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we present new ultraviolet, optical, and x-ray data on the phoenix galaxy cluster (spt-clj2344-4243). deep optical imaging reveals previously undetected filaments of star formation, extending to radii of ∼50-100 kpc in multiple directions. combined uv-optical spectroscopy of the central galaxy reveals a massive (2 × 109 m⊙), young (∼4.5 myr) population of stars, consistent with a time-averaged star formation rate of 610 ± 50 m⊙ yr-1. we report a strong detection of o vi λλ1032,1038, which appears to originate primarily in shock-heated gas, but may contain a substantial contribution (>1000 m⊙ yr-1) from the cooling intracluster medium (icm). we confirm the presence of deep x-ray cavities in the inner ∼10 kpc, which are among the most extreme examples of radio-mode feedback detected to date, implying jet powers of 2-7 × 1045 erg s-1. we provide evidence that the active galactic nucleus inflating these cavities may have only recently transitioned from “quasar-mode” to “radio-mode,” and may currently be insufficient to completely offset cooling. a model-subtracted residual x-ray image reveals evidence for prior episodes of strong radio-mode feedback at radii of ∼100 kpc, with extended “ghost” cavities indicating a prior epoch of feedback roughly 100 myr ago. this residual image also exhibits significant asymmetry in the inner ∼200 kpc (0.15r500), reminiscent of infalling cool clouds, either due to minor mergers or fragmentation of the cooling icm. taken together, these data reveal a rapidly evolving cool core which is rich with structure (both spatially and in temperature), is subject to a variety of highly energetic processes, and yet is cooling rapidly and forming stars along thin, narrow filaments. | deep chandra, hst-cos, and megacam observations of the phoenix cluster: extreme star formation and agn feedback on hundred kiloparsec scales |
the intrinsic column density (nh) distribution of quasars is poorly known. at the high obscuration end of the quasar population and for redshifts z < 1, the x-ray spectra can only be reliably characterized using broad-band measurements that extend to energies above 10 kev. using the hard x-ray observatory nustar, along with archival chandra and xmm-newton data, we study the broad-band x-ray spectra of nine optically selected (from the sdss), candidate compton-thick (nh > 1.5 × 1024 cm-2) type 2 quasars (ctqso2s); five new nustar observations are reported herein, and four have been previously published. the candidate ctqso2s lie at z < 0.5, have observed [o iii] luminosities in the range 8.4\lt {log}({l}[{{o} {{iii}}]}/{l}⊙ )\lt 9.6, and show evidence for extreme, compton-thick absorption when indirect absorption diagnostics are considered. among the nine candidate ctqso2s, five are detected by nustar in the high-energy (8-24 kev) band: two are weakly detected at the ≈3σ confidence level and three are strongly detected with sufficient counts for spectral modeling (≳90 net source counts at 8-24 kev). for these nustar-detected sources direct (i.e., x-ray spectral) constraints on the intrinsic active galactic nucleus properties are feasible, and we measure column densities ≈2.5-1600 times higher and intrinsic (unabsorbed) x-ray luminosities ≈10-70 times higher than pre-nustar constraints from chandra and xmm-newton. assuming the nustar-detected type 2 quasars are representative of other compton-thick candidates, we make a correction to the nh distribution for optically selected type 2 quasars as measured by chandra and xmm-newton for 39 objects. with this approach, we predict a compton-thick fraction of {f}{ct}={36}-12+14 %, although higher fractions (up to 76%) are possible if indirect absorption diagnostics are assumed to be reliable. | nustar reveals extreme absorption in z < 0.5 type 2 quasars |
in this work, we investigate the reliability of the bpt diagram for excluding galaxies that host an active galactic nucleus (agn). we determine the prevalence of x-ray agns in the star-forming region of the bpt diagram and discuss the reasons behind this apparent misclassification, focusing primarily on relatively massive ({log}({m}* )≳ 10) galaxies. x-ray agns are selected from deep xmm observations using a new method that results in greater samples with a wider range of x-ray luminosities, complete to {log}({l}{{x}})> 41 for z < 0.3. taking x-ray detectability into account, we find that the average fraction of x-ray agns in the bpt star-forming branch is 2%, suggesting the bpt diagram can provide a reasonably clean sample of star-forming galaxies. however, the x-ray selection is itself rather incomplete. at the tip of the agn branch of the bpt diagram, the x-ray agn fraction is only 14%, which may have implications for studies that exclude agns based only on x-ray observations. interestingly, the x-ray agn fractions are similar for seyfert and liner populations, consistent with liners being true agns. we find that neither the star formation dilution nor the hidden broad-line components can satisfactorily explain the apparent misclassification of x-ray agns. on the other hand, ∼40% of all x-ray agns have weak emission lines such that they cannot be placed on the bpt diagram at all and often have low specific sfrs. therefore, the most likely explanation for “misclassified” x-ray agns is that they have intrinsically weak agn lines, and are only placeable on the bpt diagram when they tend to have high specific sfrs. | crossing the line: active galactic nuclei in the star-forming region of the bpt diagram |
we present measurements of the large-scale (≈40 comoving mpc) effective optical depth of he ii lyα absorption, {τ }eff}, at 2.54 < z < 3.86 toward 16 he ii-transparent quasars observed with the cosmic origins spectrograph on the hubble space telescope, to characterize the ionization state of helium in the intergalactic medium (igm). we provide the first statistical sample of {τ }eff} measurements in six signal-to-noise ratio ≳3 he ii sightlines at z > 3.5, and study the redshift evolution and sightline-to-sightline variance of {τ }eff} in 24 he ii sightlines. we confirm an increase of the median {τ }eff} from ≃2 at z = 2.7 to {τ }eff}≳ 5 at z > 3, and a scatter in {τ }eff} that increases with redshift. the z > 3.5 he ii absorption is predominantly saturated, but isolated narrow (δv < 650 km s-1) transmission spikes indicate patches of reionized helium. we compare our measurements to predictions for a range of uv background models applied to outputs of a large-volume (146 comoving mpc)3 hydrodynamical simulation by forward-modeling our sample’s quality and size. at z > 2.74, the variance in {τ }eff} significantly exceeds expectations for a spatially uniform uv background, but is consistent with a fluctuating radiation field sourced by variations in the quasar number density and the mean free path in the post-reionization igm. we develop a method to infer the approximate median he ii photoionization rate {{{γ }}}he{{ii}}} of a fluctuating uv background from the median {τ }eff}, finding a factor ≃5 decrease in {{{γ }}}he{{ii}}} between z ≃ 2.6 and z ≃ 3.1. at z ≃ 3.1, {{{γ }}}he{{ii}}}=≤ft[{9.1}-1.2+1.1 ({stat}.){ }-3.4+2.4 ({sys}.)