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despite efforts over several decades, direct-detection experiments have not yet led to the discovery of the dark matter (dm) particle. this has led to increasing interest in alternatives to the lambda cdm (lcdm) paradigm and alternative dm scenarios (including fuzzy dm, warm dm, self-interacting dm, etc.). in many of these scenarios, dm particles cannot be detected directly and constraints on their properties can only be arrived at using astrophysical observations. the dark energy spectroscopic instrument (desi) is currently one of the most powerful instruments for wide-field surveys. the synergy of desi with esa's gaia satellite and future observing facilities will yield datasets of unprecedented size and coverage that will enable constraints on dm over a wide range of physical and mass scales and across redshifts. desi will obtain spectra of the lyman-alpha forest out to z~5 by detecting about 1 million qso spectra that will put constraints on clustering of the low-density intergalactic gas and dm halos at high redshift. desi will obtain radial velocities of 10 million stars in the milky way (mw) and local group satellites enabling us to constrain their global dm distributions, as well as the dm distribution on smaller scales. the paradigm of cosmological structure formation has been extensively tested with simulations. however, the majority of simulations to date have focused on collisionless cdm. simulations with alternatives to cdm have recently been gaining ground but are still in their infancy. while there are numerous publicly available large-box and zoom-in simulations in the lcdm framework, there are no comparable publicly available wdm, sidm, fdm simulations. doe support for a public simulation suite will enable a more cohesive community effort to compare observations from desi (and other surveys) with numerical predictions and will greatly impact dm science. | snowmass2021 cosmic frontier white paper: prospects for obtaining dark matter constraints with desi |
we study the relation between obscuration and supermassive black hole (smbh) accretion using a large sample of hard x-ray selected active galactic nuclei (agns). we find a strong decrease in the fraction of obscured sources above the eddington limit for dusty gas ( $\mathrm{log}{\lambda }_{\mathrm{edd}}\gtrsim -2$ ) confirming earlier results, and consistent with the radiation-regulated unification model. this also explains the difference in the eddington ratio distribution functions (erdfs) of type 1 and type 2 agns obtained by a recent study. the break in the erdf of nearby agns is at $\mathrm{log}{\lambda }_{\mathrm{edd}}^{* }=-1.34\,\pm \,0.07$ . this corresponds to the λ edd where agns transition from having most of their sky covered by obscuring material to being mostly devoid of absorbing material. a similar trend is observed for the luminosity function, which implies that most of the smbh growth in the local universe happens when the agn is covered by a large reservoir of gas and dust. these results could be explained with a radiation-regulated growth model, in which agns move in the n h-λ edd plane during their life cycle. the growth episode starts with the agn mostly unobscured and accreting at low λ edd. as the smbh is further fueled, λ edd, n h and the covering factor increase, leading the agn to be preferentially observed as obscured. once λ edd reaches the eddington limit for dusty gas, the covering factor and n h rapidly decrease, leading the agn to be typically observed as unobscured. as the remaining fuel is depleted, the smbh goes back into a quiescent phase. | bass xxxvii: the role of radiative feedback in the growth and obscuration properties of nearby supermassive black holes |
we present the discovery of pso j030947.49+271757.31, the radio brightest (23.7 mjy at 1.4 ghz) active galactic nucleus (agn) at z > 6.0. it was selected by cross-matching the nrao vla sky survey and the panoramic survey telescope and rapid response system ps1 databases and its high-z nature was confirmed by a dedicated spectroscopic observation at the large binocular telescope. a pointed neil gehrels swift observatory xrt observation allowed us to measure a flux of ∼3.4 × 10-14 erg s-1 cm-2 in the [0.5-10] kev energy band, which also makes this object the x-ray brightest agn ever observed at z > 6.0. its flat radio spectrum (ανr < 0.5), very high radio loudness (r > 103), and strong x-ray emission, compared to the optical, support the hypothesis of the blazar nature of this source. assuming that this is the only blazar at this redshift in the surveyed area of sky, we derive a space density of blazars at z ∼ 6 and with m1450 å < -25.1 of 5.5+11.2-4.6 × 10-3 gpc-3. from this number, and assuming a reasonable value of the bulk velocity of the jet (γ = 10), we can also infer a space density of the entire radio-loud agn population at z ∼ 6 with the same optical/uv absolute magnitude of 1.10+2.53-0.91 gpc-3. larger samples of blazars will be necessary to better constrain these estimates. | the first blazar observed at z > 6 |
results from a few decades of reverberation mapping (rm) studies have revealed a correlation between the radius of the broad-line emitting region (blr) and the continuum luminosity of active galactic nuclei. this "radius-luminosity" relation enables survey-scale black hole mass estimates across cosmic time, using relatively inexpensive single-epoch spectroscopy, rather than intensive rm time monitoring. however, recent results from newer rm campaigns challenge this widely used paradigm, reporting quasar blr sizes that differ significantly from the previously established radius-luminosity relation. using simulations of the radius-luminosity relation with the observational parameters of the sloan digital sky survey reverberation mapping (sdss-rm) project, we find that this difference is not likely due to observational biases. instead, it appears that previous rm samples were biased to a subset of quasar properties, and the broader parameter space occupied by the sdss-rm quasar sample has a genuinely wider range of blr sizes. we examine the correlation between the deviations from the radius-luminosity relation and several quasar parameters; the most significant correlations indicate that the deviations depend on the uv/optical spectral energy distribution and the relative amount of ionizing radiation. our results indicate that single-epoch black hole mass estimates that do not account for the diversity of quasars in the radius-luminosity relation could be overestimated by an average of ∼0.3 dex. | the sloan digital sky survey reverberation mapping project: the hβ radius-luminosity relation |
the ultraviolet background (uvb) emitted by quasars and galaxies governs the ionization and thermal state of the intergalactic medium (igm), regulates the formation of high-redshift galaxies, and is thus a key quantity for modeling cosmic reionization. the vast majority of cosmological hydrodynamical simulations implement the uvb via a set of spatially uniform photoionization and photoheating rates derived from uvb synthesis models. we show that simulations using canonical uvb rates reionize and, perhaps more importantly, spuriously heat the igm, much earlier (z∼ 15) than they should. this problem arises because at z> 6, where observational constraints are nonexistent, the uvb amplitude is far too high. we introduce a new methodology to remedy this issue, and we generate self-consistent photoionization and photoheating rates to model any chosen reionization history. following this approach, we run a suite of hydrodynamical simulations of different reionization scenarios and explore the impact of the timing of reionization and its concomitant heat injection on the thermal state of the igm. we present a comprehensive study of the pressure smoothing scale of igm gas, illustrating its dependence on the details of both hydrogen and helium reionization, and argue that it plays a fundamental role in interpreting lyα forest statistics and the thermal evolution of the igm. the premature igm heating we have uncovered implies that previous work has likely dramatically overestimated the impact of photoionization feedback on galaxy formation, which sets the minimum halo mass able to form stars at high redshifts. we make our new uvb photoionization and photoheating rates publicly available for use in future simulations. | self-consistent modeling of reionization in cosmological hydrodynamical simulations |
we produce simulations of the atomic c ii line emission in large sky fields in order to determine the current and future prospects for mapping this line during the high-redshift epoch of reionization. we calculate the c ii line intensity, redshift evolution, and spatial fluctuations using observational relations between c ii emission and the galaxy star formation rate over the frequency range 200-300 ghz. we estimate an averaged intensity of {i}c\ii=(4+/- 2)× {10}2 {jy} {{sr}}-1 in the redshift range z ∼ 5.3-8.5. observations of the c ii emission in this frequency range will suffer contamination from emission lines at lower redshifts, in particular co rotational lines. using simulations, we estimated the co contamination to be {i}{co}≈ {10}3 {jy} {{sr}}-1 (originating from galaxies at z \lt 2.5). using detailed simulations of the c ii and co emission across a range of redshifts, we generate maps as a function of angle and frequency, fully taking into account this resolution and light-cone effects. in order to reduce the foreground contamination, we find that we should mask galaxies below redshifts ∼2.5 with a co(j:2-1) to co(j:6-5) line flux density higher than 5× {10}-22 w {m}-2 or an ab magnitude lower than {m}k=22. we estimate that the additional continuum contamination originating in emission from stars and in dust, free-free, free-bound, and two-photon emission in the interstellar medium is of the order of {10}5 {jy} {{sr}}-1, which is well above the expected c ii signal. we also consider the possibility of cross-correlating foreground lines with galaxy surveys in order to probe the intensity of the foregrounds. finally, we discuss the expected constraints from two experiments capable of measuring the expected c ii power spectrum. | prospects for detecting c ii emission during the epoch of reionization |
we present a new relationship between central black hole (bh) mass and host galaxy stellar bulge mass extending to the lowest bh masses known in dwarf galaxies (m bh ≲ 105 m ⊙ m ⋆ ∼ 109 m ⊙). we have obtained visible and near-infrared hubble space telescope imaging of seven dwarf galaxies with optically selected broad-line active galactic nuclei (agns) and bh mass estimates from single-epoch spectroscopy. we perform 2d photometric modeling with galfit to decompose the structure of these galaxies and find that the majority have an inner bulge/pseudo-bulge component with an exponential disk that dominates the total stellar mass. using the modeling results and color-dependent mass-to-light ratios, we determine the stellar mass of each photometric component in each galaxy. we determine the m bh-m bulge relation using a total of 12 dwarf galaxies hosting broad-line agns, along with a comparison sample of 88 galaxies with dynamical bh masses and 37 reverberation-mapped agns. we find a strong correlation between bh mass and bulge mass with {log}({m}bh}/{m}⊙ )=(1.24+/- 0.08) {log}({m}bulge}/{10}11{m}⊙ )+(8.80+/- 0.09). the near-linear slope and normalization are in good agreement with correlations found previously when only considering higher-mass systems. this work has quadrupled the number of dwarf galaxies on the bh-bulge mass relation, with implications for bh seeding and predictions for gravitational wave detections of merging bhs at higher redshifts with lisa. | the black hole-bulge mass relation including dwarf galaxies hosting active galactic nuclei |
we report the discovery and spectroscopic confirmation of 22 new gravitationally lensed quasars found using gaia data release 2. the selection was made using several techniques: multiple gaia detections around objects in quasar candidate catalogues, modelling of unwise coadd pixels using gaia astrometry, and gaia detections offset from photometric and spectroscopic galaxies. spectra of 33 candidates were obtained with the william herschel telescope, 22 of which are lensed quasars, two highly probably lensed quasars, five nearly identical quasar pairs, one inconclusive system, and three contaminants. of the three confirmed quadruply imaged systems, j2145+6345 is a 2.1 arcsec separation quad with four bright images (g = 16.86, 17.26, 18.34, 18.56), making it ideal for time delay monitoring. analysing this new sample alongside known lenses in the pan-starrs footprint, and comparing to expected numbers of lenses, we show that, as expected, we are biased towards systems with bright lensing galaxies and low source redshifts. we discuss possible techniques to remove this bias from future searches. a |b| > 20 complete sample of lensed quasars detected by gaia and with image separations above 1 arcsec will provide a valuable statistical sample of around 350 systems. currently only 96 known lenses satisfy these criteria, yet promisingly, our unwise modelling technique is able to recover all of these with simple wise-gaia colour cuts that remove ∼80 per cent of previously followed-up contaminants. finally, we provide an online data base of known lenses, quasar pairs, and contaminant systems. | gravitationally lensed quasars in gaia - iii. 22 new lensed quasars from gaia data release 2 |
x-ray emission from quasars has been detected up to redshift z = 7.5, although only limited to a few objects at z > 6.5. in this work, we present new chandra observations of five z > 6.5 quasars. by combining with archival chandra observations of six additional z > 6.5 quasars, we perform a systematic analysis on the x-ray properties of these earliest accreting supermassive black holes (smbhs). we measure the black hole masses, bolometric luminosities (lbol), eddington ratios (λedd), emission line properties, and infrared luminosities (lir) of these quasars using infrared and submillimeter observations. correlation analysis indicates that the x-ray bolometric correction (the factor that converts from x-ray luminosity to bolometric luminosity) decreases with increasing lbol, and that the uv/optical-to-x-ray ratio, αox, strongly correlates with l2500 å, and moderately correlates with λedd and blueshift of c iv emission lines. these correlations are consistent with those found in lower-z quasars, indicating quasar accretion physics does not evolve with redshift. we also find that lir does not correlate with l2-10 kev in these luminous distant quasars, suggesting that the ratio of the smbh growth rate and their host galaxy growth rate in these early luminous quasars are different from those of local galaxies. a joint spectral analysis of the x-ray detected z > 6.5 quasars yields an average x-ray photon index of ${\rm{\gamma }}={2.32}_{-0.30}^{+0.31}$ , steeper than that of low-z quasars. by comparing it with the γ - λedd relation, we conclude that the steepening of γ for quasars at z > 6.5 is mainly driven by their higher eddington ratios. | revealing the accretion physics of supermassive black holes at redshift z ∼ 7 with chandra and infrared observations |
in this paper, we present a model-independent approach to calibrate the largest quasar sample. calibrating quasar samples is essentially constraining the parameters of the linear relation between the log of the ultraviolet (uv) and x-ray luminosities. this calibration allows quasars to be used as standardized candles. there is a strong correlation between the parameters characterizing the quasar luminosity relation and the cosmological distances inferred from using quasars as standardized candles. we break this degeneracy by using gaussian process regression to model-independently reconstruct the expansion history of the universe from the latest type ia supernova observations. using the calibrated quasar data set, we further reconstruct the expansion history up to redshift of z ~ 7.5. finally, we test the consistency between the calibrated quasar sample and the standard lambda cold dark matter ($\rm {\lambda }cdm$) model based on the posterior probability distribution of the gp hyperparameters. our results show that the quasar sample is in good agreement with the standard $\rm {\lambda }cdm$ model in the redshift range of the supernova, despite the 2-3σ significant deviations taking place at higher redshifts. fitting the standard $\rm {\lambda }cdm$ model to the calibrated quasar sample, we obtain a high value of the matter density parameter $\omega _m = 0.382^{+0.045}_{-0.042}$, which is marginally consistent with the constraints from other cosmological observations. | hubble diagram at higher redshifts: model independent calibration of quasars |
context. sources at the brightest end of the quasi-stellar object (qso) luminosity function, during the peak epoch in the history of star formation and black hole accretion (z ∼ 2-4, often referred to as "cosmic noon") are privileged sites to study the cycle of feeding & feedback processes in massive galaxies.aims: we aim to perform the first systematic study of cold gas properties in the most luminous qsos, by characterising their host-galaxies and environment. these targets exhibit indeed widespread evidence of outflows at nuclear and galactic scales.methods: we analyse alma, noema and jvla observations of the far-infrared continuum, co and [cii] emission lines in eight qsos (bolometric luminosity lbol ≳ 3 × 1047 erg s-1) from the wise-sdss selected hyper-luminous (wissh) qsos sample at z ∼ 2.4-4.7.results: we report a 100% emission line detection rate and a 80% detection rate in continuum emission, and we find co emission to be consistent with the steepest co ladders observed so far. sub-millimetre data reveal presence of (one or more) bright companion galaxies around ∼80% of wissh qsos, at projected distances of ∼6-130 kpc. we observe a variety of sizes for the molecular gas reservoirs (∼1.7-10 kpc), mostly associated with rotating disks with disturbed kinematics. wissh qsos typically show lower co luminosity and higher star formation efficiency than infrared matched, z ∼ 0-3 main-sequence galaxies, implying that, given the observed sfr ∼170-1100 m⊙ yr-1, molecular gas is converted into stars in ≲50 myr. most targets show extreme dynamical to black-hole mass ratios mdyn/mbh ∼ 3-10, two orders of magnitude smaller than local relations. the molecular gas fraction in the host-galaxies of wissh is lower by a factor of ∼10-100 than in star forming galaxies with similar m*.conclusions: our analysis reveals that hyper-luminous qsos at cosmic noon undergo an intense growth phase of both the central super-massive black hole and of the host-galaxy. these systems pinpoint the high-density sites where giant galaxies assemble, where we show that mergers play a major role in the build-up of the final host-galaxy mass. we suggest that the observed low molecular gas fraction and short depletion timescale are due to agn feedback, whose presence is indicated by fast agn-driven ionised outflows in all our targets. | the wissh quasars project. ix. cold gas content and environment of luminous qsos at z ∼ 2.4-4.7 |
