift/xrt satellite measurements and optical polarization data, we find that it included a major thermal component. its timing provides an accurate estimate for the spin of the primary black hole, χ =0.313+/- 0.01. the present outburst also confirms the established general relativistic properties of the system such as the loss of orbital energy to gravitational radiation at the 2% accuracy level, and it opens up the possibility of testing the black hole no-hair theorem with 10% accuracy during the present decade. | primary black hole spin in oj 287 as determined by the general relativity centenary flare |
context. before the publication of the gaia catalogue, the contents of the first data release have undergone multiple dedicated validation tests.aims: these tests aim to provide in-depth analysis of the catalogue content in order to detect anomalies and individual problems in specific objects or in overall statistical properties, and either to filter them before the public release or to describe the different caveats on the release for an optimal exploitation of the data.methods: dedicated methods using either gaia internal data, external catalogues, or models have been developed for the validation processes. they test normal stars as well as various populations such as open or globular clusters, double stars, variable stars, and quasars. properties of coverage, accuracy, and precision of the data are provided by the numerous tests presented here and are jointly analysed to assess the data release content.results: this independent validation confirms the quality of the published data, gaia dr1 being the most precise all-sky astrometric and photometric catalogue to date. however, several limitations in terms of completeness, and astrometric or photometric quality are identified and described. figures describing the relevant properties of the release are shown, and the testing activities carried out validating the user interfaces are also described. a particular emphasis is made on the statistical use of the data in scientific exploitation. | gaia data release 1. catalogue validation |
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