\right]× {10}-16 s-1 corresponds to a median he ii fraction of ≃2.5%, indicating that our data probe the tail end of he ii reionization. based on observations made with the nasa/esa hubble space telescope, obtained at the space telescope science institute, which is operated by the association of universities for research in astronomy, inc., under nasa contract nas5-26555. these observations are associated with programs 13013 and 13875. archival hubble space telescope data (programs 7575, 9350, 11528, 12033, 12178, 12249, 12816) were obtained from the mikulski archive for space telescopes (mast). | the evolution of the he ii-ionizing background at redshifts 2.3 < z < 3.8 inferred from a statistical sample of 24 hst/cos he ii lyα absorption spectra |
the lifetime of quasars can be estimated by means of their proximity zone sizes, which are regions of enhanced flux blueward of the lyα emission line observed in the rest-frame uv spectra of high-redshift quasars because the intergalactic gas has a finite response time to the quasars' radiation. we estimate the effective lifetime of the high-redshift quasar population from the composite transmitted flux profile within the proximity zone region of a sample of 15 quasars at 5.8 ≤ z ≤ 6.6 with precise systemic redshifts, and similar luminosities, i.e., -27.6 ≤ m1450 ≤ -26.4, and thus a similar instantaneous ionizing power. we develop a bayesian method to infer the effective lifetime from the composite spectrum, including robust estimates of various sources of uncertainty on the spectrum. we estimate an effective lifetime of the quasar population as a whole of ${\mathrm{log}}_{10}({t}_{{\rm{q}}}/\mathrm{yr})={5.7}_{-0.3(-0.5)}^{+0.5(+0.8)}$ given by the median and 68th (95th) percentile of the posterior probability distribution. while our result is consistent with previous quasar lifetime studies, it poses significant challenges on the current model for the growth of supermassive black holes located in the center of the quasars' host galaxies, which requires that quasar lifetimes are more than an order of magnitude longer. | estimating the effective lifetime of the z 6 quasar population from the composite proximity zone profile |
we present results from a polarization study of the radio-intermediate quasar, iii zw 2, at a redshift of 0.089, with the upgraded giant metrewave radio telescope (ugmrt) at 685 mhz and the karl g. jansky very large array (vla) at 5 and 34 ghz. we detect a kpc-scale outflow, exhibiting transverse magnetic (b-) fields. the curved jet terminates in a bow-shock-like radio structure with inferred b-fields aligned with the lobe edges. we suggest that the radio outflow in iii zw 2 is a combination of a collimated jet along with a wind-like component. this 'wind' component could be a magnetized accretion disc wind or the outer layers of a broadened jet or a combination of both. the current data cannot differentiate between these possibilities. we also detect kpc-scale lobe emission that is misaligned with the primary lobes in the ugmrt images. the spectral indices and the electron lifetimes in the misaligned lobe are similar to the primary lobe, suggesting that the misaligned lobe is not a relic. we propose that changing spectral states of the accretion disc, and the subsequent intermittent behaviour of the outflow, along with the close interplay between the jet and 'wind' could explain the radio-intermediate nature of iii zw 2. our study shows that radio-intermediate quasars are promising sources for understanding the role of jets and winds in galaxy evolution and demonstrates the power of radio polarization studies towards achieving this. | outflows in the radio-intermediate quasar iii zw 2: a polarization study with the evla and ugmrt |
we broadly explore the effects of systematic errors on reverberation mapping lag uncertainty estimates from javelin and the interpolated cross-correlation function (iccf) method. we focus on simulated light curves from random realizations of the light curves of five intensively monitored agns. both methods generally work well even in the presence of systematic errors, although javelin generally provides better error estimates. poorly estimated light-curve uncertainties have less effect on the iccf method because, unlike javelin , it does not explicitly assume gaussian statistics. neither method is sensitive to changes in the stochastic process driving the continuum or the transfer function relating the line light curve to the continuum. the only systematic error we considered that causes significant problems is if the line light curve is not a smoothed and shifted version of the continuum light curve but instead contains some additional sources of variability. | on reverberation mapping lag uncertainties |
we review the properties of the established scaling relations (srs) of galaxies and active galactic nuclei (agn), focusing on their origin and expected evolution back in time, providing a short history of the most important progresses obtained up to now and discussing the possible future studies. we also try to connect the observed srs with the physical mechanisms behind them, examining to what extent current models reproduce the observational data. the emerging picture clarifies the complexity intrinsic to the galaxy formation and evolution process as well as the basic uncertainties still affecting our knowledge of the agn phenomenon. at the same time, however, it suggests that the detailed analysis of the srs can profitably contribute to our understanding of galaxies and agn. | past, present and future of the scaling relations of galaxies and active galactic nuclei |