we study the optical gri photometric variability of a sample of 190 quasars within the sdss stripe 82 region that have long-term photometric coverage during ~1998-2020 with sdss, panstarrs-1, the dark energy survey, and dedicated follow-up monitoring with blanco 4m/decam. with on average ~200 nightly epochs per quasar per filter band, we improve the parameter constraints from a damped random walk (drw) model fit to the light curves over previous studies with 10-15 yr baselines and ≲ 100 epochs. we find that the average damping time-scale τdrw continues to rise with increased baseline, reaching a median value of ~750 d (g band) in the rest frame of these quasars using the 20-yr light curves. some quasars may have gradual, long-term trends in their light curves, suggesting that either the drw fit requires very long baselines to converge, or that the underlying variability is more complex than a single drw process for these quasars. using a subset of quasars with better-constrained τdrw (less than 20 per cent of the baseline), we confirm a weak wavelength dependence of τdrw∝λ0.51 ± 0.20. we further quantify optical variability of these quasars over days to decades time-scales using structure function (sf) and power spectrum density (psd) analyses. the sf and psd measurements qualitatively confirm the measured (hundreds of days) damping time-scales from the drw fits. however, the ensemble psd is steeper than that of a drw on time-scales less than ~ a month for these luminous quasars, and this second break point correlates with the longer drw damping time-scale. | optical variability of quasars with 20-yr photometric light curves |
we present a description of the australian dark energy survey (ozdes) and summarize the results from its 6 years of operations. using the 2df fibre positioner and aaomega spectrograph on the 3.9-m anglo-australian telescope, ozdes has monitored 771 active galactic nuclei, classified hundreds of supernovae, and obtained redshifts for thousands of galaxies that hosted a transient within the 10 deep fields of the dark energy survey. we also present the second ozdes data release, containing the redshifts of almost 30 000 sources, some as faint as rab = 24 mag, and 375 000 individual spectra. these data, in combination with the time-series photometry from the dark energy survey, will be used to measure the expansion history of the universe out to z ∼ 1.2 and the masses of hundreds of black holes out to z ∼ 4. ozdes is a template for future surveys that combine simultaneous monitoring of targets with wide-field imaging cameras and wide-field multi-object spectrographs. | ozdes multi-object fibre spectroscopy for the dark energy survey: results and second data release |
quasars have been proposed as a new class of standard candles analogous to supernovae, since their large redshift range and high luminosities make them excellent candidates. the reverberation mapping (rm) method enables one to estimate the distance to the source from the time delay measurement of the emission lines with respect to the continuum, since the time delay depends on the absolute luminosity of the source. the radius-luminosity relation exhibits a low scatter and offers a potential use in cosmology. however, in recent years, the inclusion of new sources, particularly the super-eddington accreting qso, has increased the dispersion in the radius-luminosity relation, with many objects showing time delays shorter than the expected. using 117 h β reverberation-mapped active galactic nuclei with 0.002 < z < 0.9 and 41.5 < log l 5100 < 45.9, we find a correction for the time delay based on the dimensionless accretion rate (\dot{{\mathscr{m}}}) considering a virial factor anticorrelated with the fwhm of h β. this correction decreases the scattering of the accretion parameters compared with the typical values used, which is directly reflected by suppressing the radius-luminosity relation dispersion. we also confirm the anticorrelation between the excess of variability and the accretion parameters. with this correction, we are able to build the hubble diagram and estimate the cosmological constants ω mand ωλ, which are consistent with the λ cold dark matter model at 2σ confidence level. therefore, reverberation mapping results can be used to constrain cosmological models in the future. | can reverberation-measured quasars be used for cosmology? |
we present results from the first 12 months of operation of radio galaxy zoo, which upon completion will enable visual inspection of over 170 000 radio sources to determine the host galaxy of the radio emission and the radio morphology. radio galaxy zoo uses 1.4 ghz radio images from both the faint images of the radio sky at twenty centimeters (first) and the australia telescope large area survey (atlas) in combination with mid-infrared images at 3.4 μm from the wide-field infrared survey explorer (wise) and at 3.6 μm from the spitzer space telescope. we present the early analysis of the wise mid-infrared colours of the host galaxies. for images in which there is >75 per cent consensus among the radio galaxy zoo cross-identifications, the project participants are as effective as the science experts at identifying the host galaxies. the majority of the identified host galaxies reside in the mid-infrared colour space dominated by elliptical galaxies, quasi-stellar objects and luminous infrared radio galaxies. we also find a distinct population of radio galaxy zoo host galaxies residing in a redder mid-infrared colour space consisting of star-forming galaxies and/or dust-enhanced non-star-forming galaxies consistent with a scenario of merger-driven active galactic nuclei (agn) formation. the completion of the full radio galaxy zoo project will measure the relative populations of these hosts as a function of radio morphology and power while providing an avenue for the identification of rare and extreme radio structures. currently, we are investigating candidates for radio galaxies with extreme morphologies, such as giant radio galaxies, late-type host galaxies with extended radio emission and hybrid morphology radio sources. | radio galaxy zoo: host galaxies and radio morphologies derived from visual inspection |
using a single gravitational lens system observed at ≲ 5 mas resolution with very long baseline interferometry, we place a lower bound on the mass of the fuzzy dark matter (fdm) particle, ruling out mχ ≤ 4.4 × 10-21 ev with a 20:1 posterior odds ratio relative to a smooth lens model. we generalize our result to non-scalar and multiple-field models, such as vector fdm, with mχ,vec > 1.4 × 10-21 ev. due to the extended source structure and high angular resolution of the observation, our analysis is directly sensitive to the presence of granule structures in the main dark matter halo of the lens, which is the most generic prediction of fdm theories. a model based on well-understood physics of ultra-light dark matter fields in a gravitational potential well makes our result robust to a wide range of assumed dark matter fractions and velocity dispersions in the lens galaxy. our result is competitive with other lower bounds on mχ from past analyses, which rely on intermediate modelling of structure formation and/or baryonic effects. higher resolution observations taken at 10-100 ghz could improve our constraints by up to two orders of magnitude in the future. | a lensed radio jet at milli-arcsecond resolution - ii. constraints on fuzzy dark matter from an extended gravitational arc |
we present new alma band-7 data for a sample of six luminous quasars at z≃ 4.8, powered by fast-growing supermassive black holes (smbhs) with rather uniform properties: the typical accretion rates and black hole masses are l/{l}{edd}≃ 0.7 and {m}{bh}≃ {10}9 {m}⊙ . our sample consists of three “fir-bright” sources, which were individually detected in previous herschel/spire observations, with star formation rates of {sfr}> 1000 {m}⊙{{yr}}-1, and three “fir-faint” sources for which herschel stacking analysis implies a typical sfr of ∼400 {m}⊙{{yr}}-1. the dusty interstellar medium in the hosts of all six quasars is clearly detected in the alma data and resolved on scales of ∼2 kpc, in both continuum ({λ }{rest}∼ 150 μ {{m}}) and [{{c}} {{ii}}] λ 157.74 μ {{m}} line emission. the continuum emission is in good agreement with the expectations from the herschel data, confirming the intense sf activity in the quasar hosts. importantly, we detect companion sub-millimeter galaxies (smgs) for three sources—one fir-bright and two fir-faint, separated by ∼ 14{--}45 {kpc} and < 450 {km} {{{s}}}-1 from the quasar hosts. the [{{c}} {{ii}}]-based dynamical mass estimates for the interacting smgs are within a factor of ∼3 of the quasar hosts’ masses, while the continuum emission implies {{sfr}}{quasar}∼ (2{--}11)× {{sfr}}{smg}. our alma data therefore clearly support the idea that major mergers are important drivers for rapid early smbh growth. however, the fact that not all high-sfr quasar hosts are accompanied by interacting smgs and the gas kinematics as observed by alma suggest that other processes may be fueling these systems. our analysis thus demonstrates the diversity of host galaxy properties and gas accretion mechanisms associated with early and rapid smbh growth. | alma observations show major mergers among the host galaxies of fast-growing, high-redshift\u200b supermassive\u200b black holes |
cosmography is a powerful tool for investigating the universe kinematic and then for reconstructing the dynamics in a model-independent way. however, recent new measurements of supernovae ia and quasars have populated the hubble diagram up to high redshifts (z ∼ 7.5) and the application of the traditional cosmographic approach has become less straightforward due to the large redshifts implied. here we investigate this issue through an expansion of the luminosity distance-redshift relation in terms of orthogonal logarithmic polynomials. in particular, we point out the advantages of a new procedure called orthogonalization, and we show that such an expansion provides a very good fit in the whole z = 0 ÷ 7.5 range to both real and mock data obtained assuming various cosmological models. moreover, although the cosmographic series is tested well beyond its convergence radius, the parameters obtained expanding the luminosity distance-redshift relation for the lambda cold dark matter (λcdm) model are broadly consistent with the results from a fit of mock data obtained with the same cosmological model. this provides a method for testing the reliability of a cosmographic function to study cosmological models at high redshifts, and it demonstrates that the logarithmic polynomial series can be used to test the consistency of the λcdm model with the current hubble diagram of quasars and supernovae ia. we confirm a strong tension (at > 4σ) between the concordance cosmological model and the hubble diagram at z > 1.5. this tension is dominated by the contribution of quasars at z > 2 and also starts to be present in the few supernovae ia observed at z > 1. | cosmography by orthogonalized logarithmic polynomials |
the desi survey will measure large-scale structure using quasars as direct tracers of dark matter in the redshift range 0.9 < z < 2.1 and using quasar lyα forests at z > 2.1. we present two methods to select candidate quasars for desi based on imaging in three optical (g, r, z) and two infrared (w1, w2) bands. the first method uses traditional color cuts and the second utilizes a machine-learning algorithm. | preliminary target selection for the desi quasar (qso) sample |
the time delay measured between the images of gravitationally lensed quasars probes a combination of the angular diameter distance to the source-lens system and the mass density profile of the lens. observational campaigns to measure such systems have reported a determination of the hubble parameter h0 that shows significant tension with independent determination based on the cosmic microwave background (cmb) and large-scale structure (lss). we show that lens mass models that exhibit a cored component, coexisting with a cusp, probe a degenerate direction in the lens model parameter space, being an approximate mass sheet transformation. this family of lens models has not been considered by the cosmographic analyses. once added to the model, the cosmographic error budget should become dependent on stellar kinematics uncertainties. we propose that a core component coexisting with a cusp could bring the lensing measurements of h0 into accordance with the cmb/lss value. | could quasar lensing time delays hint to a core component in halos, instead of h0 tension? |
in this third paper of the series reporting on the reverberation mapping campaign of active galactic nuclei with asymmetric hβ emission-line profiles, we present results for 15 palomar-green quasars using spectra obtained between the end of 2016-2021 may. this campaign combines long time spans with relatively high cadence. for eight objects, both the time lags obtained from the entire light curves and the measurements from individual observing seasons are provided. reverberation mapping of nine of our targets has been attempted for the first time, while the results for six others can be compared with previous campaigns. we measure the hβ time lags over periods of years and estimate their black hole masses. the long duration of the campaign enables us to investigate their broad-line region (blr) geometry and kinematics for different years by using velocity-resolved lags, which demonstrate signatures of diverse blr geometry and kinematics. the blr geometry and kinematics of individual objects are discussed. in this sample, the blr kinematics of keplerian/virialized motion and inflow is more common than that of outflow. | monitoring agns with hβ asymmetry. iii. long-term reverberation mapping results of 15 palomar-green quasars |
the concept of the quasar main sequence is very attractive since it stresses correlations between various parameters and implies the underlying simplicity. in the optical plane defined by the width of the hβ line and the ratio of the equivalent width of the fe ii to hβ observed objects form a characteristic pattern. in this paper we use a physically motivated model to explain the distribution of quasars in the optical plane. continuum is modeled as an accretion disk with a hard x-ray power law uniquely tight to the disk at the basis of observational scaling, and the broad-line region distance is determined also from observational scaling. we perform the computations of the fe ii and hβ line production with the code cloudy. we have only six free parameters for an individual source, maximum temperature of accretion disk, eddington ratio, cloud density, cloud column density, microturbulence, and iron abundance, and only the last four remain as global parameters in our modeling of the whole sequence. our theoretically computed points cover well the optical plane part populated with the observed quasars, particularly if we allow for supersolar abundance of heavy elements. explanation of the exceptionally strong fe ii emitter requires stronger contribution from the dark sides of the clouds. analyzing the way our model covers the optical plane, we conclude that there is no single simple driver behind the sequence, as neither eddington ratio nor broadband spectrum shape plays the dominant role. also, the role of the viewing angle in providing the dispersion of the quasar main sequence is apparently not as strong as expected. | modeling of the quasar main sequence in the optical plane |
in this work, we include black hole (bh) seeding, growth, and feedback into our semi-analytic galaxy formation model, delphi. our model now fully tracks the accretion- and merger-driven hierarchical assembly of the dark matter halo, gas, stellar, and bh masses of high-redshift (z ≳ 5) galaxies. we explore a number of physical scenarios that include (i) two types of bh seeds (stellar and those from direct collapse bh); (ii) the impact of reionization; and (iii) the impact of instantaneous versus delayed galaxy mergers on the baryonic growth. using a minimal set of mass- and z-independent free parameters associated with star formation and bh growth, and their associated feedback, and including the suppressed bh growth in lower mass galaxies, we show that our model successfully reproduces all available data sets for early galaxies and quasars. while both reionization and delayed galaxy mergers have no sensible impact on the evolving ultraviolet luminosity function, the impact of the former dominates in determining the stellar mass density for observed galaxies as well as the bh mass function. we then use this model to predict the lisa detectability of merger events at high-z. as expected, mergers of stellar bhs dominate the merger rates for all scenarios and our model predicts an expected upper limit of about 20 mergers using instantaneous merging and no reionization feedback over the 4-yr mission duration. including the impact of delayed mergers and reionization feedback provides about 12 events over the same observational time-scale. | the hierarchical assembly of galaxies and black holes in the first billion years: predictions for the era of gravitational wave astronomy |
the mass and the spin of accreting and jetted black holes, at the center of active galactic nuclei (agns), can be probed by analyzing their electromagnetic spectra. for this purpose, we use the spin-modified fundamental plane of black hole activity, which non-linearly connects the following four variables (in the source frame): radio luminosity, x-ray or optical luminosity (via the [oiii] emission line), black hole mass and spin. taking into account the uncertainties in luminosity measurements, conversion factors, relativistic beaming and physical properties of the agn system, we derive lower bounds on the spins of a group of heavy, jetted agns. using these results, we study the direct implications on the mass spectrum of the ultra-light particles of scalar (axion-like), vector (dark photon) and tensor types (additional spin-2 particles). we close unexplored gap in the parameter space 10-20-10-19ev. we obtain upper bounds on the axion decay constant (equivalently lower bounds on the self-interaction strength) considering self-interactions could prevent the axion particles entering the instability, and be the reason for non-observation of superradiance. assuming axion is described by mass and decay constant, we obtain upper limits on what fraction of dark matter can be formed by ultra-light particles and find that single spieces axion-like light particle can constitute at most 10% of the dark matter in the mass range: 10-21 < μ (ev) < 10-17. | properties of ultralight bosons from heavy quasar spins via superradiance |
we present initial results from the cosmic origins spectrograph (cos) and gemini mapping the circumgalactic medium (cgmcgm ≡ cgm2) survey. the cgm2 survey consists of 1689 galaxies, all with high-quality gemini-gmos spectra, within 1 mpc of 22 z ≲ 1 quasars, all with a signal-to-noise ratio of ∼10 hubble space telescope/cos g130m+g160m spectra. for 572 of these galaxies with stellar masses 107 m⊙ < m⋆ < 1011 m⊙ and z ≲ 0.5, we show that the h i covering fraction above a threshold of nhi > 1014cm-2 is ≳0.5 within 1.5 virial radii (rvir ∼ r200m). we examine the h i kinematics and find that the majority of absorption lies within ±250 km s-1 of the galaxy systemic velocity. we examine h i covering fractions over a range of impact parameters to infer a characteristic size of the cgm, ${r}_{\mathrm{cgm}}^{14}$ , as a function of galaxy mass. ${r}_{\mathrm{cgm}}^{14}$ is the impact parameter at which the probability of observing an absorber with nhi >1014 cm-2 is >50%. in this framework, the radial extent of the cgm of m⋆ > 109.9 m⊙ galaxies is ${r}_{\mathrm{cgm}}^{14}={346}_{-53}^{+57}$ kpc or ${r}_{\mathrm{cgm}}^{14}\simeq 1.2{r}_{\mathrm{vir}}$ . intermediate-mass galaxies with 109.2 < m⋆/m⊙ < 109.9 have an extent of ${r}_{\mathrm{cgm}}^{14}={353}_{-50}^{+64}$ kpc or ${r}_{\mathrm{cgm}}^{14}\simeq 2.4{r}_{\mathrm{vir}}$ . low-mass galaxies, m⋆ < 109.2 m⊙, show a smaller physical scale of ${r}_{\mathrm{cgm}}^{14}={177}_{-65}^{+70}$ kpc and extend to ${r}_{\mathrm{cgm}}^{14}\simeq 1.6{r}_{\mathrm{vir}}$ . our analysis suggests that using rvir as a proxy for the characteristic radius of the cgm likely underestimates its extent. | cgm2 i: the extent of the circumgalactic medium traced by neutral hydrogen |
results from regular monitoring of relativistic compact binaries like psr 1913+16 are consistent with the dominant (quadrupole) order emission of gravitational waves (gws). we show that observations associated with the binary black hole (bbh) central engine of blazar oj 287 demand the inclusion of gravitational radiation reaction effects beyond the quadrupolar order. it turns out that even the effects of certain hereditary contributions to gw emission are required to predict impact flare timings of oj 287. we develop an approach that incorporates this effect into the bbh model for oj 287. this allows us to demonstrate an excellent agreement between the observed impact flare timings and those predicted from ten orbital cycles of the bbh central engine model. the deduced rate of orbital period decay is nine orders of magnitude higher than the observed rate in psr 1913+16, demonstrating again the relativistic nature of oj 287's central engine. finally, we argue that precise timing of the predicted 2019 impact flare should allow a test of the celebrated black hole “no-hair theorem” at the 10% level. | authenticating the presence of a relativistic massive black hole binary in oj 287 using its general relativity centenary flare: improved orbital parameters |
observations of high-redshift quasars provide information on the massive black holes (mbhs) powering them and the galaxies hosting them. current observations of z ≳ 6 hosts, at sub-millimetre wavelengths, trace the properties of cold gas, and these are used to compare with the correlations between mbhs and galaxies characterizing the z = 0 population. the relations at z = 0, however, rely on stellar-based tracers of the galaxy properties. we perform a very high resolution cosmological zoom-in simulation of a z = 7 quasar including state-of-the-art non-equilibrium chemistry, mbh formation, growth, and feedback, to assess the evolution of the galaxy host and the central mbh, and compare the results with recent alma observations of high-redshift quasars. we measure both the stellar-based quantities used to establish the z = 0 correlations, as well as the gas-based quantities available in z ≳ 6 observations, adopting the same assumptions and techniques used in observational studies. the high-redshift studies argued that mbhs at high redshift deviate from the local mbh-galaxy correlations. in our analysis of the single galaxy we evolve, we find that the high-redshift population sits on the same correlations as the local one, when using the same tracers used at z = 0. when using the gas-based tracers, however, mbhs appear to be overmassive. the discrepancy between local and high-redshift mbhs seems to be caused by the different tracers employed, and the necessary assumptions, and not by an intrinsic difference. better calibration of the tracers, higher resolution data, and availability of facilities that can probe the stellar population will be crucial to assess precisely and accurately high-redshift quasar hosts. | high-redshift quasars and their host galaxies - i. kinematical and dynamical properties and their tracers |
proximity zone fossils (pzfs) are ionization signatures around recently active galactic nuclei (agns) where metal species in the circumgalactic medium remain overionized after the agns have shut off due to their long recombination time scales. we explore cosmological zoom hydrodynamic simulations, using the eagle (evolution and assembly of galaxies and their environments) model paired with a non-equilibrium ionization and cooling module including time-variable agn radiation to model pzfs around star-forming disc galaxies in the z ~ 0.2 universe. previous simulations typically underestimated the ${o{\,}\small {\rm vi}}$ content of galactic haloes, but we show that plausible pzf models increase ${o{\,}\small {\rm vi}}$ column densities by 2 - 3 × to achieve the levels observed around cos-halos star-forming galaxies out to 150 kpc. models with agn bolometric luminosities ≳ 1043.6erg s- 1, duty cycle fractions ≲ 10 per cent, and agn lifetimes ≲ 106 yr are the most promising, because their supermassive black holes grow at the cosmologically expected rate and they mostly appear as inactive agn, consistent with cos-halos. the central requirement is that the typical star-forming galaxy hosted an active agn within a time-scale comparable to the recombination time of a high metal ion, which for circumgalactic ${o{\,}\small {\rm vi}}$ is ≈107 yr. ${{h{\,}\small {\rm i}}}$, by contrast, returns to equilibrium much more rapidly due to its low neutral fraction and does not show a significant pzf effect. ${o{\,}\small {\rm vi}}$ absorption features originating from pzfs appear narrow, indicating photoionization, and are often well aligned with lower metal ion species. pzfs are highly likely to affect the physical interpretation of circumgalactic high ionization metal lines if, as expected, normal galaxies host flickering agn. | flickering agn can explain the strong circumgalactic o vi observed by cos-halos |
the x-ray and mid-ir emission from active galactic nuclei (agns) are strongly correlated. however, while various published parameterizations of this correlation are consistent with the low-redshift, local seyfert galaxy population, extrapolations of these relations to high luminosity differ by an order of magnitude at ν {l}ν (6 μm) ∼ {10}47 {erg} {{{s}}}-1. using data from the wide-field infrared survey explorer, we determine the mid-ir luminosities of the most luminous quasars from the sloan digital sky survey and present a revised formulation of the x-ray to mid-ir relation of agns which is appropriate from the seyfert regime to the powerful quasar regime. | the x-ray to mid-infrared relation of agns at high luminosity |
supermassive black holes (bhs) reside in the centre of most local galaxies, but they also power active galactic nuclei and quasars, detected up to z = 7. these quasars put constraints on early bh growth and the mass of bh seeds. the scenario of `direct collapse' is appealing as it leads to the formation of large mass bh seeds, 104-106 m⊙, which eases explaining how quasars at z = 6-7 are powered by bhs with masses >109 m⊙. direct collapse, however, appears to be rare, as the conditions required by the scenario are that gas is metal-free, the presence of a strong photodissociating lyman-werner flux, and large inflows of gas at the centre of the halo, sustained for 10-100 myr. we performed several cosmological hydrodynamical simulations that cover a large range of box sizes and resolutions, thus allowing us to understand the impact of several physical processes on the distribution of direct collapse bhs. we identify haloes where direct collapse can happen, and derive the number density of bhs. we also investigate the discrepancies between hydrodynamical simulations, direct or post-processed, and semi-analytical studies. under optimistic assumptions, we find that for direct collapse to account for bhs in normal galaxies, the critical lyman-werner flux required for direct collapse must be about two orders of magnitude lower than predicted by 3d simulations that include detailed chemical models. however, when supernova feedback is relatively weak, enough direct collapse bhs to explain z = 6-7 quasars can be obtained for lyman-werner fluxes about one order of magnitude lower than found in 3d simulations. | on the number density of `direct collapse' black hole seeds |
we present a computationally efficient and fast semi-numerical technique for simulating the lyman α (ly α) absorption optical depth in presence of neutral hydrogen 'islands' left over from reionization at redshifts 5 ≲ z ≲ 6. the main inputs to the analysis are (i) a semi-numerical photon-conserving model of ionized regions during reionization (named script) along with a prescription for simulating the shadowing by neutral islands and (ii) the fluctuating gunn-peterson approximation to model the ly α absorption. our model is then used for simulating the large-scale fluctuations in the effective optical depth as observed along sightlines towards high-z quasars. our model is fully described by five parameters. by setting two of them to default values and varying the other three, we obtain the constraints on reionization history at 5 ≲ z ≲ 6 as allowed by the data. we confirm that reionization is not complete before z ∼ 5.6 at ≳2σ confidence, with the exact confidence limits depending on how the non-detections of the flux in the data are treated. we also confirm that the completion of reionization can be as late as z ∼ 5.2. with further improvements in the model and with more sightlines at z ∼ 6, we can take advantage of the computational efficiency of our analysis to obtain more stringent constraints on the ionization fraction at the tail end of reionization. | studying the lyman α optical depth fluctuations at z ∼ 5.5 using fast semi-numerical methods |
so far large and different data sets revealed the accelerated expansion rate of the universe, which is usually explained in terms of dark energy. the nature of dark energy is not yet known, and several models have been introduced: a non-zero cosmological constant, a potential energy of some scalar field, effects related to the non-homogeneous distribution of matter, or effects due to alternative theories of gravity. recently, a tension with the flat λcdm model has been discovered using a high-redshift hubble diagram of supernovae, quasars, and gamma-ray bursts (grb). here we use the union2 type ia supernovae and grb hubble diagram, and a set of direct measurements of the hubble parameter to explore different dark energy models. we use the chevallier-polarski-linder parametrization of the dark energy equation of state, a minimally coupled quintessence scalar field, and, finally, we consider models with dark energy at early times. we perform a statistical analysis based on the markov chain monte carlo method, and explore the probability distributions of the cosmological parameters for each of the competing models. we apply the akaike information criterion to compare these models: our analysis indicates that an evolving dark energy, described by a scalar field with exponential potential seems to be favoured by observational data. | prospects of high redshift constraints on dark energy models with the ep, i - eiso correlation in long gamma ray bursts |
we report the discovery, spectroscopic confirmation, and preliminary characterization of 24 gravitationally lensed quasars identified using gaia observations. candidates were selected in the pan-starrs footprint with quasar-like wise colours or as photometric quasars from sloan digital sky survey (sdss), requiring either multiple detections in gaia or a single gaia detection near a morphological galaxy. the pan-starrs grizy images were modelled for the most promising candidates and 60 candidate systems were followed up with the william herschel telescope. 13 of the lenses were discovered as gaia multiples and 10 as single gaia detections near galaxies. we also discover 1 lens identified through a quasar emission line in an sdss galaxy spectrum. the lenses have median image separation 2.13 arcsec and the source redshifts range from 1.06 to 3.36. 4 systems are quadruply imaged and 20 are doubly imaged. deep cfht data reveal an einstein ring in one double system. we also report 12 quasar pairs, 10 of which have components at the same redshift and require further follow-up to rule out the lensing hypothesis. we compare the properties of these lenses and other known lenses recovered by our search method to a complete sample of simulated lenses to show the lenses we are missing are mainly those with small separations and higher source redshifts. the initial gaia data release only catalogues all images of ∼30 per cent of known bright lensed quasars, however the improved completeness of gaia data release 2 will help find all bright lensed quasars on the sky. | gravitationally lensed quasars in gaia - ii. discovery of 24 lensed quasars |
in an effort to search for ly α emission from circum- and intergalactic gas on scales of hundreds of kpc around z ∼ 3 quasars, and thus characterize the physical properties of the gas in emission, we have initiated an extensive fast survey with the multi-unit spectroscopic explorer (muse): quasar snapshot observations with muse: search for extended ultraviolet emission (qso museum). in this work, we report the discovery of an enormous ly α nebula (elan) around the quasar sdss j102009.99+104002.7 at z = 3.164, which we followed-up with deeper muse observations. this elan spans ∼297 projected kpc, has an average ly α surface brightness sbly α ∼ 6.04 × 10-18 erg s-1 cm-2 arcsec-2(within the 2σ isophote) and is associated with an additional four previously unknown embedded sources: two ly α emitters and two faint active galactic nuclei (one type-1 and one type-2 quasar). by mapping at high significance, the line-of-sight velocity in the entirety of the observed structure, we unveiled a large-scale coherent rotation-like pattern spanning ∼300 km s-1 with a velocity dispersion of <270 km s-1, which we interpret as a signature of the inspiraling accretion of substructures within the quasar's host halo. future multiwavelength data will complement our muse observations and are definitely needed to fully characterize such a complex system. none the less, our observations reveal the potential of new sensitive integral-field spectrographs to characterize the dynamical state of diffuse gas on large scales in the young universe, and thereby witness the assembly of galaxies. | inspiraling halo accretion mapped in ly α emission around a z ∼ 3 quasar |
stars can either be formed in or captured by the accretion disks in active galactic nuclei (agns). these agn stars are irradiated and subject to extreme levels of accretion, which can turn even low-mass stars into very massive ones (m > 100m⊙) whose evolution may result in the formation of massive compact objects (m > 10m⊙). here we explore the spins of these agn stars and the remnants they leave behind. we find that agn stars rapidly spin up via accretion, eventually reaching near-critical rotation rates. they further maintain near-critical rotation even as they shed their envelopes, become compact, and undergo late stages of burning. this makes them good candidates to produce high-spin massive black holes, such as the ones seen by ligo-virgo in gw 190521g, as well as long gamma-ray bursts and the associated chemical pollution of the agn disk. | stellar evolution in the disks of active galactic nuclei produces rapidly rotating massive stars |
galaxy mergers occur frequently in the early universe1 and bring multiple supermassive black holes (smbhs) into the nucleus, where they may eventually coalesce. identifying post-merger-scale (that is, less than around a few kpc) dual smbhs is a critical pathway to understanding their dynamical evolution and successive mergers2. whereas serendipitous discovery of ~kpc-scale dual smbhs at z < 1 is possible3, such systems are elusive at z > 2 but critical in constraining the progenitors of smbh mergers. the redshift z ≈ 2 also marks the epoch of peak activity of luminous quasars4, and therefore the probing of this spatial regime at high redshift is of particular importance in understanding the evolution of quasars. however, given stringent resolution requirements, there is currently no confirmed <10 kpc physical smbh pair at z > 2 (refs. 5-8). here, we report two sub-arcsec double quasars at z > 2 that were discovered from a targeted search with a novel astrometric technique, demonstrating a high success rate (≳50%) in this systematic approach. these high-redshift double quasars could be the long-sought kpc-scale dual smbhs, or sub-arcsec gravitationally lensed quasar images. one of these double quasars (at z = 2.95) was spatially resolved with optical spectroscopy, and slightly favours the scenario of a physical quasar pair with a projected separation of 3.5 kpc (0.46″). follow-up observations of double quasars discovered by this targeted approach will be able to provide observational constraints on kpc-scale dual smbhs at z > 2. | a hidden population of high-redshift double quasars unveiled by astrometry |
we present the first results of a project called sagan, which is dedicated solely to the studies of relatively rare megaparsec-scale radio galaxies in the universe, called giant radio galaxies (grgs). we have identified 162 new grgs primarily from the nrao vla sky survey with sizes ranging from ∼0.71 mpc to ∼2.82 mpc in the redshift range of ∼0.03-0.95, of which 23 are hosted by quasars (giant radio quasars). as part of the project sagan, we have created a database of all known grgs, the grg catalogue, from the literature (including our new sample); it includes 820 sources. for the first time, we present the multi-wavelength properties of the largest sample of grgs. this provides new insights into their nature. our results establish that the distributions of the radio spectral index and the black hole mass of grgs do not differ from the corresponding distributions of normal-sized radio galaxies (rgs). however, grgs have a lower eddington ratio than rgs. using the mid-infrared data, we classified grgs in terms of their accretion mode: either a high-power radiatively efficient high-excitation state, or a radiatively inefficient low-excitation state. this enabled us to compare key physical properties of their active galactic nuclei, such as the black hole mass, spin, eddington ratio, jet kinetic power, total radio power, magnetic field, and size. we find that grgs in high-excitation state statistically have larger sizes, stronger radio power, jet kinetic power, and higher eddington ratio than those in low-excitation state. our analysis reveals a strong correlation between the black hole eddington ratio and the scaled jet kinetic power, which suggests a disc-jet coupling. our environmental study reveals that ∼10% of all grgs may reside at the centres of galaxy clusters, in a denser galactic environment, while the majority appears to reside in a sparse environment. the probability of finding the brightest cluster galaxy as a grg is quite low and even lower for high-mass clusters. we present new results for grgs that range from black hole mass to large-scale environment properties. we discuss their formation and growth scenarios, highlighting the key physical factors that cause them to reach their gigantic size. tables a1-a4 are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/642/a153 | search and analysis of giant radio galaxies with associated nuclei (sagan). i. new sample and multi-wavelength studies |