we present a suite of high-resolution cosmological zoom-in simulations to z = 4 of a 1012 m⊙ halo at z = 0, obtained using seven contemporary astrophysical simulation codes (art-i, enzo, ramses, changa, gadget-3, gear, and gizmo) widely used in the numerical galaxy formation community. the physics prescriptions for gas cooling and heating and star formation are the same as the ones used in our previous assembling galaxies of resolved anatomy (agora) disk comparison but now account for the effects of cosmological processes such as the expansion of the universe, intergalactic gas inflow, and the cosmic ultraviolet background radiation emitted by massive stars and quasars. in this work, we introduce the most careful comparison yet of galaxy formation simulations run by different code groups, together with a series of four calibration steps each of which is designed to reduce the number of tunable simulation parameters adopted in the final run. in the first two steps, we methodically calibrate the gas physics, such as cooling and heating, in simulations without star formation. in the third step, we seek agreement on the total stellar mass produced with the common star formation prescription used in the agora disk comparison, in stellar-feedback-free simulations. in the last calibration step, we activate stellar feedback, where each code group is asked to set the feedback prescription to as close to the most widely used one in its code community as possible, while aiming for convergence in the stellar mass at z = 4 to the values predicted by semiempirical models. after all the participating code groups successfully complete the calibration steps, we achieve a suite of cosmological simulations with similar mass assembly histories down to z = 4. with numerical accuracy that resolves the internal structure of a target halo (≲100 physical pc at z = 4), we find that the codes overall agree well with one another, e.g., in gas and stellar properties, but also show differences, e.g., in circumgalactic medium (cgm) properties. we argue that, if adequately tested in accordance with our proposed calibration steps and common parameters, high-resolution cosmological zoom-in simulations can have robust and reproducible results. new code groups are invited to join and enrich this comparison by generating equivalent models or to test the code's compatibility on their own, by adopting the common initial conditions, the common easy-to-implement physics package, and the proposed calibration steps. further analyses of the zoom-in simulations presented here will be presented in forthcoming reports from the agora collaboration, including studies of the cgm, simulations by additional codes, and results at lower redshift. | the agora high-resolution galaxy simulations comparison project. iii. cosmological zoom-in simulation of a milky way-mass halo |
the late-time integrated sachs-wolfe (isw) imprint of $r\gtrsim 100~h^{-1}\, \mathrm{mpc}$ superstructures is sourced by evolving large-scale potentials due to a dominant dark energy component in the λcdm model. the aspect that makes the isw effect distinctly interesting is the repeated observation of stronger-than-expected imprints from supervoids at z ≲ 0.9. here we analyse the un-probed key redshift range 0.8 < z < 2.2 where the isw signal is expected to fade in λcdm, due to a weakening dark energy component, and eventually become consistent with zero in the matter dominated epoch. on the contrary, alternative cosmological models, proposed to explain the excess low-z isw signals, predicted a sign-change in the isw effect at z ≈ 1.5 due to the possible growth of large-scale potentials that is absent in the standard model. to discriminate, we estimated the high-z λcdm isw signal using the millennium xxl mock catalogue, and compared it to our measurements from about 800 supervoids identified in the eboss dr16 quasar catalogue. at 0.8 < z < 1.2, we found an excess isw signal with aisw ≈ 3.6 ± 2.1 amplitude. the signal is then consistent with the λcdm expectation (aisw = 1) at 1.2 < z < 1.5 where the standard and alternative models predict similar amplitudes. most interestingly, we also observed an opposite-sign isw signal at 1.5 < z < 2.2 that is in 2.7σ tension with the λcdm prediction. taken at face value, these recurring hints for isw anomalies suggest an alternative growth rate of structure in low-density environments at $\sim 100~h^{-1}\, \mathrm{mpc}$ scales. | evidence for a high-z isw signal from supervoids in the distribution of eboss quasars |
we present the results of our spatially resolved investigation into the interplay between the ages of the stellar populations and the kinematics of the warm ionized outflows in the well-studied type ii quasar markarian 34 (mrk 34). utilizing integral field spectroscopy data, we determine the spatial distribution of the young stellar population (ysp; tysp < 100 myr) using spectral synthesis modelling. we also employ the [o iii] λ5007 emission line as a tracer of the warm ionized gas kinematics. we demonstrate a spatial correlation between the outer edges of the blue side of the outflow and an enhancement in the proportion of the ysp flux, suggesting that the outflow is responsible for triggering star formation in this region. in regions with more highly disrupted gas kinematics, we find that the proportion of ysp flux is consistent with that found outside the outflow region, suggesting that the increased disruption is preventing a similar enhancement in star formation from occurring. our analysis suggests that mrk 34 is an example of quasar-driven outflows simultaneously producing both 'positive' and 'preventive' feedback, further demonstrating the complex nature of the relationship between quasars and their host galaxies. | spatially resolved evidence of the impact of quasar-driven outflows on recent star formation: the case of mrk 34 |
using bona-fide black hole (bh) mass estimates from reverberation mapping and the line ratio [si vi] 1.963$\rm{\mu m}$/brγbroad as tracer of the agn ionizing continuum, a novel bh-mass scaling relation of the form log(mbh) = (6.40 ± 0.17) - (1.99 ± 0.37) × log ([si vi]/brγbroad), dispersion 0.47 dex, over the bh mass interval, 106-108 m⊙ is found. following on the geometrically thin accretion disc approximation and after surveying a basic parameter space for coronal lines production, we believe one of main drivers of the relation is the effective temperature of the disc, which is effectively sampled by the [si vi] 1.963$\rm{\mu m}$ coronal line for the range of bh masses considered. by means of cloudy photoionization models, the observed anticorrelation appears to be formally in line with the thin disc prediction tdisc ∝ mbh-1/4. | a novel black hole mass scaling relation based on coronal gas, and its dependence with the accretion disc |