the far-infrared fine-structure line [c ii] at 1900.5 ghz is known to be one of the brightest cooling lines in local galaxies, and therefore it has been suggested to be an efficient tracer for star formation in very high redshift galaxies. however, recent results for galaxies at z > 6 have yielded numerous non-detections in star-forming galaxies, except for quasars and submillimetre galaxies. we report the results of alma observations of two lensed, star-forming galaxies at z = 6.029 and z = 6.703. the galaxy a383-5.1 (star formation rate [sfr] of 3.2 m⊙ yr-1 and magnification of μ = 11.4 ± 1.9) shows a line detection with l_[c ii] = 8.9× 106 l⊙, making it the lowest l_[c ii] detection at z > 6. for ms0451-h (sfr = 0.4 m⊙ yr-1 and μ = 100 ± 20) we provide an upper limit of l_[c ii] < 3× 105 l⊙, which is 1 dex below the local sfr-l_[c ii] relations. the results are consistent with predictions for low-metallicity galaxies at z > 6; however, other effects could also play a role in terms of decreasing l[cii]. the detection of a383-5.1 is encouraging and suggests that detections are possible, but much fainter than initially predicted. | [c ii] emission in z ∼ 6 strongly lensed, star-forming galaxies |
ly α emission lines are typically found to be redshifted with respect to the systemic redshifts of galaxies, likely due to resonant scattering of ly α photons. here, we measure the average velocity offset for a sample of 96 z ≈ 3.3 ly α emitters (laes) with a median ly α flux (luminosity) of ≈10<>sup>-17 erg cm-2 s-1 (≈1042 erg s-1) and a median star formation rate (sfr) of ≈1.3 m⊙ yr-1 (not corrected for possible dust extinction), detected by the multi-unit spectroscopic explorer as part of our musequbes circumgalactic medium (cgm) survey. by postulating that the stacked cgm absorption profiles of these laes, probed by eight background quasars, must be centred on the systemic redshift, we measure an average velocity offset, voffset = 171\pm 8 km s-1, between the ly α emission peak and the systemic redshift. the observed voffset is lower by factors of ≈1.4 and ≈2.6 compared to the velocity offsets measured for narrow-band-selected laes and lyman break galaxies, respectively, which probe galaxies with higher masses and sfrs. consistent with earlier studies based on direct measurements for individual objects, we find that the voffset is correlated with the full width at half-maximum of the red peak of the ly α line, and anticorrelated with the rest-frame equivalent width. moreover, we find that voffset is correlated with sfr with a sub-linear scaling relation, voffset ∝ sft0.16±0.03. adopting the mass scaling for main-sequence galaxies, such a relation suggests that voffset scales with the circular velocity of the dark matter haloes hosting the laes. | musequbes: calibrating the redshifts of ly α emitters using stacked circumgalactic medium absorption profiles |
starting from a summary of detection statistics of our recent x-shooter campaign, we review the major surveys, both space and ground based, for emission counterparts of high-redshift damped ly α absorbers (dlas) carried out since the first detection 25 yr ago. we show that the detection rates of all surveys are precisely reproduced by a simple model in which the metallicity and luminosity of the galaxy associated to the dla follow a relation of the form, muv = -5 × ([m/h] + 0.3) - 20.8, and the dla cross-section follows a relation of the form σ _{dla} ∝ l^{0.8}. specifically, our spectroscopic campaign consists of 11 dlas pre-selected based on their equivalent width of si ii λ1526 to have a metallicity higher than [si/h] > -1. the targets have been observed with the x-shooter spectrograph at the very large telescope to search for emission lines around the quasars. we observe a high detection rate of 64 per cent (7/11), significantly higher than the typical ∼10 per cent for random, h i-selected dla samples. we use the aforementioned model, to simulate the results of our survey together with a range of previous surveys: spectral stacking, direct imaging (using the 'double dla' technique), long-slit spectroscopy, and integral field spectroscopy. based on our model results, we are able to reconcile all results. some tension is observed between model and data when looking at predictions of ly α emission for individual targets. however, the object-to-object variations are most likely a result of the significant scatter in the underlying scaling relations as well as uncertainties in the amount of dust which affects the emission. | consensus report on 25 yr of searches for damped ly α galaxies in emission: confirming their metallicity-luminosity relation at z ≳ 2 |
the observed scatter in intergalactic lyα opacity at z ≲ 6 requires large-scale fluctuations in the neutral fraction of the intergalactic medium (igm) after the expected end of reionization. post-reionization models that explain this scatter invoke fluctuations in either the ionizing ultraviolet background (uvb) or igm temperature. these models make very different predictions, however, for the relationship between lyα opacity and local density. here, we test these models using lyα-emitting galaxies (laes) to trace the density field surrounding the longest and most opaque known lyα trough at z < 6. using deep subaru hyper suprime-cam narrowband imaging, we find a highly significant deficit of z ≃ 5.7 laes within 20 {{{h}}}-1 {mpc} of the trough. the results are consistent with a model in which the scatter in lyα opacity near z ∼ 6 is driven by large-scale uvb fluctuations, and disfavor a scenario in which the scatter is primarily driven by variations in igm temperature. uvb fluctuations at this epoch present a boundary condition for reionization models, and may help shed light on the nature of the ionizing sources. | evidence for large-scale fluctuations in the metagalactic ionizing background near redshift six |
we present 0.″035 resolution (~200 pc) imaging of the 158 μm [c ii] line and the underlying dust continuum of the z = 6.9 quasar j234833.34-305410.0. the 18 hour atacama large millimeter/submillimeter array observations reveal extremely compact emission (diameter ~1 kpc) that is consistent with a simple, almost face-on, rotation-supported disk with a significant velocity dispersion of ~160 km s-1. the gas mass in just the central 200 pc is ~4 × 109 m ⊙, about a factor of two higher than that of the central supermassive black hole. consequently we do not resolve the black hole's sphere of influence, and find no kinematic signature of the central supermassive black hole. kinematic modeling of the [c ii] line shows that the dynamical mass at large radii is consistent with the gas mass, leaving little room for a significant mass contribution by stars and/or dark matter. the toomre-q parameter is less than unity throughout the disk, and thus is conducive to star formation, consistent with the high-infrared luminosity of the system. the dust in the central region is optically thick, at a temperature >132 k. using standard scaling relations of dust heating by star formation, this implies an unprecedented high star formation rate density of >104 m ⊙ yr-1 kpc-2. such a high number can still be explained with the eddington limit for star formation under certain assumptions, but could also imply that the central supermassive black hole contributes to the heating of the dust in the central 200 pc. | alma 200 pc imaging of a z 7 quasar reveals a compact, disk-like host galaxy |
using six years of spectroscopic monitoring of the luminous quasar he 0435-4312 (z = 1.2231) with the southern african large telescope, in combination with photometric data (catalina, ogle, salticam, and bmt), we determined a rest-frame time delay of ${296}_{-14}^{+13}$ days between the mg ii broad-line emission and the ionizing continuum using seven different time-delay inference methods. time-delay artifact peaks and aliases were mitigated using the bootstrap method and prior weighting probability function, as well as by analyzing unevenly sampled mock light curves. the mg ii emission is considerably variable with a fractional variability of ∼5.4%, which is comparable to the continuum variability (∼4.8%). because of its high luminosity (l3000 = 1046.4 erg s-1), the source is beneficial for a further reduction of the scatter along the mg ii-based radius-luminosity relation and its extended versions, especially when the highly accreting subsample that has an rms scatter of ∼0.2 dex is considered. this opens up the possibility of using the high-accretor mg ii-based radius-luminosity relation for constraining cosmological parameters. with the current sample of 27 reverberation-mapped sources, the best-fit cosmological parameters (ωm, ωλ) = (0.19; 0.62) are consistent with the standard cosmological model within the 1σ confidence level. | time delay of mg ii emission response for the luminous quasar he 0435-4312: toward application of the high-accretor radius-luminosity relation in cosmology |
we present trinity, a flexible empirical model that self-consistently infers the statistical connection between dark matter haloes, galaxies, and supermassive black holes (smbhs). trinity is constrained by galaxy observables from 0 < z < 10 [galaxies' stellar mass functions, specific and cosmic star formation rates (sfrs), quenched fractions, and uv luminosity functions] and smbh observables from 0 < z < 6.5 (quasar luminosity functions, quasar probability distribution functions, active black hole mass functions, local smbh mass-bulge mass relations, and the observed smbh mass distributions of high-redshift bright quasars). the model includes full treatment of observational systematics [e.g. active galactic nucleus (agn) obscuration and errors in stellar masses]. from these data, trinity infers the average smbh mass, smbh accretion rate, merger rate, and eddington ratio distribution as functions of halo mass, galaxy stellar mass, and redshift. key findings include: (1) the normalization and the slope of the smbh mass-bulge mass relation increases mildly from z = 0 to z = 10; (2) the best-fitting agn radiative+kinetic efficiency is ~0.05-0.06, but can be in the range ~0.035-0.07 with alternative input assumptions; (3) agns show downsizing, i.e. the eddington ratios of more massive smbhs start to decrease earlier than those of lower mass objects; (4) the average ratio between average smbh accretion rate and sfr is ~10-3 for low-mass galaxies, which are primarily star-forming. this ratio increases to ~10-1 for the most massive haloes below z ~ 1, where star formation is quenched but smbhs continue to accrete. | trinity i: self-consistently modelling the dark matter halo-galaxy-supermassive black hole connection from z = 0-10 |
we present cosmological results inferred from the effective-field theory (eft) analysis of the full-shape of eboss quasars (qso) power spectrum. we validate our analysis pipeline against simulations, and find overall good agreement between the analyses in fourier and configuration space. keeping the baryon abundance and the spectral tilt fixed, we reconstruct at 68% cl the fractional matter abundance ω m , the reduced hubble constant h, and the clustering amplitude σ 8, to respectively ω m= 0.327 ± 0.035, h = 0.655 ± 0.034, and σ 8 = 0.880 ± 0.083 from eboss qso alone. these constraints are consistent at ≲ 1.8σ with the ones from planck and from the eft analysis of boss full-shape. interestingly s 8 reconstructed from eboss qso is slightly higher than that deduced from planck and boss, although statistically consistent. in combination with the eft likelihood of boss, supernovae from pantheon, and bao from lyman-α and 6df/mgs, constraints improve to ω m= 0.2985 ± 0.0069 and h = 0.6803 ± 0.0075, in agreement with planck and with similar precision. we also explore one-parameter extensions to λcdm and find that results are consistent with flat λcdm at ≲ 1.3σ. we obtain competitive constraints on the curvature density fraction ω k= -0.039 ± 0.029, the dark energy equation of state w 0 = -1.038 ± 0.041, the effective number of relativistic species n eff = 3.44+0.44 -0.91 at 68% cl, and the sum of neutrino masses ∑ mν < 0.274 ev at 95% cl, without planck data. including planck data, contraints significantly improve thanks to the large lever arm in redshift between lss and cmb measurements. in particular, we obtain the stringent constraint ∑ mν < 0.093 ev, competitive with recent lyman-α forest power spectrum bound. | cosmological inference from the eftoflss: the eboss qso full-shape analysis |
we report new northern extended millimeter array observations of the [c ii]158 μm, [n ii]205 μm, and [o i]146 μm atomic fine structure lines (fsls) and dust continuum emission of j1148+5251, a z = 6.42 quasar, which probe the physical properties of its interstellar medium (ism). the radially averaged [c ii]158 μm and dust continuum emission have similar extensions (up to $\theta ={2.51}_{-0.25}^{+0.46}\ \mathrm{arcsec}$ , corresponding to $r={9.8}_{-2.1}^{+3.3}\ \mathrm{kpc}$ , accounting for beam convolution), confirming that j1148+5251 is the quasar with the largest [c ii]158 μm-emitting reservoir known at these epochs. moreover, if the [c ii]158 μm emission is examined only along its ne-sw axis, a significant excess (>5.8σ) of [c ii]158 μm emission (with respect to the dust) is detected. the new wide-bandwidth observations enable us to accurately constrain the continuum emission, and do not statistically require the presence of broad [c ii]158 μm line wings that were reported in previous studies. we also report the first detection of the [o i]146 μm and (tentatively) [n ii]205 μm emission lines in j1148+5251. using fsl ratios of the [c ii]158 μm, [n ii]205 μm, [o i]146 μm, and previously measured [c i]369 μm emission lines, we show that j1148+5251 has similar ism conditions compared to lower-redshift (ultra)luminous infrared galaxies. cloudy modeling of the fsl ratios excludes x-ray-dominated regions and favors photodissociation regions as the origin of the fsl emission. we find that a high radiation field (103.5-4.5 g 0), a high gas density (n ≃ 103.5-4.5 cm-3), and an h i column density of 1023 cm-2 reproduce the observed fsl ratios well. | physical constraints on the extended interstellar medium of the z = 6.42 quasar j1148+5251: [c ii]158 μm, [n ii]205 μm, and [o i]146 μm observations |
the growth of the most massive black holes in the early universe, consistent with the detection of highly luminous quasars at z > 6 implies sustained, critical accretion of material to grow and power them. given a black hole (bh) seed scenario, it is still uncertain which conditions in the early universe allow the fastest bh growth. large-scale hydrodynamical cosmological simulations of structure formation allow us to explore the conditions conducive to the growth of the earliest supermassive bhs. we use the cosmological hydrodynamic simulation bluetides, which incorporates a variety of baryon physics in a (400 h-1mpc)3 volume with 0.7 trillion particles to follow the earliest phases of bh critical growth. at z = 8 the most massive bhs (a handful) approach masses of 108 m_{⊙} with the most massive (with m_bh = 4 × 10^8 m_{⊙}) being found in an extremely compact (compared to present day) spheroid-dominated host galaxy. examining the large-scale environment of hosts, we find that the initial tidal field is more important than overdensity in setting the conditions for early bh growth. in regions of low tidal fields gas accretes 'cold' on to the bh and falls along thin, radial filaments straight into the centre forming the most compact galaxies and most massive bhs at the earliest times. regions of high tidal fields instead induce larger coherent angular momenta and influence the formation of the first population of massive compact discs. the extreme early growth depends on the early interplay of high gas densities and the tidal field that shapes the mode of accretion. mergers may play a minor role in the formation of the first generation, rare massive bhs. | the origin of the most massive black holes at high-z: bluetides and the next quasar frontier |
we decompose the lyman-α (lyα) forest of an extensive sample of 75 high signal-to-noise ratio and high-resolution quasar spectra into a collection of voigt profiles. absorbers located near caustics in the peculiar velocity field have the smallest doppler parameters, resulting in a low-b cutoff in the b-{n}{{h}{{i}}} distribution set primarily by the thermal state of the intergalactic medium (igm). we fit this cutoff as a function of redshift over the range 2.0≤slant z≤slant 3.4, which allows us to measure the evolution of the igm temperature-density (t={t}0{(ρ /{ρ }0)}γ -1) relation parameters t 0 and γ. we calibrate our measurements against mock lyα forest data generated using 26 hydrodynamic simulations with different thermal histories from the thermal suite, also encompassing different values of the igm pressure smoothing scale. we adopt a forward-modeling approach and self-consistently apply the same algorithms to both data and simulations, propagating both statistical and modeling uncertainties via monte carlo. the redshift evolution of t 0 (γ) shows a suggestive peak (dip) at z = 2.9 (z = 3). our measured evolution of t 0 and γ is generally in good agreement with previous determinations in the literature. both the peak in the evolution of t 0 at z = 2.8, as well as the high temperatures {t}0≃ {{15,000}}{--}{{20,000}} {{k}} that we observe at 2.4 < z < 3.4, strongly suggest that a significant episode of heating occurred after the end of h i reionization, which was most likely the cosmic reionization of he ii. | a new measurement of the temperature-density relation of the igm from voigt profile fitting |
the interstellar medium is crucial to understanding the physics of active galaxies and the coevolution between supermassive black holes and their host galaxies. however, direct gas measurements are limited by sensitivity and other uncertainties. dust provides an efficient indirect probe of the total gas. we apply this technique to a large sample of quasars, whose total gas content would be prohibitively expensive to measure. we present a comprehensive study of the full (1 to 500 μm) infrared spectral energy distributions of 87 redshift <0.5 quasars selected from the palomar-green sample, using photometric measurements from 2mass, wise, and herschel, combined with spitzer mid-infrared (5-40 μm) spectra. with a newly developed bayesian markov chain monte carlo fitting method, we decompose various overlapping contributions to the integrated spectral energy distribution, including starlight, warm dust from the torus, and cooler dust on galaxy scales. this procedure yields a robust dust mass, which we use to infer the gas mass, using a gas-to-dust ratio constrained by the host galaxy stellar mass. most (90%) quasar hosts have gas fractions similar to those of massive, star-forming galaxies, although a minority (10%) seem genuinely gas-deficient, resembling present-day massive early-type galaxies. this result indicates that “quasar mode” feedback does not occur or is ineffective in the host galaxies of low-redshift quasars. we also find that quasars can boost the interstellar radiation field and heat dust on galactic scales. this cautions against the common practice of using the far-infrared luminosity to estimate the host galaxy star formation rate. | on the gas content and efficiency of agn feedback in low-redshift quasars |
we investigate the contribution of reprocessed continuum emission (1000-10 000 å) originating in broad-line region (blr) gas, the diffuse continuum (dc), to the wavelength-dependent continuum delays measured in agn disc reverberation mapping experiments. assuming a spherical blr geometry, we adopt a local optimally emitting cloud (loc) model for the blr that approximately reproduces the broad emission-line strengths of the strongest uv lines (ly α and c iv) in ngc 5548. within this loc framework, we explore how assumptions about the gas hydrogen density and column density distributions influence flux and delay spectra of the dc. we find that: (i) models which match well measured emission-line luminosities and time delays also produce a significant dc component, (ii) increased n_h and/or n_h, particularly at smaller blr radii, result in larger dc luminosities and reduced dc delays, (iii) in a given continuum band the relative importance of the dc component to the measured interband delays is proportional (though not 1:1) to its fractional contribution to the total light in that band, (iv) the measured dc delays and dc variability amplitude depend also on the variability amplitude and characteristic variability time-scale of the driving continuum, (v) the dc radial surface emissivity distributions f(r) approximate power laws in radius with indices close to -2 (≈1:1 response to variations in the driving continuum flux), thus their physics is relatively simple and less sensitive to the unknown geometry and uncertainties in radiative transfer. finally, we provide a simple recipe for estimating the dc contribution in disc reverberation mapping experiments. | quantifying the impact of variable blr diffuse continuum contributions on measured continuum interband delays |
numerical simulations of cosmological structure formation show that the universe’s most massive clusters, and the galaxies living in those clusters, assemble rapidly at early times (2.5\lt z\lt 4). while more than 20 proto-clusters have been observed at z≳ 2 based on associations of 5-40 galaxies around rare sources, the observational evidence for rapid cluster formation is weak. here we report observations of an asymmetric filamentary structure at z = 2.47 containing 7 starbursting, submillimeter-luminous galaxies and 5 additional active galactic nuclei (agns) within a comoving volume of 15,000 mpc3. as the expected lifetime of both the luminous agn and starburst phase of a galaxy is ∼100 myr, we conclude that these sources were likely triggered in rapid succession by environmental factors or, alternatively, the duration of these cosmologically rare phenomena is much longer than prior direct measurements suggest. the stellar mass already built up in the structure is ∼1012 {m}⊙and we estimate that the cluster mass will exceed that of the coma supercluster at z∼ 0. the filamentary structure is in line with hierarchical growth simulations that predict that the peak of cluster activity occurs rapidly at z\gt 2. | a massive, distant proto-cluster at z = 2.47 caught in a phase of rapid formation? |
approximately 200 supermassive black holes (smbhs) have been discovered within the first ∼gigayear after the big bang. one pathway for the formation of smbhs is through the collapse of supermassive stars (smss). a possible obstacle to this scenario is that the collapsing gas fragments and forms a cluster of main-sequence stars. here, we raise the possibility that stellar collisions may be sufficiently frequent and energetic to inhibit the contraction of the massive protostar, avoiding strong uv radiation driven outflows, and allowing it to continue growing into an sms. we investigate this scenario with semianalytic models incorporating star formation; gas accretion; dynamical friction from stars and gas; stellar collisions; and gas ejection. we find that when the collapsing gas fragments at a density of ≲3 × 1010 cm-3, the central protostar contracts due to infrequent stellar mergers, and in turn photoevaporates the remaining collapsing gas, resulting in the formation of a ≲104 m⊙ object. on the other hand, when the collapsing gas fragments at higher densities (expected for a metal-poor cloud with z ≲ 10-5 z⊙ with suppressed h2 abundance) the central protostar avoids contraction and keeps growing via frequent stellar mergers, reaching masses as high as ∼105-106 m⊙. we conclude that frequent stellar mergers represent a possible pathway to form massive bhs in the early universe. | making a supermassive star by stellar bombardment |
we explore the circumgalactic metal content traced by commonly observed low ion absorbers, including c ii, si ii, si iii, si iv, and mg ii. we use a set of cosmological hydrodynamical zoom simulations run with the eagle model and including a non-equilibrium ionization and cooling module that follows 136 ions. the simulations of z ≈ 0.2 l* (m200 = 1011.7 - 1012.3m⊙) haloes hosting star-forming galaxies and group-sized (m200 = 1012.7 - 1013.3m⊙) haloes hosting mainly passive galaxies reproduce key trends observed by the cos-halos survey - low ion column densities show 1) little dependence on galaxy-specific star formation rate, 2) a patchy covering fraction indicative of 104 k clumps with a small volume filling factor, and 3) a declining covering fraction as impact parameter increases from 20-160kpc. simulated si ii, si iii, si iv, c ii, and c iii column densities show good (mostly within 0.3 dex) agreement with observations, while mg ii is under-predicted. low ions trace a significant metal reservoir, ≈108m⊙, residing primarily at 10-100kpc from star-forming and passive central galaxies. these clumps preferentially flow inwards and most will accrete onto the central galaxy within the next several gyr, while a small fraction are entrained in strong outflows. a multiphase structure describes the inner cgm (<0.5r200) with low-ion metal clumps surrounded by a hot, ambient medium. the dense, cool phase is separate from the o vi observed by cos-halos, which arises from the outer cgm (>0.5r200) tracing virial temperature gas around l* galaxies. our simulations support previous ionization models indicating that cloud covering factors decline while densities and pressures show little decline with increasing impact parameter (typically <0.3 dex from 40 to 160 kpc). we find the cool clumps have lower pressures than the ambient medium they are embedded in, and discuss that numerical effects within the hydrodynamic solver likely play a role. | the multiphase circumgalactic medium traced by low metal ions in eagle zoom simulations |
we present the first self-consistent prediction for the distribution of formation time-scales for close supermassive black hole (smbh) pairs following galaxy mergers. using romulus25, the first large-scale cosmological simulation to accurately track the orbital evolution of smbhs within their host galaxies down to sub-kpc scales, we predict an average formation rate density of close smbh pairs of 0.013 cmpc-3 gyr-1. we find that it is relatively rare for galaxy mergers to result in the formation of close smbh pairs with sub-kpc separation and those that do form are often the result of gyr of orbital evolution following the galaxy merger. the likelihood and time-scale to form a close smbh pair depends strongly on the mass ratio of the merging galaxies, as well as the presence of dense stellar cores. low stellar mass ratio mergers with galaxies that lack a dense stellar core are more likely to become tidally disrupted and deposit their smbh at large radii without any stellar core to aid in their orbital decay, resulting in a population of long-lived `wandering' smbhs. conversely, smbhs in galaxies that remain embedded within a stellar core form close pairs in much shorter time-scales on average. this time-scale is a crucial, though often ignored or very simplified, ingredient to models predicting smbh mergers rates and the connection between smbh and star formation activity. | dancing to changa: a self-consistent prediction for close smbh pair formation time-scales following galaxy mergers |
we study the molecular gas properties of high-z galaxies observed in the alma spectroscopic survey (aspecs) that targets an ∼1 arcmin2 region in the hubble ultra deep field (udf), a blind survey of co emission (tracing molecular gas) in the 3 and 1 mm bands. of a total of 1302 galaxies in the field, 56 have spectroscopic redshifts and correspondingly well-defined physical properties. among these, 11 have infrared luminosities {l}{ir}\gt {10}11 {l}⊙ , i.e., a detection in co emission was expected. out of these, 7 are detected at various significance in co, and 4 are undetected in co emission. in the co-detected sources, we find co excitation conditions that are lower than those typically found in starburst/sub-mm galaxy/qso environments. we use the co luminosities (including limits for non-detections) to derive molecular gas masses. we discuss our findings in the context of previous molecular gas observations at high redshift (star formation law, gas depletion times, gas fractions): the co-detected galaxies in the udf tend to reside on the low-{l}{ir} envelope of the scatter in the {l}{ir}{--}{l}{co}\primerelation, but exceptions exist. for the co-detected sources, we find an average depletion time of ∼1 gyr, with significant scatter. the average molecular-to-stellar mass ratio ({m}{{h}2}/m *) is consistent with earlier measurements of main-sequence galaxies at these redshifts, and again shows large variations among sources. in some cases, we also measure dust continuum emission. on average, the dust-based estimates of the molecular gas are a factor ∼2-5× smaller than those based on co. when we account for detections as well as non-detections, we find large diversity in the molecular gas properties of the high-redshift galaxies covered by aspecs. | the alma spectroscopic survey in the hubble ultra deep field: molecular gas reservoirs in high-redshift galaxies |
we imaged, with alma and argos/luci, the molecular gas and dust and stellar continuum in xid2028, which is an obscured quasi-stellar object (qso) at z = 1.593, where the presence of a massive outflow in the ionised gas component traced by the [oiii]5007 emission has been resolved up to 10 kpc. this target represents a unique test case to study qso feedback in action at the peak epoch of agn-galaxy co-evolution. the qso was detected in the co(5 - 4) transition and in the 1.3 mm continuum at 30 and 20σ significance, respectively; both emissions are confined in the central (<2 kpc) radius area. our analysis suggests the presence of a fast rotating molecular disc (v 400 km s-1) on very compact scales well inside the galaxy extent seen in the rest-frame optical light ( 10 kpc, as inferred from the luci data). adding available measurements in additional two co transitions, co(2 - 1) and co(3 - 2), we could derive a total gas mass of 1010 m⊙, thanks to a critical assessment of co excitation and the comparison with the rayleigh-jeans continuum estimate. this translates into a very low gas fraction (<5%) and depletion timescales of 40-75 myr, reinforcing the result of atypical gas consumption conditions in xid2028, possibly because of feedback effects on the host galaxy. finally, we also detect the presence of high velocity co gas at 5σ, which we interpret as a signature of galaxy-scale molecular outflow that is spatially coincident with the ionised gas outflow. xid2028 therefore represents a unique case in which the measurement of total outflowing mass, of 500-800 m⊙ yr-1 including the molecular and atomic components in both the ionised and neutral phases, was attempted for a high-z qso. | molecular outflow and feedback in the obscured quasar xid2028 revealed by alma |
ngc 1266 is a nearby lenticular galaxy that harbors a massive outflow of molecular gas powered by the mechanical energy of an active galactic nucleus (agn). it has been speculated that such outflows hinder star formation (sf) in their host galaxies, providing a form of feedback to the process of galaxy formation. previous studies, however, indicated that only jets from extremely rare, high-power quasars or radio galaxies could impart significant feedback on their hosts. here we present detailed observations of the gas and dust continuum of ngc 1266 at millimeter wavelengths. our observations show that molecular gas is being driven out of the nuclear region at \dot{m}_out ≈ 110 m_⊙ yr-1, of which the vast majority cannot escape the nucleus. only 2 m ⊙ yr-1 is actually capable of escaping the galaxy. most of the molecular gas that remains is very inefficient at forming stars. the far-infrared emission is dominated by an ultra-compact (lsim 50 pc) source that could either be powered by an agn or by an ultra-compact starburst. the ratio of the sf surface density (σsfr) to the gas surface density (σ _h_2) indicates that sf is suppressed by a factor of ≈50 compared to normal star-forming galaxies if all gas is forming stars, and ≈150 for the outskirt (98%) dense molecular gas if the central region is powered by an ultra-compact starburst. the agn-driven bulk outflow could account for this extreme suppression by hindering the fragmentation and gravitational collapse necessary to form stars through a process of turbulent injection. this result suggests that even relatively common, low-power agns are able to alter the evolution of their host galaxies as their black holes grow onto the m-σ relation. | suppression of star formation in ngc 1266 |
our understanding of the unification of jetted agn has evolved greatly as jet samples have increased in size. here, based on the largest-ever sample of over 2000 well-sampled jet spectral energy distributions, we examine the synchrotron peak frequency - peak luminosity plane, and find little evidence for the anticorrelation known as the blazar sequence. instead, we find strong evidence for a dichotomy in jets, between those associated with efficient or 'quasar-mode' accretion (strong/type ii jets) and those associated with inefficient accretion (weak/type i jets). type ii jets include those hosted by high-excitation radio galaxies, flat-spectrum radio quasars (fsrq), and most low-frequency-peaked bl lac objects. type i jets include those hosted by low-excitation radio galaxies and blazars with synchrotron peak frequency above 1015 hz (nearly all bl lac objects). we have derived estimates of the total jet power for over 1000 of our sources from low-frequency radio observations, and find that the jet dichotomy does not correspond to a division in jet power. rather, type ii jets are produced at all observed jet powers, down to the lowest levels in our sample, while type i jets range from very low to moderately high jet powers, with a clear upper bound at l 300mhz ~1043 erg s-1. the range of jet power in each class matches exactly what is expected for efficient (i.e. a few to 100 % eddington) or inefficient ( <0.5% eddington) accretion on to black holes ranging in mass from $10^7{\, {\rm to}\,}10^{9.5}\, {\rm m}_\odot$. | the relativistic jet dichotomy and the end of the blazar sequence |
the properties of quasar-host galaxies might be determined by the growth and feedback of their supermassive black holes (smbhs, 108-10 m⊙). we investigate such connection with a suite of cosmological simulations of massive (halo mass ≈1012 m⊙) galaxies at z ≃ 6 that include a detailed subgrid multiphase gas and accretion model. bh seeds of initial mass 105 m⊙ grow mostly by gas accretion, and become smbh by z = 6 setting on the observed mbh-m⋆ relation without the need for a boost factor. although quasar feedback crucially controls the smbh growth, its impact on the properties of the host galaxy at z = 6 is negligible. in our model, quasar activity can both quench (via gas heating) or enhance (by interstellar medium overpressurization) star formation. however, we find that the star formation history is insensitive to such modulation as it is largely dominated, at least at z > 6, by cold gas accretion from the environment that cannot be hindered by the quasar energy deposition. although quasar-driven outflows can achieve velocities $\gt 1000~\rm km~s^{-1}$, only ≈4 per cent of the outflowing gas mass can actually escape from the host galaxy. these findings are only loosely constrained by available data, but can guide observational campaigns searching for signatures of quasar feedback in early galaxies. | host galaxies of high-redshift quasars: smbh growth and feedback |
we present a multiline survey of the interstellar medium (ism) in two z > 6 quasar host galaxies, pj231−20 (z = 6.59) and pj308−21 (z = 6.23), and their two companion galaxies. observations were carried out using the atacama large (sub-)millimeter array (alma). we targeted 11 transitions including atomic fine-structure lines (fsls) and molecular lines: [nii]205 μm, [ci]369 μm, co (jup = 7, 10, 15, 16), h2o 312 − 221, 321 − 312, 303 − 212, and the oh163 μm doublet. the underlying far-infrared (fir) continuum samples the rayleigh-jeans tail of the respective dust emission. by combining this information with our earlier alma [cii]158 μm observations, we explored the effects of star formation and black hole feedback on the ism of the galaxies using the cloudy radiative transfer models. we estimated dust masses, spectral indexes, ir luminosities, and star-formation rates from the fir continuum. the analysis of the fsls indicates that the [cii]158 μm and [ci]369 μm emission arises predominantly from the neutral medium in photodissociation regions (pdrs). we find that line deficits agree with those of local luminous ir galaxies. the co spectral line energy distributions (sleds) reveal significant high-j co excitation in both quasar hosts. our co sled modeling of the quasar pj231−20 shows that pdrs dominate the molecular mass and co luminosities for jup ≤ 7, while the jup ≥ 10 co emission is likely driven by x-ray dissociation regions produced by the active galactic nucleus (agn) at the very center of the quasar host. the jup > 10 lines are undetected in the other galaxies in our study. the h2o 321 − 312 line detection in the same quasar places this object on the lh2o − ltir relation found for low-z sources, thus suggesting that this water vapor transition is predominantly excited by ir pumping. models of the h2o sled and of the h2o-to-oh163 μm ratio point to pdr contributions with high volume and column density (nh ∼ 0.8 × 105 cm−3, nh = 1024 cm−2) in an intense radiation field. our analysis suggests a less highly excited medium in the companion galaxies. however, the current data do not allow us to definitively rule out an agn in these sources, as suggested by previous studies of the same objects. this work demonstrates the power of multiline studies of fir diagnostics in order to dissect the physical conditions in the first massive galaxies emerging from cosmic dawn. | alma multiline survey of the ism in two quasar host-companion galaxy pairs at z > 6 |
millions of quasar spectra will be collected by the dark energy spectroscopic instrument (desi), leading to a fourfold increase in the number of known quasars. high-accuracy quasar classification is essential to tighten constraints on cosmological parameters measured at the highest redshifts desi observes (z > 2.0). we present spectral templates for identification and redshift estimation of quasars in the desi year 1 data release. the quasar templates are comprised of two quasar eigenspectra sets, trained on spectra from the sloan digital sky survey. the sets are specialized to reconstruct quasar spectral variation observed over separate yet overlapping redshift ranges and, together, are capable of identifying desi quasars from 0.05 < z < 7.0. the new quasar templates show significant improvement over the previous desi quasar templates regarding catastrophic failure rates, redshift precision and accuracy, quasar completeness, and the contamination fraction in the final quasar sample. | performance of the quasar spectral templates for the dark energy spectroscopic instrument |