quasar outflows may play a crucial role in regulating the host galaxy, although the spatial scale of quasar outflows remain a major enigma, with their acceleration mechanism poorly understood. the kinematic information of outflow is the key to understanding its origin and acceleration mechanism. here, we report the galactocentric distances of different outflow components for both a sample and an individual quasar. we find that the outflow distance increases with velocity, with a typical value from several parsecs to more than one hundred parsecs, providing direct evidence for an acceleration happening at a scale of the order of 10 parsecs. these outflows carry ∼1% of the total quasar energy, while their kinematics are consistent with a dust-driven model with a launching radius comparable to the scale of a dusty torus, indicating that the coupling between dust and quasar radiation may produce powerful feedback that is crucial to galaxy evolution. active supermassive black holes sweep out the dusty gas around it tens of light years away, forming powerful fast outflows. | evidence for quasar fast outflows being accelerated at the scale of tens of parsecs |
we have recently found fundamental differences in the radio properties of red quasars when compared to typical blue quasars. in this paper, we use data from the x-shooter spectrograph on the very large telescope, providing spectral coverage from ~3000-$25\,000\,$ å, of a sample of 40 red and blue luminous quasars at 1.45 < z < 1.65 to explore the connections between the radio, emission-line, and accretion-disc properties. we fit various dust-extinction curves to the data and find that dust reddening can fully explain the observed colours for the majority of the red quasars in our sample, with moderate extinctions ranging from av ~ 0.06-0.7 mag. we confront our spectra with a simple thin accretion-disc model and find this can describe the continua of both the blue and red quasars, once corrected for dust extinction; we also find no significant differences in the accretion properties. we detect ionized outflows in a number of red and blue quasars, but do not find any significant evidence that they are more prevalent in the red quasar population. overall our findings imply that the radio emission is more closely connected to circumnuclear/ism opacity rather than accretion disc or outflow differences. | fundamental differences in the properties of red and blue quasars: measuring the reddening and accretion properties with x-shooter |
we present a strong lensing analysis of the galaxy cluster sdss j1029+2623 at z = 0.588, one of the few currently known lens clusters with multiple images of a background (z = 2.1992) quasar with a measured time delay. we use archival hubble space telescope multiband imaging and new multi unit spectroscopic explorer follow-up spectroscopy to build an accurate lens mass model, a crucial step toward future cosmological applications. the spectroscopic data enable the secure identification of 57 cluster members and of two nearby perturbers along the line of sight. we estimate the inner kinematics of a subset of 20 cluster galaxies to calibrate the scaling relations parameterizing the sub-halo mass component. we also reliably determine the redshift of four multiply imaged sources, provide a tentative measurement for one system, and report the discovery of a new four-image system. the final catalog comprises 26 multiple images from seven background sources, spanning a wide redshift range, from 1.02 to 5.06. we present two parametric lens models, with slightly different cluster mass parameterizations. the observed positions of the multiple images are accurately reproduced within approximately 0.″2, the three image positions of the quasar within only ~0.″1. we estimate a cluster projected total mass of m(<300 kpc) ~ 2.1 × 1014 m ⊙, with a statistical uncertainty of a few percent. both models, which include a small galaxy close to one of the quasar images, predict magnitude differences and time delays between the quasar images that are consistent with the observations. * this work is based in large part on data collected at the eso vlt (prog. id 0102.a-0642(a)) and the nasa hst. | vlt/muse observations of sdss j1029+2623: toward a high-precision strong lensing model |
recent results of ground-based telescopes, giving high-quality measurements of the cosmic microwave background (cmb) temperature power spectrum on small scales (below 1 deg) motivate the need for an accurate model of foregrounds, which dominate the primary signal at these multipoles. in a previous work, we have shown that cosmological information could be retrieved from the power spectrum of the thermal sunyaev zel'dovich (sz) effect. in this work, we introduce a physically motivated model of the epoch of reionisation in the cosmological analysis of cmb data, which is coherent on all scales. in particular, at high multipoles, the power spectrum of the kinetic sz (ksz) effect is inferred from a set of cosmological and reionisation parameters by a machine-learning algorithm. first including an asymmetric parameterisation of the reionisation history in the planck 2018 data analysis, we retrieve a value of the thomson optical depth consistent with previous results, but stemming from a completely different history of reionisation in which the first luminous sources light up as early as z = 15. considering the latest small-scale data from the south pole telescope (spt) and letting the cosmology free to vary, we find that including the new cosmology-dependent tsz and ksz spectra helps tighten the constraints on their amplitudes by breaking their degeneracy. we report a 5σ measurement of the ksz signal at ℓ = 3000, d3000ksz = 3.4−0.3+0.5 μk2 at the 68% confidence level (c.l.), marginalised over cosmology, as well as an upper limit on the patchy signal from reionisation d3000pksz < 1.6 μk2 (95% c.l.). additionally, we find that the spt data favour slightly earlier reionisation scenarios than planck, leading to τ = 0.062−0.015+0.012 and a reionisation midpoint zre = 7.9−1.3+1.1 (68% c.l.), which is in line with constraints from high-redshift quasars and galaxies. | retrieving cosmological information from small-scale cmb foregrounds. ii. the kinetic sunyaev zel'dovich effect |
context. the strong asymmetry in the optical [o iii] λ5007 emission line is one of the best signatures of active galactic nuclei (agn) driven warm (∼104 k) ionized gas outflows on host galaxy scales. while large spectroscopic surveys such as the sloan digital sky survey (sdss) have characterized the kinematics of [o iii] for large samples of agn, estimating the associated energetics requires spatially resolving these outflows with, for example, integral field unit (ifu) studies.aims: as part of the close agn reference survey, we obtained spatially resolved ifu spectroscopy for a representative sample of 39 luminous type 1 agn at 0.01 < z < 0.06 with the multi unit spectroscopic explorer and the visible multi object spectrograph ifus at the very large telescope to infer the spatial location of the ionized gas outflows.methods: we compared the 2d light distributions of the [o iii] wing to that of the hβ broad emission line region, a classical point source (psf). we then used the psf to distinguish between the unresolved