using a sample of ≃144 000 quasars from the sloan digital sky survey data release 14, we investigate the outflow properties, evident in both absorption and emission, of high-ionization broad absorption line (bal) and non-bal quasars with redshifts 1.6 ≲ z ≤ 3.5 and luminosities 45.3 erg s-1 < log10(lbol) < 48.2 erg s-1. key to the investigation is a continuum and emission-line reconstruction scheme, based on mean-field independent component analysis, that allows the kinematic properties of the c iv λ1550 emission line to be compared directly for both non-bal and bal quasars. c iv emission blueshift and equivalent width (ew) measurements are thus available for both populations. comparisons of the emission-line and bal trough properties reveal strong systematic correlations between the emission and absorption properties. the dependence of quantitative outflow indicators on physical properties such as quasar luminosity and luminosity relative to eddington luminosity is also shown to be essentially identical for the bal and non-bal populations. there is an absence of bals in quasars with the hardest spectral energy distributions (seds), revealed by the presence of strong he ii λ1640 emission, large c iv λ1550 emission ew, and no measurable blueshift. in the remainder of the c iv emission blueshift versus ew space, bal and non-bal quasars are present at all locations; for every bal quasar, it is possible to identify non-bal quasars with the same emission-line outflow properties and sed hardness. the co-location of bal and non-bal quasars as a function of emission-line outflow and physical properties is the key result of our investigation, demonstrating that (high-ionization) bals and non-bals represent different views of the same underlying quasar population. | bal and non-bal quasars: continuum, emission, and absorption properties establish a common parent sample |
we use cosmological hydrodynamical simulations to investigate the role of feedback from accreting black holes in the evolution of the size, compactness, stellar core density, and specific star formation of massive galaxies with stellar masses of {m}* > {10}10.9 {m}⊙ . we perform two sets of cosmological zoom-in simulations of 30 halos to z = 0: (1) without black holes and active galactic nucleus (agn) feedback and (2) with agn feedback arising from winds and x-ray radiation. we find that agn feedback can alter the stellar density distribution, reduce the core density within the central 1 kpc by 0.3 dex from z = 1, and enhance the size growth of massive galaxies. we also find that galaxies simulated with agn feedback evolve along tracks similar to those characterized by observations of specific star formation rate versus compactness. we confirm that agn feedback plays an important role in transforming galaxies from blue compact galaxies into red extended galaxies in two ways: (1) it effectively quenches the star formation, transforming blue compact galaxies into compact quiescent galaxies, and (2) it also removes and prevents new accretion of cold gas, shutting down in situ star formation and causing subsequent mergers to be gas-poor or mixed. gas-poor minor mergers then build up an extended stellar envelope. agn feedback also puffs up the central region through fast agn-driven winds as well as the slow expulsion of gas while the black hole is quiescent. without agn feedback, large amounts of gas accumulate in the central region, triggering star formation and leading to overly massive blue galaxies with dense stellar cores. | the role of black hole feedback on size and structural evolution in massive galaxies |
lyα forest data probing the post-reionization universe show surprisingly large opacity fluctuations over rather large (≥50 h-1 comoving mpc) spatial scales. we model these fluctuations using a hybrid approach utilizing the large-volume millennium simulation to predict the spatial distribution of qsos combined with smaller scale full hydrodynamical simulation performed with ramses and post-processed with the radiative transfer code aton. we produce realistic mock absorption spectra that account for the contribution of galaxies and qsos to the ionizing uv background. these improved models confirm our earlier findings that a significant ( ≳ 50 per cent) contribution of ionizing photons from qsos can explain the large reported opacity fluctuations on large scales. the inferred qso luminosity function is thereby consistent with recent estimates of the space density of qsos at this redshift. our simulations still somewhat struggle, however, to reproduce the very long (110 h-1 comoving mpc) high-opacity absorption through observed in ulas j0148+0600, perhaps suggesting an even later end of reionization than assumed in our previously favoured model. medium-deep/medium area qso surveys as well as targeted searches for the predicted strong transverse qso proximity effect would illuminate the origin of the observed large-scale opacity fluctuations. they would allow us to substantiate whether uv fluctuations due to qso are indeed primarily responsible, or whether significant contributions from other recently proposed mechanisms such as large-scale fluctuations in temperature and mean free path (even in the absence of rare bright sources) are required. | large-scale opacity fluctuations in the lyα forest: evidence for qsos dominating the ionizing uv background at z ∼ 5.5-6? |
strong gravitational lensing provides a powerful test of cold dark matter (cdm) as it enables the detection and mass measurement of low-mass haloes even if they do not contain baryons. compact lensed sources such as active galactic nuclei (agns) are particularly sensitive to perturbing subhaloes, but their use as a test of cdm has been limited by the small number of systems which have significant radio emission that is extended enough to avoid significant lensing by stars in the plane of the lens galaxy, and red enough to be minimally affected by differential dust extinction. narrow-line emission is a promising alternative as it is also extended and, unlike radio, detectable in virtually all optically selected agn lenses. we present first results from a wide field camera 3 (wfc3) grism narrow-line survey of lensed quasars, for the quadruply lensed agn he 0435-1223. using a forward modelling pipeline that enables us to robustly account for spatial blending, we measure the [o iii] 5007 å flux ratios of the four images. we find that the [o iii] fluxes and positions are well fit by a simple smooth mass model for the main lens. our data rule out a m600 > 108(107.2) m⊙ navarro-frenk-white perturber projected within ∼1.0 (0.1) arcsec of each of the lensed images, where m600 is the perturber mass within its central 600 pc. the non-detection is broadly consistent with the expectations of λcdm for a single system. the sensitivity achieved demonstrates that powerful limits on the nature of dark matter can be obtained with the analysis of ∼20 narrow-line lenses. | probing dark matter substructure in the gravitational lens he 0435-1223 with the wfc3 grism |
we study the distribution and kinematics of the cool circumgalactic medium (cgm) of emission line galaxies (elgs) traced by metal absorption lines. using about 200,000 elgs from sdss-iv eboss and half a million background quasars from sdss, we measure the median absorption strength of mg ii and fe ii lines in quasar spectra for impact parameters ranging from 10 kpc to 1 mpc. for comparison, we measure the same quantity around luminous red galaxies (lrgs). on scales greater than 100 kpc both elgs and lrgs exhibit similar absorption profiles. however, metal absorption is 5-10 times stronger around elgs on smaller scales. the metal absorption strength is anisotropic, with an excess along the minor axis of the galaxies, indicating an outflow origin of the absorbing gas. the ratio between the velocity dispersion of the cool cgm and that of its host dark matter halo is about one for elgs but about half for lrgs. these results show that the dichotomy of galaxy types is reflected in both the density distribution and kinematics of the cgm traced by metal absorption lines. our results provide strong evidence that the cgm of elgs is enriched by gas outflows generated by star formation. | the circumgalactic medium of eboss emission line galaxies: signatures of galactic outflows in gas distribution and kinematics |
the supermassive black holes (smbhs) observed at the centers of all massive galaxies are believed to have grown via luminous accretion during quasar phases in the distant past. the fraction of inflowing rest mass energy emitted as light, the radiative efficiency, has been inferred to be 10%, in agreement with expectations from thin disk accretion models. but the existence of billion solar-mass smbhs powering quasars at z > 7 challenges this picture: provided they respect the eddington limit, there is not enough time to grow z > 7 smbhs from stellar remnant seeds unless the radiative efficiency is below 10%. here we show that one can constrain the radiative efficiencies of the most distant quasars known using foreground neutral intergalactic gas as a cosmological-scale ionizing photon counter. from the lyα absorption profiles of ulas j1120+0641 (z = 7.09) and ulas j1342+0928 (z = 7.54), we determine posterior median radiative efficiencies of 0.08% and 0.1%, respectively, and the combination of the two measurements rules out the canonical 10% efficiency at 99.8% credibility after marginalizing over the unknown obscured fraction. this low radiative efficiency implies rapid mass accretion for the earliest smbhs, greatly easing the tension between the age of the universe and the smbh masses. however, our measured efficiency may instead reflect nearly complete obscuration by dusty gas in the quasar host galaxies over the vast majority of their smbh growth. assuming 10% efficiency during unobscured phases, we find that the obscured fraction would be >82% at 95% credibility, and imply a {25.7}-16.5+49.6 times larger obscured than unobscured luminous quasar population at z > 7. | evidence for low radiative efficiency or highly obscured growth of z > 7 quasars |
the growth of the first supermassive black holes (smbhs) at z > 6 is still a major challenge for theoretical models. if it starts from black hole (bh) remnants of population iii stars (light seeds with mass ∼100 m⊙), it requires super-eddington accretion. an alternative route is to start from heavy seeds formed by the direct collapse of gas on to an ∼105 m⊙ bh. here we investigate the relative role of light and heavy seeds as bh progenitors of the first smbhs. we use the cosmological, data constrained semi-analytic model gamete/qsodust to simulate several independent merger histories of z > 6 quasars. using physically motivated prescriptions to form light and heavy seeds in the progenitor galaxies, we find that the formation of a few heavy seeds (between 3 and 30 in our reference model) enables the eddington-limited growth of smbhs at z > 6. this conclusion depends sensitively on the interplay between chemical, radiative and mechanical feedback effects, which easily erase the conditions that allow the suppression of gas cooling in the low-metallicity gas (z < zcr and jlw > jcr). we find that heavy seeds cannot form if dust cooling triggers gas fragmentation above a critical dust-to-gas mass ratio (d ≥ d_cr). in addition, the relative importance of light and heavy seeds depends on the adopted mass range for light seeds, as this dramatically affects the history of cold gas along the merger tree, by both sn- and agn-driven winds. | from the first stars to the first black holes |
we assume that dust near active galactic nuclei (agns) is distributed in a torus-like geometry, which can be described as a clumpy medium or a homogeneous disk, or as a combination of the two (i.e. a two-phase medium). the dust particles considered are fluffy and have higher submillimeter emissivities than grains in the diffuse interstellar medium. the dust-photon interaction is treated in a fully self-consistent three-dimensional radiative transfer code. we provide an agn library of spectral energy distributions (seds). its purpose is to quickly obtain estimates of the basic parameters of the agns, such as the intrinsic luminosity of the central source, the viewing angle, the inner radius, the volume filling factor and optical depth of the clouds, and the optical depth of the disk midplane, and to predict the flux at yet unobserved wavelengths. the procedure is simple and consists of finding an element in the library that matches the observations. we discuss the general properties of the models and in particular the 10 μm silicate band. the agn library accounts well for the observed scatter of the feature strengths and wavelengths of the peak emission. agn extinction curves are discussed and we find that there is no direct one-to-one link between the observed extinction and the wavelength dependence of the dust cross sections. we show that objects in the library cover the observed range of mid-infrared colors of known agns. the validity of the approach is demonstrated by matching the seds of a number of representative objects: four seyferts and two quasars for which we present new herschel photometry, two radio galaxies, and one hyperluminous infrared galaxy. strikingly, for the five luminous objects we find that pure agn models fit the sed without needing to postulate starburst activity. herschel is an esa space observatory with science instruments provided by european-led principal investigator consortia and with important participation from nasa.the sed library of the agn models is 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/583/a120, and at http://www.eso.org/~rsiebenm/agn_models/ | self-consistent two-phase agn torus models⋆. sed library for observers |
1es 1927+654 is a nearby active galactic nucleus (agn) that underwent a changing-look event in early 2018, developing prominent broad balmer lines that were absent in previous observations. we have followed up this object in the x-rays with an ongoing campaign that started in 2018 may and that includes 265 nicer (for a total of 678 ks) and 14 swift/xrt (26 ks) observations, as well as three simultaneous xmm-newton/nustar (158/169 ks) exposures. in the x-rays, 1es 1927+654 shows a behavior unlike any previously known agn. the source is extremely variable both in spectral shape and flux and does not show any correlation between x-ray and uv flux on timescales of hours or weeks/months. after the outburst, the power-law component almost completely disappeared, and the source showed an extremely soft continuum dominated by a blackbody component. the temperature of the blackbody increases with the luminosity, going from kt ~ 80 ev (for a 0.3-2 kev luminosity of l0.3-2 ~ 1041.5 erg s-1) to ~200 ev (for l0.3-2 ~ 1044 erg s-1). the spectra show evidence of ionized outflows and of a prominent feature at ~1 kev, which can be reproduced by a broad emission line. the unique characteristics of 1es 1927+654 in the x-ray band suggest that it belongs to a new type of changing-look agn. future x-ray surveys might detect several more objects with similar properties. | the 450 day x-ray monitoring of the changing-look agn 1es 1927+654 |
we perform a joint bao and rsd analysis using the eboss dr16 lrg and elg samples in the redshift range of z ∈ [0.6, 1.1], and detect an rsd signal from the cross-power spectrum at a ~4σ confidence level, i.e., fσ8 = 0.317 ± 0.080 at zeff = 0.77. based on the chained power spectrum, which is a new development in this work to mitigate the angular systematics, we measure the bao distances and growth rate simultaneously at two effective redshifts, namely, dm/rd (z = 0.70) = 17.96 ± 0.51, dh/rd (z = 0.70) = 21.22 ± 1.20, fσ8 (z = 0.70) = 0.43 ± 0.05, and dm/rd (z = 0.845) = 18.90 ± 0.78, dh/rd (z = 0.845) = 20.91 ± 2.86, fσ8 (z = 0.845) = 0.30 ± 0.08. combined with bao measurements including those from the eboss dr16 qso and lyman-α sample, our measurement has raised the significance level of a non-zero ωλ to ~11σ. the data product of this work is publicly available at https://github.com/icosmology/eboss_dr16_lrgxelg and https://www.sdss.org/science/final-bao-and-rsd-measurements/. | the completed sdss-iv extended baryon oscillation spectroscopic survey: a multitracer analysis in fourier space for measuring the cosmic structure growth and expansion rate |
in this paper, we quantify the ability of multiple measurements of high-redshift quasars to constrain several theories of modified gravity, including the dvali-gabadadze-porrati braneworld scenario, generalized chaplygin gas, f(t) modified gravity, and modified polytropic cardassian model. recently released sample of 1598 quasars with x-ray and ultraviolet flux measurements in the redshift range of 0.036 ≤ z ≤ 5.1003, as well as a compilation of 120 intermediate-luminosity radio quasars covering the redshift of 0.46 < z < 2.76 are respectively used as standard probes at higher redshifts. for all considered modified gravity theories, our results show that there is still some possibility that the standard λ cold dark matter (λcdm) scenario might not be the best cosmological model preferred by the current quasar observations. in order to improve cosmological constraints, the quasar data are also combined with the latest observations of baryon acoustic oscillations, which strongly complement the constraints. finally, we discuss the support given by the data to modified gravity theories, applying different information theoretic techniques like the akaike information criterion, bayesian information criterion, and jensen-shannon divergence. | probing modified gravity theories with multiple measurements of high-redshift quasars |
the ~100 tidal disruption events (tdes) observed so far exhibit a wide range of emission properties both at peak and over their lifetimes. some tdes radiate predominantly at x-ray energies, while others radiate chiefly at uv and optical wavelengths. while the peak luminosities across tdes show distinct properties, the evolutionary behavior can also vary between tdes with similar peak emission properties. in particular, for optical tdes, while their uv and optical emissions decline somewhat following the fallback pattern, some events can greatly rebrighten in x-rays at late time. in this letter, we conduct three-dimensional general relativistic radiation magnetohydrodynamics simulations of tde accretion disks at varying accretion rates in the regime of super-eddington accretion. we make use of monte carlo radiative transfer simulations to calculate the reprocessed spectra at various inclinations and at different evolutionary stages. we confirm the unified model proposed by dai et al., which predicts that the observed emission largely depends on the viewing angle of the observer with respect to the disk orientation. furthermore, we find that disks with higher accretion rates have elevated wind and disk densities, which increases the reprocessing of the high-energy radiation and thus generally augments the optical-to-x-ray flux ratio along a particular viewing angle. this implies that at later times, as the accretion level declines, we expect that more x-rays will leak out along intermediate viewing angles. such dynamical model for tdes can provide a natural explanation for the diversity in the emission properties observed in tdes at peak and along their temporal evolution. | dynamical unification of tidal disruption events |
quasars are associated with and powered by the accretion of material onto massive black holes; the detection of highly luminous quasars with redshifts greater than z = 6 suggests that black holes of up to ten billion solar masses already existed 13 billion years ago. two possible present-day ‘dormant’ descendants of this population of ‘active’ black holes have been found in the galaxies ngc 3842 and ngc 4889 at the centres of the leo and coma galaxy clusters, which together form the central region of the great wall—the largest local structure of galaxies. the most luminous quasars, however, are not confined to such high-density regions of the early universe; yet dormant black holes of this high mass have not yet been found outside of modern-day rich clusters. here we report observations of the stellar velocity distribution in the galaxy ngc 1600—a relatively isolated elliptical galaxy near the centre of a galaxy group at a distance of 64 megaparsecs from earth. we use orbit superposition models to determine that the black hole at the centre of ngc 1600 has a mass of 17 billion solar masses. the spatial distribution of stars near the centre of ngc 1600 is rather diffuse. we find that the region of depleted stellar density in the cores of massive elliptical galaxies extends over the same radius as the gravitational sphere of influence of the central black holes, and interpret this as the dynamical imprint of the black holes. | a 17-billion-solar-mass black hole in a group galaxy with a diffuse core |
we characterize the optical variability of quasars in the palomar transient factory and intermediate palomar transient factory (ptf/iptf) surveys. we re-calibrate the r-band light curves for ∼28,000 luminous, broad-line active galactic nuclei from the sdss, producing a total of ∼2.4 million photometric data points. we utilize both the structure function (sf) and power spectrum density (psd) formalisms to search for links between the optical variability and the physical parameters of the accreting supermassive black holes that power the quasars. the excess variance (sf2) of the quasar sample tends to zero at very short time separations, validating our re-calibration of the time-series data. we find that the the amplitude of variability at a given time-interval, or equivalently the timescale of variability to reach a certain amplitude, is most strongly correlated with luminosity with weak or no dependence on black hole mass and redshift. for a variability level of sf(τ) = 0.07 mag, the timescale has a dependency of τ \propto {l}0.4. this is broadly consistent with the expectation from a simple keplerian accretion disk model, which provides τ \propto {l}0.5. the psd analysis also reveals that many quasar light curves are steeper than a damped random walk. we find a correlation between the steepness of the psd slopes, specifically the fraction of slopes steeper than 2.5, and black hole mass, although we cannot exclude the possibility that luminosity or eddington ratio are the drivers of this effect. this effect is also seen in the sf analysis of the (i)ptf data, and in a psd analysis of quasars in the sdss stripe 82. | optical variability of agns in the ptf/iptf survey |
the hyper suprime-cam subaru strategic program (hsc-ssp) is an excellent survey for the search for strong lenses, thanks to its area, image quality, and depth. we use three different methods to look for lenses among 43000 luminous red galaxies from the baryon oscillation spectroscopic survey (boss) sample with photometry from the s16a internal data release of the hsc-ssp. the first method is a newly developed algorithm, named yattalens, which looks for arc-like features around massive galaxies and then estimates the likelihood of an object being a lens by performing a lens model fit. the second method, chitah, is a modeling-based algorithm originally developed to look for lensed quasars. the third method makes use of spectroscopic data to look for emission lines from objects at a different redshift from that of the main galaxy. we find 15 definite lenses, 36 highly probable lenses, and 282 possible lenses. among the three methods, yattalens, which was developed specifically for this study, performs best in terms of both completeness and purity. nevertheless, five highly probable lenses were missed by yattalens but found by the other two methods, indicating that the three methods are highly complementary. based on these numbers, we expect to find ∼300 definite or probable lenses by the end of the hsc-ssp. | survey of gravitationally-lensed objects in hsc imaging (sugohi). i. automatic search for galaxy-scale strong lenses |
interpreting abundances of damped ly-α absorbers (dlas) from absorption-line spectroscopy has typically been a challenge because of the presence of dust. nevertheless, because dlas trace distant gas-rich galaxies regardless of their luminosity, they provide an attractive way of measuring the evolution of the metallicity of the neutral gas with cosmic time. this has been done extensively so far, but typically not taking proper dust corrections into account. the aims of this paper are to: (i) provide a simplified way of calculating dust corrections, based on a single observed [x/fe], (ii) assess the importance of dust corrections for dla metallicities and their evolution, and (iii) investigate the cosmic evolution of iron for a large dla sample. we have derived dust corrections based on the observed [zn/fe], [si/fe], or [s/fe], and confirmed their robustness. we present dust-corrected metallicities in a scale of [fe/h]tot for 236 dlas over a broad range of z, and assess the extent of dust corrections for different metals at different metallicities. dust corrections in dlas are important even for zn (typically of 0.1-0.2, and up to 0.5 dex), which is often neglected. finally, we study the evolution of the dust-corrected metallicity with z. the dla metallicities decrease with redshift, by a factor of 50-100 from today to 12.6 billion years ago (z = 5). when including dust corrections, the average dla metallicities are 0.4-0.5 dex higher than without corrections. the upper envelope of the relation between metallicity and z reaches solar metallicity at z ≲ 0.5, although some systems can have solar metallicity already out to z 3. based on observations carried out at the european organisation for astronomical research in the southern hemisphere under eso programmes 065.p-0038, 065.o-0063, 066.a-0624, 067.a-0078, and 068.a-0600. | the cosmic evolution of dust-corrected metallicity in the neutral gas |
we test the consistency of active galactic nuclei (agn) optical flux variability with the damped random walk (drw) model. our sample consists of 20 multiquarter kepler agn light curves including both type 1 and 2 seyferts, radio-loud and -quiet agn, quasars, and blazars. kepler observations of agn light curves offer a unique insight into the variability properties of agn light curves because of the very rapid (11.6-28.6 min) and highly uniform rest-frame sampling combined with a photometric precision of 1 part in 105 over a period of 3.5 yr. we categorize the light curves of all 20 objects based on visual similarities and find that the light curves fall into five broad categories. we measure the first-order structure function of these light curves and model the observed light curve with a general broken power-law power spectral density (psd) characterized by a short-time-scale power-law index γ and turnover time-scale τ. we find that less than half the objects are consistent with a drw and observe variability on short time-scales (∼2 h). the turnover time-scale τ ranges from ∼10-135 d. interesting structure function features include pronounced dips on rest-frame time-scales ranging from 10-100 d and varying slopes on different time-scales. the range of observed short-time-scale psd slopes and the presence of dip and varying slope features suggests that the drw model may not be appropriate for all agn. we conclude that agn variability is a complex phenomenon that requires a more sophisticated statistical treatment. | are the variability properties of the kepler agn light curves consistent with a damped random walk? |
we present alma observations of two moderate-luminosity quasars at redshift 6. these quasars, from the canada-france high-z quasar survey (cfhqs), have black hole masses of ∼ {{10}8} {{m}⊙ }. both quasars are detected in the [c ii] line and dust continuum. combining these data with our previous study of two similar cfhqs quasars we investigate the population properties. we show that z\gt 6 quasars have a significantly lower far-infrared (far-ir) luminosity than bolometric-luminosity-matched samples at lower redshift, inferring a lower star formation rate possibly correlated with lower black hole masses at z = 6. the ratios of [c ii] to far-ir luminosities in the cfhqs quasars are comparable to those of starbursts of similar star formation rate in the local universe. we determine the values of velocity dispersion and dynamical mass for the quasar host galaxies based on the [c ii] data. we find that there is no significant offset from the relations defined by nearby galaxies with similar black hole masses. there is, however, a marked increase in the scatter at z = 6, beyond the large observational uncertainties. | star formation rate and dynamical mass of 108 solar mass black hole host galaxies at redshift 6 |
massive galaxies formed most actively at redshifts z = 1-3 during the period known as "cosmic noon." here we present an emission-line study of the extremely red quasar sdssj165202.64+172852.3's host galaxy at z = 2.94, based on observations with the near infrared spectrograph integral field unit on board jwst. we use standard emission-line diagnostic ratios to map the sources of gas ionization across the host and a swarm of companion galaxies. the quasar dominates the photoionization, but we also discover shock-excited regions orthogonal to the ionization cone and the quasar-driven outflow. these shocks could be merger-induced or-more likely, given the presence of a powerful galactic-scale quasar outflow-these are signatures of wide-angle outflows that can reach parts of the galaxy that are not directly illuminated by the quasar. finally, the kinematically narrow emission associated with the host galaxy presents as a collection of 1 kpc-scale clumps forming stars at a rate of at least 200 m ⊙ yr-1. the interstellar medium within these clumps shows high electron densities, reaching up to 3000 cm-3, with metallicities ranging from half to a third solar with a positive metallicity gradient, and v-band extinctions up to 3 mag. the star formation conditions are far more extreme in these regions than in local star-forming galaxies but consistent with those of massive galaxies at cosmic noon. the jwst observations simultaneously reveal an archetypal rapidly forming massive galaxy undergoing a merger, a clumpy starburst, an episode of obscured near-eddington quasar activity, and an extremely powerful quasar outflow. | first results from the jwst early release science program q3d: ionization cone, clumpy star formation, and shocks in a z = 3 extremely red quasar host |
in this paper, we present photometric redshift (photo-z) estimates for the dark energy spectroscopic instrument (desi) legacy imaging surveys, currently the most sensitive optical survey covering the majority of the extragalactic sky. our photo-z methodology is based on a machine-learning approach, using sparse gaussian processes augmented with gaussian mixture models (gmms) that allow regions of parameter space to be identified and trained separately in a purely data-driven way. the same gmms are also used to calculate cost-sensitive learning weights that mitigate biases in the spectroscopic training sample. by design, this approach aims to produce reliable and unbiased predictions for all parts of the parameter space present in wide area surveys. compared to previous literature estimates using the same underlying photometry, our photo-zs are significantly less biased and more accurate at z > 1, with negligible loss in precision or reliability for resolved galaxies at z < 1. our photo-z estimates offer accurate predictions for rare high-value populations within the parent sample, including optically selected quasars at the highest redshifts (z > 6), as well as x-ray or radio continuum selected populations across a broad range of flux (densities) and redshift. deriving photo-z estimates for the full legacy imaging surveys data release 8, the catalogues provided in this work offer photo-z estimates predicted to be of high quality for ≳9 × 108 galaxies over ${\sim}19\, 400\, \text{deg}^{2}$ and spanning 0 < z ≲ 7, offering one of the most extensive samples of redshift estimates ever produced. | all-purpose, all-sky photometric redshifts for the legacy imaging surveys data release 8 |
we investigate the molecular gas content of z ∼ 6 quasar host galaxies using the institut de radioastronomie millimétrique northern extended millimeter array. we targeted the 3 mm dust continuum, and the line emission from co(6-5), co(7-6), and [c i]2−1 in ten infrared-luminous quasars that have been previously studied in their 1 mm dust continuum and [c ii] line emission. we detected co(7-6) at various degrees of significance in all the targeted sources, thus doubling the number of such detections in z ∼ 6 quasars. the 3 mm to 1 mm flux density ratios are consistent with a modified black body spectrum with a dust temperature tdust ∼ 47 k and an optical depth τν = 0.2 at the [c ii] frequency. our study provides us with four independent ways to estimate the molecular gas mass, mh2, in the targeted quasars. this allows us to set constraints on various parameters used in the derivation of molecular gas mass estimates, such as the mass per luminosity ratios αco and α[cii], the gas-to-dust mass ratio δg/d, and the carbon abundance [c]/h2. leveraging either on the dust, co, [c i], or [c ii] emission yields mass estimates of the entire sample in the range mh2 ∼ 1010-1011 m⊙. we compared the observed luminosities of dust, [c ii], [c i], and co(7-6) with predictions from photo-dissociation and x-ray dominated regions. we find that the former provide better model fits to our data, assuming that the bulk of the emission arises from dense (nh > 104 cm−3) clouds with a column density nh ∼ 1023 cm−2, exposed to a radiation field with an intensity of g0 ∼ 103 (in habing units). our analysis reiterates the presence of massive reservoirs of molecular gas fueling star formation and nuclear accretion in z ∼ 6 quasar host galaxies. it also highlights the power of combined 3 mm and 1 mm observations for quantitative studies of the dense gas content in massive galaxies at cosmic dawn. | molecular gas in z ∼ 6 quasar host galaxies |
super-eddington accretion is one scenario that may explain the rapid assembly of ∼109 m⊙ supermassive black holes (bhs) within the first billion year of the universe. this critical regime is associated with radiatively inefficient accretion and accompanied by powerful outflows in the form of winds and jets. by means of hydrodynamical simulations of bh evolution in an isolated galaxy and its host halo with 12 pc resolution, we investigate how super-eddington feedback affects the mass growth of the bh. it is shown that super-eddington feedback efficiently prevents bh growth within a few myr. the super-eddington accretion events remain relatively mild with typical rates of about 2−3 times the eddington limit, because of the efficient regulation by jets in that regime. we find that these jets are powerful enough to eject gas from the centre of the host galaxy all the way up to galactic scales at a few kpc, but do not significantly impact gas inflows at those large scales. by varying the jet feedback efficiency, we find that weaker super-eddington jets allow for more significant bh growth through more frequent episodes of super-eddington accretion. we conclude that effective super-eddington growth is possible, as we find that simulations with weak jet feedback efficiencies provide a slightly larger bh mass evolution over long periods of time (∼80 myr) than that for a bh accreting at the eddington limit. | how the super-eddington regime regulates black hole growth in high-redshift galaxies |
quasar feedback may regulate the growth of supermassive black holes, quench coeval star formation, and impact galaxy morphology and the circumgalactic medium. however, direct evidence for quasar feedback in action at the epoch of peak black hole accretion at z ≈ 2 remains elusive. a good case in point is the z = 1.6 quasar wisea j100211.29+013706.7 (xid 2028), where past analyses of the same ground-based data have come to different conclusions. here, we revisit this object with the integral-field unit of the near infrared spectrograph on board the jwst as part of early release science program q3d. the excellent angular resolution and sensitivity of the jwst data reveal new morphological and kinematic substructures in the outflowing gas plume. an analysis of the emission-line ratios indicates that photoionization by the central quasar dominates the ionization state of the gas with no obvious sign for a major contribution from hot young stars anywhere in the host galaxy. the rest-frame near-uv emission aligned along the wide-angle cone of outflowing gas is interpreted as a scattering cone. the outflow has cleared a channel in the dusty host galaxy, through which some of the quasar ionizing radiation is able to escape and heat the surrounding interstellar and circumgalactic media. although the warm ionized outflow is not powerful enough to impact the host galaxy via mechanical feedback, radiative feedback by the active galactic nucleus, aided by the outflow, may help to explain the unusually small molecular gas mass fraction in the galaxy host. | first results from the jwst early release science program q3d: the warm ionized gas outflow in z 1.6 quasar xid 2028 and its impact on the host galaxy |
we review the current status of knowledge concerning the early phases of star formation during cosmic dawn. this includes the first generations of stars forming in the lowest mass dark matter halos in which cooling and condensation of gas with primordial composition is possible at very high redshift (z >20 ), namely metal-free population iii stars, and the first generation of massive black holes forming at such early epochs, the so-called black hole seeds. the formation of black hole seeds as end states of the collapse of population iii stars, or via direct collapse scenarios, is discussed. in particular, special emphasis is given to the physics of supermassive stars as potential precursors of direct collapse black holes, in light of recent results of stellar evolution models, and of numerical simulations of the early stages of galaxy formation. furthermore, we discuss the role of the cosmic radiation produced by the early generation of stars and black holes at high redshift in the process of reionization. | formation of the first stars and black holes |