and resolved [o iii] wing emission. we further determined its location using spectro-astrometry for the point-like sources.results: the [o iii] wing is spatially unresolved in 23 out of the 36 agn with > 80% of the flux associated with a point-like source. we measured < 100 pc offsets in the spatial location of the outflow from the agn nucleus using the spectro-astrometry technique for these sources. for the other 13 agn, the [o iii] wing emission is resolved and possibly extended on several kiloparsec scales.conclusions: we conclude that [o iii] wing emission can be compact or extended in an unbiased luminous agn sample, where both cases are likely to appear. electron density in the compact [o iii] wing regions (median ne ∼ 1900 cm−3) is nearly a magnitude higher than in the extended ones (median ne ∼ 500 cm−3). the presence of spatially extended and compact [o iii] wing emission is unrelated to the agn bolometric luminosity and to inclination effects, which means other features such as time delays, or mechanical feedback (radio jets) may shape the ionized gas outflow properties. | the close agn reference survey (cars). locating the [o iii] wing component in luminous local type 1 agn |
cosmography is used in cosmological data processing in order to constrain the kinematics of the universe in a model-independent way. in this paper, we first investigate the effect of the ultraviolet (uv) and x-ray relation of a quasar on cosmological constraints. by fitting the quasar relation and cosmographic parameters simultaneously, we find that the 4σ deviation from the cosmological constant λ cold dark matter (λcdm) model disappears. next, utilizing the pantheon sample and 31 long gamma-ray bursts, we make a comparison among the different cosmographic expansions (z-redshift, y-redshift, e(y), log(1 + z), log(1 + z)+kij, and padé approximations) with the third-order and fourth-order expansions. the expansion order can significantly affect the results, especially for the y-redshift method. through analysis from the same sample, the lower-order expansion is preferable, except the y-redshift and e(y) methods. for the y-redshift and e(y) methods, despite adopting the same parameterization of y = z/(1 + z), the performance of the latter is better than that of the former. logarithmic polynomials, log(1 + z) and log(1 + z)+kij, perform significantly better than z-redshift, y-redshift, and e(y) methods, but worse than padé approximations. finally, we comprehensively analyze the results obtained from different samples. we find that the padé(2,1) method is suitable for both low and high redshift cases. the padé(2,2) method performs well in a high-redshift situation. for the y-redshift and e(y) methods, the only constraint on the first two parameters (q0 and j0) is reliable. | high-redshift cosmography: application and comparison with different methods |
bright quasars, observed when the universe was less than one billion years old (z > 5.5), are known to host massive black holes (∼109 m⊙) and are thought to reside in the center of massive dark matter overdensities. in this picture, overdensities of galaxies are expected around high-redshift quasars. however, observations based on the detection of lyman-break galaxies (lbgs) around these quasars do not offer a clear picture: this may be due to the uncertain redshift constraints of lbgs, which are solely selected through broadband filters. to circumvent such uncertainties, we here perform a search for lyman-alpha emitting galaxies (laes) in the field of the quasar pso j215.1512-16.0417 at z ∼ 5.73, through narrowband deep imaging with fors2 at the very large telescope. we study an area of 37 arcmin2, i.e., ∼206 comoving mpc2 at the redshift of the quasar. we find no evidence of an overdensity of laes in the quasar field with respect to blank-field studies. possible explanations for these findings may be that our survey volume is too small, or that the strong ionizing radiation from the quasar hinders galaxy formation in its immediate proximity. another possibility is that these quasars are not situated in the dense environments predicted by some simulations. | no overdensity of lyman-alpha emitting galaxies around a quasar at z ∼ 5.7 |
we present an atacama large millimeter/submillimeter array (alma) survey of co(4-3) line emitting galaxies in 17 quasar fields at z ~ 4 aimed at performing the first systematic search of dusty galaxies in high-z quasar environments. our blind search of galaxies around the quasars results in five co emitters with s/n ≥ 5.6 within a projected radius of r ≲ 1.5 h -1 cmpc and a velocity range of δv = ±1000 km s-1 around the quasar. in blank fields, we expect to detect only 0.28 co emitters within the same volume, implying a total overdensity of ${17.6}_{-7.6}^{+11.9}$ in our fields, and indicating that quasars trace massive structures in the early universe. we quantify this overdensity by measuring the small-scale clustering of co emitters around quasars, resulting in a cross-correlation length of ${r}_{0,\mathrm{qg}}={8.37}_{-2.04}^{+2.42}\,{h}^{-1}\,$ cmpc, assuming a fixed slope γ = 1.8. this contradicts the reported mild overdensities (x1.4) of lyα emitters (laes) in the same fields at scales of r ≲ 7 h -1 cmpc, which are well described by a cross-correlation length ${3.0}_{-1.4}^{+1.5}$ times lower than that measured for co emitters. we discuss some possibilities to explain this discrepancy, including low star formation efficiency, and excess of dust in galaxies around quasars. finally, we constrain, for the first time, the clustering of co emitters at z ~ 4, finding an autocorrelation length of r 0,co = 3.14 ±1.71 h -1 cmpc (with γ = 1.8). our work, together with the previous study of laes around quasars, traces simultaneously the clustering properties of both optical and dusty galaxy populations in quasars fields, stressing the importance of multiwavelength studies, and highlighting important questions about galaxy properties in high-z dense environments. | alma reveals a large overdensity and strong clustering of galaxies in quasar environments at z 4 |