we study the interstellar medium in a sample of 27 high-redshift quasar host galaxies at z ≳ 6, using the [c ii] 158 μm emission line and the underlying dust continuum observed at ∼1 kpc resolution with atacama large millimeter array. by performing uv-plane spectral stacking of both the high and low spatial resolution data, we investigate the spatial and velocity extent of gas and the size of the dust-emitting regions. we find that the average surface brightness profile of both the [c ii] and the dust continuum emission can be described by a steep component within a radius of 2 kpc and a shallower component with a scale length of 2 kpc, detected up to ∼10 kpc. the surface brightness of the extended emission drops below ∼1% of the peak at radius of ∼5 kpc, beyond which it constitutes 10%-20% of the total measured flux density. although the central component of the dust continuum emission is more compact than that of the [c ii] emission, the extended components have equivalent profiles. the observed extended components are consistent with those predicted by hydrodynamical simulations of galaxies with similar infrared luminosities, where the dust emission is powered by star formation. the [c ii] gaussian, with no observable [c ii], which would be indicative of outflows. our findings suggest that we are probing the interstellar medium and associated star formation in the quasar host galaxies up to radii of 10 kpc, whereas we find no evidence for halos or outflows. | no evidence for [c ii] halos or high-velocity outflows in z ≳ 6 quasar host galaxies |
observations reveal that quasar host haloes at z ∼ 2 have large covering fractions of cool dense gas (≳60 per cent for lyman limit systems within a projected virial radius). most simulations have so far failed to explain these large observed covering fractions. we analyse a new set of 15 simulated massive haloes with explicit stellar feedback from the fire project, covering the halo mass range mh ≈ 2 × 1012 - 1013 m⊙ at z = 2. this extends our previous analysis of the circum-galactic medium of high-redshift galaxies to more massive haloes. active galactic nuclei (agn) feedback is not included in these simulations. we find lyman limit system covering fractions consistent with those observed around quasars. the large h i covering fractions arise from star formation-driven galactic winds, including winds from low-mass satellite galaxies that interact with cosmological filaments. we show that it is necessary to resolve these satellite galaxies and their winds to reproduce the large lyman limit system covering fractions observed in quasar-mass haloes. our simulations predict that galaxies occupying dark matter haloes of mass similar to quasars but without a luminous agn should have lyman limit system covering fractions comparable to quasars. | a stellar feedback origin for neutral hydrogen in high-redshift quasar-mass haloes |
we explore the cosmological implications of anisotropic clustering measurements of the quasar sample from data release 14 (dr14) of the sloan digital sky survey iv extended baryon oscillation spectroscopic survey (eboss) in configuration space. the {∼ } 147 000 quasar sample observed by eboss offers a direct tracer of the density field and bridges the gap of previous baryon acoustic oscillation measurements between redshift 0.8 < z < 2.2. by analysing the two-point correlation function characterized by clustering wedges ξ _w_i(s) and multipoles ξℓ(s), we measure the angular diameter distance, hubble parameter, and cosmic structure growth rate. we define a systematic error budget for our measurements based on the analysis of n-body simulations and mock catalogues. based on the dr14 large-scale structure quasar sample at the effective redshift zeff = 1.52, we find the growth rate of cosmic structure fσ8(zeff) = 0.396 ± 0.079, and the geometric parameters dv(z)/rd = 26.47 ± 1.23, and fap(z) = 2.53 ± 0.22, where the uncertainties include both statistical and systematic errors. these values are in excellent agreement with the best-fitting standard λ cold dark matter model to the latest cosmic microwave background data from planck. | the clustering of the sdss-iv extended baryon oscillation spectroscopic survey dr14 quasar sample: anisotropic clustering analysis in configuration space |
we investigate the evolution of supermassive black holes in the `evolution and assembly of galaxies and their environments' (eagle) cosmological hydrodynamic simulations. the largest of the eagle volumes covers a (100 cmpc)3 and includes state-of-the-art physical models for star formation and black hole growth that depend only on local gas properties. we focus on the black hole mass function, eddington ratio distribution and the implied duty cycle of nuclear activity. the simulation is broadly consistent with observational constraints on these quantities. in order to make a more direct comparison with observational data, we calculate the soft and hard x-ray luminosity functions of the active galactic nuclei (agn). between redshifts 0 and 1, the simulation is in agreement with data. at higher redshifts, the simulation tends to underpredict the luminosities of the brightest observed agn. this may be due to the limited volume of the simulation, or a fundamental deficiency of the underlying model. it seems unlikely that additional unresolved variability can account for this difference. the simulation shows a similar `downsizing' of the agn population as seen in observational surveys. | supermassive black holes in the eagle universe. revealing the observables of their growth |
there is a large degree of variety in the optical variability of quasars and it is unclear whether this is all attributable to a single (set of) physical mechanism(s). we present the results of a systematic search for major flares in active galactic nucleus (agn) in the catalina real-time transient survey as part of a broader study into extreme quasar variability. such flares are defined in a quantitative manner as being atop of the normal, stochastic variability of quasars. we have identified 51 events from over 900 000 known quasars and high-probability quasar candidates, typically lasting 900 d and with a median peak amplitude of δm = 1.25 mag. characterizing the flare profile with a weibull distribution, we find that nine of the sources are well described by a single-point single-lens model. this supports the proposal by lawrence et al. that microlensing is a plausible physical mechanism for extreme variability. however, we attribute the majority of our events to explosive stellar-related activity in the accretion disc: superluminous supernovae, tidal disruption events and mergers of stellar mass black holes. | understanding extreme quasar optical variability with crts - i. major agn flares |
determining when and how the first galaxies reionised the intergalactic medium promises to shed light on both the nature of the first objects and the cosmic history of baryons. towards this goal, quasar absorption lines play a unique role by probing the properties of diffuse gas on galactic and intergalactic scales. in this review, we examine the multiple ways in which absorption lines trace the connection between galaxies and the intergalactic medium near the reionisation epoch. we first describe how the ly α forest is used to determine the intensity of the ionising ultraviolet background and the global ionising emissivity budget. critically, these measurements reflect the escaping ionising radiation from all galaxies, including those too faint to detect directly. we then discuss insights from metal absorption lines into reionisation-era galaxies and their surroundings. current observations suggest a buildup of metals in the circumgalactic environments of galaxies over z ~ 6 to 5, although changes in ionisation will also affect the evolution of metal line properties. a substantial fraction of metal absorbers at these redshifts may trace relatively low-mass galaxies. finally, we review constraints from the ly α forest and quasar near zones on the timing of reionisation. along with other probes of the high-redshift universe, absorption line data are consistent with a relatively late end to reionisation (5.5 ≲ z ≲ 7); however, the constraints are still fairly week. significant progress is expected to come through improved analysis techniques, increases in the number of known high-redshift quasars from optical and infrared sky surveys, large gains in sensitivity from next-generation observing facilities, and synergies with other probes of the reionisation era. | reionisation and high-redshift galaxies: the view from quasar absorption lines |
following a quasi model-independent approach we measure the transversal bao mode at high redshift using the two-point angular correlation function (2pacf). the analyses done here are only possible now with the quasar catalogue from the twelfth data release (dr12q) from the sloan digital sky survey, because it is spatially dense enough to allow the measurement of the angular bao signature with moderate statistical significance and acceptable precision. our analyses with quasars in the redshift interval z in [2.20,2.25] produce the angular bao scale θbao = 1.77° ± 0.31° with a statistical significance of 2.12 σ (i.e., 97% confidence level), calculated through a likelihood analysis performed using the theoretical covariance matrix sourced by the analytical power spectra expected in the λcdm concordance model. additionally, we show that the bao signal is robust—although with less statistical significance—under diverse bin-size choices and under small displacements of the quasars' angular coordinates. finally, we also performed cosmological parameter analyses comparing the θbao predictions for wcdm and w(a)cdm models with angular bao data available in the literature, including the measurement obtained here, jointly with cmb data. the constraints on the parameters ωm, w0 and wa are in excellent agreement with the λcdm concordance model. | angular baryon acoustic oscillation measure at z=2.225 from the sdss quasar survey |
the time delays of gravitationally lensed quasars are generally believed to be unique numbers whose measurement is limited only by the quality of the light curves and the models for the contaminating contribution of gravitational microlensing to the light curves. this belief is incorrect - gravitational microlensing also produces changes in the actual time delays on the ∼day(s) light-crossing time-scale of the emission region. this is due to a combination of the inclination of the disc relative to the line of sight and the differential magnification of the temperature fluctuations producing the variability. we demonstrate this both mathematically and with direct calculations using microlensing magnification patterns. measuring these delay fluctuations can provide a physical scale for microlensing observations, removing the need for priors on either the microlens masses or the component velocities. that time delays in lensed quasars are themselves time variable likely explains why repeated delay measurements of individual lensed quasars appear to vary by more than their estimated uncertainties. this effect is also a new important systematic problem for attempts to use time delays in lensed quasars for cosmology or to detect substructures (satellites) in lens galaxies. | microlensing makes lensed quasar time delays significantly time variable |
we constrain and update the bounds on the lifetime of a decaying dark matter model with a warm massive daughter particle using the most recent low-redshift probes. we use supernovae type-ia, baryon acoustic oscillations and the time delay measurements of gravitationally lensed quasars. these data sets are complemented by the early universe priors taken from the cosmic microwave background. for the maximum allowed fraction of the relativistic daughter particle, the updated bounds on the lifetime are found to be $\tau \gt 9\, \rm {gyr}$ and $\tau \gt 11\, \rm {gyr}$ at $95{{\ \rm per\ cent}}$ c.l., for the two-body and many-body decay scenarios, respectively. we also comment on the recent proposal that the current two-body decaying dark matter model can provide resolution for the h0-tension, by contrasting against the standard λcdm model. we infer that the current dark matter decaying scenario is unlikely to alleviate the h0-tension. we find that the decaying dark matter is able to reduce the trend of the decreasing h0 values with increasing lens redshifts observed in the strong lensing data set. | late-time decaying dark matter: constraints and implications for the h0-tension |
accretion discs around active galactic nuclei (agns) are potentially unstable to star formation at large radii. we note that when the compact objects formed from some of these stars spiral into the central supermassive black hole (smbh), there is no radiative feedback and therefore the accretion rate is not limited by radiation forces. using a set of accretion disc models, we calculate the accretion rate on to the central smbh in both gas and compact objects. we find that the time-scale for an smbh to double in mass can decrease by factors ranging from ∼0.7 to as low as ∼0.1 in extreme cases, compared to gas accretion alone. our results suggest that the formation of extremely massive black holes at high redshift may occur without prolonged super-eddington gas accretion or very massive seed black holes. we comment on potential observational signatures as well as implications for other observations of agns. | star formation in accretion discs and smbh growth |
using our cosmological radiative transfer code, we study the implications of the updated quasi-stellar object (qso) emissivity and star formation history for the escape fraction (fesc) of hydrogen ionizing photons from galaxies. we estimate the fesc that is required to reionize the universe and to maintain the ionization state of the intergalactic medium in the post-reionization era. at z > 5.5, we show that a constant fesc of 0.14-0.22 is sufficient to reionize the universe. at z < 3.5, consistent with various observations, we find that fesc can have values from 0 to 0.05. however, a steep rise in fesc, of at least a factor of ∼3, is required between z = 3.5 and 5.5. it results from a rapidly decreasing qso emissivity at z > 3 together with a nearly constant measured h i photoionization rates at 3 < z < 5. we show that this requirement of a steep rise in fesc over a very short time can be relaxed if we consider the contribution from a recently found large number density of faint qsos at z ≥ 4. in addition, a simple extrapolation of the contribution of such qsos to high-z suggests that qsos alone can reionize the universe. this implies, at z > 3.5, that either the properties of galaxies should evolve rapidly to increase the fesc or most of the low-mass galaxies should host massive black holes and sustain accretion over a prolonged period. these results motivate a careful investigation of theoretical predictions of these alternate scenarios that can be distinguished using future observations. moreover, it is also very important to revisit the measurements of h i photoionization rates that are crucial to the analysis presented here. | the redshift evolution of escape fraction of hydrogen ionizing photons from galaxies |
stellar-mass black hole binaries (bhbs) near supermassive black holes (smbh) in galactic nuclei undergo eccentricity oscillations due to gravitational perturbations from the smbh. previous works have shown that this channel can contribute to the overall bhb merger rate detected by the laser interferometer gravitational-wave observatory (ligo) and virgo interferometer. significantly, the smbh gravitational perturbations on the binary’s orbit may produce eccentric bhbs which are expected to be visible using the upcoming laser interferometer space antenna (lisa) for a large fraction of their lifetime before they merge in the ligo/virgo band. for a proof of concept, we show that the eccentricity oscillations of these binaries can be detected with lisa for bhbs in the local universe up to a few megaparsecs, with observation periods shorter than the mission lifetime, thereby disentangling this merger channel from others. the approach presented here is straightforward to apply to a wide variety of compact object binaries with a tertiary companion. | detecting supermassive black hole-induced binary eccentricity oscillations with lisa |
discrepancies between reported structure function (sf) slopes and their overall flatness as compared to the expectations from the damped random walk (drw) model, which generally well describes the variability of active galactic nuclei (agns), have triggered us to study this problem in detail. we review common agn variability observables and identify their most common problems. equipped with this knowledge, we study ∼9000 r-band agn light curves from stripe 82 of the sloan digital sky survey, using sfs described by stochastic processes with the power exponential covariance matrix of the signal. we model the “subensemble” sfs in the redshift-absolute magnitude bins with the full sf equation (including the turnover and the noise part) and a single power law (spl; in the “red noise regime” after subtracting the noise term). the distribution of full-equation sf (spl) slopes peaks at γ =0.55+/- 0.08 (0.52 ± 0.06) and is consistent with the drw model. there is a hint of a weak correlation of γ with the luminosity and a lack of correlation with the black hole mass. the typical decorrelation timescale in the optical is τ =0.97+/- 0.46 year. the sf amplitude at one year obtained from the spl fitting is {{sf}}0=0.22+/- 0.06 mag and is overestimated because the sf is already at the turnover part, so the true value is {{sf}}0=0.20+/- 0.06 mag. the asymptotic variability is {{sf}}∞ =0.25+/- 0.06 mag. it is strongly anticorrelated with both the luminosity and the eddington ratio and is correlated with the black hole mass. the reliability of these results is fortified with monte carlo simulations. | revisiting stochastic variability of agns with structure functions |
using a bayesian framework, we quantify what current observations imply about the history of the epoch of reionization (eor). we use a popular, three-parameter eor model, flexible enough to accommodate a wide range of physically plausible reionization histories. we study the impact of various eor observations: (i) the optical depth to the cmb measured by planck 2016; (ii) the dark fraction in the lyman α and β forests; (iii) the redshift evolution of galactic lyα emission (so-called 'lyα fraction'); (iv) the clustering of lyα emitters; (v) the igm damping wing imprint in the spectrum of qso ulasj1120+0641; (vi) and the patchy kinetic sunyaev-zel'dovich signal. combined, (i) and (ii) already place interesting constraints on the reionization history, with the epochs corresponding to an average neutral fraction of (75, 50, 25) per cent, constrained at 1σ to z= (9.21^{+1.22 }_{ -1.15}, 8.14^{+1.08 }_{ -1.00}, 7.26^{+1.13 }_{ -0.96}). folding-in more model-dependent eor observations [(iii)-(vi)], strengthens these constraints by tens of per cent, at the cost of a decrease in the likelihood of the best-fitting model, driven mostly by (iii). the tightest constraints come from (v). unfortunately, no current observational set is sufficient to break degeneracies and constrain the astrophysical eor parameters. however, model-dependent priors on the eor parameters themselves can be used to set tight limits by excluding regions of parameter space with strong degeneracies. motivated by recent observations of z ∼ 7 faint, lensed galaxies, we show how a conservative upper limit on the virial temperature of haloes which host reionizing galaxies can constrain the escape fraction of ionizing photons to f_esc = 0.14^{+0.26 }_{ -0.09}. | the global history of reionization |
recent observations of extreme variability in active galactic nuclei have pushed standard viscous accretion disk models over the edge. i suggest either that some kind of non-local physics dominates accretion disks, or that the optical output we see comes entirely from reprocessing a central source. | quasar viscosity crisis |
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