which galaxies in the general population turn into active galactic nuclei (agns) is a keystone of galaxy formation and evolution. thanks to srg/erosita's contiguous 140 square degree pilot survey field, we constructed a large, complete, and unbiased soft x-ray flux-limited (fx > 6.5 × 10−15 erg s−1 cm−2) agn sample at low redshift, 0.05 < z < 0.55. two summary statistics, the clustering using spectra from sdss-v and galaxy-galaxy lensing with imaging from hsc, are measured and interpreted with halo occupation distribution and abundance matching models. both models successfully account for the observations. we obtain an exceptionally complete view of the agn halo occupation distribution. the population of agns is broadly distributed among halos with a mean mass of 3.9−2.4+2.0 × 1012 m⊙. this corresponds to a large-scale halo bias of b(z = 0.34) = 0.99−0.10+0.08. the central occupation has a large transition parameter, σlog10(m) = 1.28 ± 0.2. the satellite occupation distribution is characterized by a shallow slope, αsat = 0.73 ± 0.38. we find that agns in satellites are rare, with fsat < 20%. most soft x-ray-selected agns are hosted by central galaxies in their dark matter halo. a weak correlation between soft x-ray luminosity and large-scale halo bias is confirmed (3.3σ). we discuss the implications of environmental-dependent agn triggering. this study paves the way toward fully charting, in the coming decade, the coevolution of x-ray agns, their host galaxies, and dark matter halos by combining erosita with sdss-v, 4most, desi, lsst, and euclid data. | the cosmic web of x-ray active galactic nuclei seen through the erosita final equatorial depth survey (efeds) |
gas surrounding high-redshift galaxies has been studied through observations of absorption line systems toward background quasars for decades. however, it has proven difficult to identify and characterize the galaxies associated with these absorbers due to the intrinsic faintness of the galaxies compared with the quasars at optical wavelengths. using the atacama large millimeter/submillimeter array, we report on detections of [c ii] 158-μm line and dust-continuum emission from two galaxies associated with two such absorbers at a redshift of z ~ 4. our results indicate that the hosts of these high-metallicity absorbers have physical properties similar to massive star-forming galaxies and are embedded in enriched neutral hydrogen gas reservoirs that extend well beyond the star-forming interstellar medium of these galaxies. | [c ii] 158-μm emission from the host galaxies of damped lyman-alpha systems |
the first black hole seeds, formed when the universe was younger than ∼500 myr, are recognized to play an important role for the growth of early (z ∼ 7) supermassive black holes. while progresses have been made in understanding their formation and growth, their observational signatures remain largely unexplored. as a result, no detection of such sources has been confirmed so far. supported by numerical simulations, we present a novel photometric method to identify black hole seed candidates in deep multiwavelength surveys. we predict that these highly obscured sources are characterized by a steep spectrum in the infrared (1.6-4.5 μm), i.e. by very red colours. the method selects the only two objects with a robust x-ray detection found in the candels/goods-s survey with a photometric redshift z ≳ 6. fitting their infrared spectra only with a stellar component would require unrealistic star formation rates (≳2000 m⊙ yr-1). to date, the selected objects represent the most promising black hole seed candidates, possibly formed via the direct collapse black hole scenario, with predicted mass >105 m⊙. while this result is based on the best photometric observations of high-z sources available to date, additional progress is expected from spectroscopic and deeper x-ray data. upcoming observatories, like the jwst, will greatly expand the scope of this work. | first identification of direct collapse black hole candidates in the early universe in candels/goods-s |
we have applied a convolutional neural network (cnn) to classify and detect quasars in the sloan digital sky survey stripe 82 and also to predict the photometric redshifts of quasars. the network takes the variability of objects into account by converting light curves into images. the width of the images, noted w, corresponds to the five magnitudes ugriz and the height of the images, noted h, represents the date of the observation. the cnn provides good results since its precision is 0.988 for a recall of 0.90, compared to a precision of 0.985 for the same recall with a random forest classifier. moreover 175 new quasar candidates are found with the cnn considering a fixed recall of 0.97. the combination of probabilities given by the cnn and the random forest makes good performance even better with a precision of 0.99 for a recall of 0.90. for the redshift predictions, the cnn presents excellent results which are higher than those obtained with a feature extraction step and different classifiers (a k-nearest-neighbors, a support vector machine, a random forest and a gaussian process classifier). indeed, the accuracy of the cnn within |δz| < 0.1 can reach 78.09%, within |δz| < 0.2 reaches 86.15%, within |δz| < 0.3 reaches 91.2% and the value of root mean square (rms) is 0.359. the performance of the knn decreases for the three |δz| regions, since within the accuracy of |δz| < 0.1, |δz| < 0.2, and |δz| < 0.3 is 73.72%, 82.46%, and 90.09% respectively, and the value of rms amounts to 0.395. so the cnn successfully reduces the dispersion and the catastrophic redshifts of quasars. this new method is very promising for the future of big databases such as the large synoptic survey telescope. a table of the candidates is only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/611/a97 | deep learning approach for classifying, detecting and predicting photometric redshifts of quasars in the sloan digital sky survey stripe 82 |
the lyman-α (hereafter lyα) forest is a probe of large-scale matter density fluctuations at high redshift, z > 2.1. it consists of h i absorption spectra along individual lines-of-sight. if the line-of-sight density is large enough, 3d maps of h i absorption can be inferred by tomographic reconstruction. in this article, we investigate the lyα forest available in the stripe 82 field (220 deg2), based on the quasar spectra from sdss data release dr16. the density of observed quasar spectra is 37 deg-2 with a mean pixel signal-to-noise ratio of two per angstrom. this study provides an intermediate case between the average sdss density and that of the much denser but smaller clamato survey. we derive a 3d map of large-scale matter fluctuations from these data, using a wiener filter technique. the total volume of the map is 0.94 h-3 gpc3. its resolution is 13 h-1 mpc, which is related to the mean transverse distance between nearest lines-of-sight. from this map, we provide a catalog of voids and protocluster candidates in the cosmic web. the map-making and void catalog are compared to simulated eboss stripe 82 observations. a stack over quasar positions provides a visualization of the lyα forest-quasar cross-correlation. this tomographic reconstruction constitutes the largest-volume high-redshift 3d map of matter fluctuations. | a tomographic map of the large-scale matter distribution using the eboss—stripe 82 lyα forest |
we investigate the astrophysics of radio-emitting star-forming galaxies and active galactic nuclei (agns) and elucidate their statistical properties in the radio band, including luminosity functions, redshift distributions, and number counts at sub-mjy flux levels, which will be crucially probed by next-generation radio continuum surveys. specifically, we exploit the model-independent approach by mancuso et al. to compute the star formation rate functions, the agn duty cycles, and the conditional probability of a star-forming galaxy to host an agn with given bolometric luminosity. coupling these ingredients with the radio emission properties associated with star formation and nuclear activity, we compute relevant statistics at different radio frequencies and disentangle the relative contribution of star-forming galaxies and agns in different radio luminosity, radio flux, and redshift ranges. finally, we highlight that radio-emitting star-forming galaxies and agns are expected to host supermassive black holes accreting with different eddington ratio distributions and to occupy different loci in the galaxy main-sequence diagrams. these specific predictions are consistent with current data sets but need to be tested with larger statistics via future radio data with multiband coverage on wide areas, as will become routinely achievable with the advent of the square kilometre array and its precursors. | galaxy evolution in the radio band: the role of star-forming galaxies and active galactic nuclei |
we present the largest, publicly available sample of damped lyα systems (dlas) along the lines of sight of swift-discovered gamma-ray bursts (grbs) in order to investigate the environmental properties of long grb hosts in the z = 1.8-6 redshift range. compared with the most recent quasar dla sample (qso-dla), our analysis shows that grb-dlas probe a more metal-enriched environment at z≳ 3, up to [x/h]∼ -0.5. in the z = 2-3 redshift range, despite the large number of lower limits, there are hints that the two populations may be more similar (only at a 90% significance level) than at higher redshifts. also, at high-z, the grb-dla average metallicity seems to decline at a lower rate than the qso-dlas: grb-dla hosts may be polluted with metals at least as far as ∼ 2 kpc from the grb explosion site, probably due to previous star formation episodes and/or supernova explosions. this shallow metallicity trend, now extended up to z∼ 5, confirms previous results that grb hosts are star-forming and have, on average, higher metallicities than the general qso-dla population. finally, our host metallicity measurements are broadly consistent with the predictions derived from the hypothesis of two channels of grb progenitors, one of which is mildly affected by a metallicity bias, although more data are needed to constrain the models at z≳ 4. | unveiling the secrets of metallicity and massive star formation using dlas along gamma-ray bursts |
accurate and precise measurements of the hubble constant are critical for testing our current standard cosmological model and revealing possibly new physics. with hubble space telescope (hst) imaging, each strong gravitational lens system with measured time delays can allow one to determine the hubble constant with an uncertainty of ∼7 per cent. since hst will not last forever, we explore adaptive-optics (ao) imaging as an alternative that can provide higher angular resolution than hst imaging but has a less stable point spread function (psf) due to atmospheric distortion. to make ao imaging useful for time-delay-lens cosmography, we develop a method to extract the unknown psf directly from the imaging of strongly lensed quasars. in a blind test with two mock data sets created with different psfs, we are able to recover the important cosmological parameters (time-delay distance, external shear, lens-mass profile slope, and total einstein radius). our analysis of the keck ao image of the strong lens system rxj 1131-1231 shows that the important parameters for cosmography agree with those based on hst imaging and modelling within 1σ uncertainties. most importantly, the constraint on the model time-delay distance by using ao imaging with 0.09 arcsec resolution is tighter by ∼50 per cent than the constraint of time-delay distance by using hst imaging with 0.09 arcsec when a power-law mass distribution for the lens system is adopted. our psf reconstruction technique is generic and applicable to data sets that have multiple nearby point sources, enabling scientific studies that require high-precision models of the psf. | sharp - iii. first use of adaptive-optics imaging to constrain cosmology with gravitational lens time delays |
we have conducted a search for z ≃ 7 lyman-break galaxies over 8.2 deg2 of near-infrared imaging from the visible and infrared survey telescope for astronomy (vista) deep extragalactic observations (video) survey in the xmm-newton-large scale structure (xmm-lss) and the extended chandra deep field-south (ecdf-s) fields. candidate galaxies were selected from a full photometric redshift analysis down to a y + j depth of 25.3 (5σ), utilizing deep auxiliary optical and spitzer/infrared array camera (irac) data to remove brown dwarf and red interloper galaxy contaminants. our final sample consists of 28 candidate galaxies at 6.5 ≤ z ≤ 7.5 with -23.5 ≤ muv ≤ -21.6. we derive stellar masses of 9.1 ≤ log10(m⋆/m⊙) ≤ 10.9 for the sample, suggesting that these candidates represent some of the most massive galaxies known at this epoch. we measure the rest-frame ultraviolet (uv) luminosity function (lf) at z ≃ 7, confirming previous findings of a gradual decline in number density at the bright end (muv < -22) that is well described by a double power law (dpl). we show that quasar contamination in this magnitude range is expected to be minimal, in contrast to conclusions from recent pure-parallel hubble studies. our results are up to a factor of 10 lower than previous determinations from optical-only ground-based studies at muv ≲ -23. we find that the inclusion of yjhks photometry is vital for removing brown dwarf contaminants, and z ≃ 7 samples based on red optical data alone could be highly contaminated (≳50 per cent). in comparison with other robust z > 5 samples, our results further support little evolution in the very bright end of the rest-frame uv lf from z = 5-10, potentially signalling a lack of mass quenching and/or dust obscuration in the most massive galaxies in the first gyr. | the bright end of the galaxy luminosity function at z ≃ 7 from the vista video survey |
we study the evolution of galaxies and the circumgalactic medium (cgm) through cosmic time by correlating ∼50,000 mg ii absorbers, tracers of cool gas (∼104 k), detected in the sloan digital sky survey quasar spectra with galaxies detected in the desi legacy imaging surveys. by doing so, we extract the properties of galaxies associated with absorbers from redshift 0.4 to 1.3 with effectively ∼15,000 pairs and explore the covering fraction of mg ii absorbers as a function of galaxy type, stellar mass, impact parameter, and redshift. we find that the gas covering fraction increases with stellar mass of galaxies by $\sim {m}_{* }^{0.4}$ . however, after we normalize the impact parameter by the virial radius of dark matter halos, the gas profiles around galaxies with masses ranging from 109 to ${10}^{11}\,{m}_{\odot }$ become weakly dependent on stellar mass. in addition, the gas distribution depends on galaxy type: the covering fraction within $0.3\,{r}_{\mathrm{vir}}$ around star-forming galaxies is 2-4 times higher than that around passive galaxies at all redshifts. we find that the covering fraction of strong absorbers ( ${w}_{\lambda 2796}\gt 1\,\mathring{\rm a} $ ) around both types of galaxies evolves significantly with redshift, similarly to the evolution of star formation rate (sfr) of galaxies, while such an evolution is not detected for weak absorbers ( ${w}_{\lambda 2796}\lt 1\,\mathring{\rm a} $ ). we quantify the h i mass traced by strong absorbers and find that the gas mass around galaxies evolves consistently with the sfr of galaxies. this result suggests that the properties of galaxies and their cgm coevolve through cosmic time. finally, we discuss the origins of strong absorbers around passive galaxies and argue that its redshift evolution may trace the star formation activity of satellite galaxies. | the coevolution of galaxies and the cool circumgalactic medium probed with the sdss and desi legacy imaging surveys |
we describe the polami (polarimetric monitoring of agn at millimetre wavelengths) programme for the monitoring of all four stokes parameters of a sample of bright radio-loud active galactic nuclei with the iram 30-m telescope at 3.5 and 1.3 mm. the programme started in 2006 october and accumulated, until 2014 august, 2300 observations at 3.5 mm, achieving a median time sampling interval of 22 d for the sample of 37 sources. this first paper explains the source selection, mostly blazars, the observing strategy and data calibration and gives the details of the instrumental polarization corrections. the sensitivity (1σ) reached at 3.5 mm is 0.5 per cent (linear polarization degree), 4.7° (polarization angle), and 0.23 per cent (circular polarization), while the corresponding values at 1.3 mm are 1.7 per cent, 9.9° and 0.72 per cent, respectively. the data quality is demonstrated by the time sequences of our calibrators mars and uranus. for the quasar 3c 286, widely used as a linear polarization calibrator, we give improved estimates of its linear polarization, and show for the first time occasional detections of its weak circular polarization, which suggests a small level of variability of the source at millimeter wavelengths. | polami: polarimetric monitoring of agn at millimetre wavelengths - i. the programme, calibration and calibrator data products |
we constrain the h i photoionization rate (γ _{h i}) at z ≲ 0.45 by comparing the flux probability distribution function and power spectrum of the lyα forest data along 82 quasi-stellar object (qso) sightlines obtained using cosmic origins spectrograph with models generated from smoothed particle hydrodynamic simulations. we have developed a module named 'code for ionization and temperature evolution (cite)' for calculating the intergalactic medium (igm) temperature evolution from high to low redshifts by post-processing the gadget-2 simulation outputs. our method, that produces results consistent with other simulations, is computationally less expensive thus allowing us to explore a large parameter space. it also allows rigorous estimation of the error covariance matrix for various statistical quantities of interest. we find that the best-fitting γ _{h i}(z) increases with z and follows (4 ± 0.1) × 10-14 (1 + z)4.99 ± 0.12 s-1. at any given z, the typical uncertainties δ γ _{h i} / γ _{h i} are ∼25 per cent that contains not only the statistical errors but also those arising from possible degeneracy with the thermal history of the igm and cosmological parameters and uncertainties in fitting the qso continuum. these values of γ _{h i} favour the scenario where only qsos contribute to the ionizing background at z < 2. our derived 3σ upper limit on average escape fraction is 0.008, consistent with measurements of low-z galaxies. | intergalactic lyman continuum photon budget in the past 5 billion years |
we present results from a survey of galaxies in the fields of six z ≥ 3 damped lyman α (lyα) systems (dlas) using the multi unit spectroscopic explorer (muse) at the very large telescope (vlt). we report a high detection rate of up to {≈ } 80{{ per cent}} of galaxies within 1000 km s-1 from dlas and with impact parameters between 25 and 280 kpc. in particular, we discovered five high-confidence lyα emitters associated with three dlas, plus up to nine additional detections across five of the six fields. the majority of the detections are at relatively large impact parameters (>50 kpc) with two detections being plausible host galaxies. among our detections, we report four galaxies associated with the most metal-poor dla in our sample (z/z⊙ = -2.33 ± 0.22), which trace an overdense structure resembling a filament. by comparing our detections with predictions from the evolution and assembly of galaxies and their environments (eagle) cosmological simulations and a semi-analytic model designed to reproduce the observed bias of dlas at z > 2, we conclude that our observations are consistent with a scenario in which a significant fraction of dlas trace the neutral regions within haloes with a characteristic mass of m_h ≈ 10^{11}-10^{12} m_\odot, in agreement with the inference made from the large-scale clustering of dlas. we finally show how larger surveys targeting ≈25 absorbers have the potential of constraining the characteristic masses of haloes hosting high-redshift dlas with sufficient accuracy to discriminate between different models. | linking gas and galaxies at high redshift: muse surveys the environments of six damped lyα systems at z ≈ 3 |
we assemble a catalogue of 488 spectroscopically confirmed very high (z ≥ 5.00) redshift quasars (vhzq) and report their near- (zyjhks/k) and mid- (wise w1234) infrared properties. 97 per cent of the vhzq sample is detected in one or more near-infrared (nir) band, with lack of coverage rather than lack of depth being the reason for the non-detections. 389 (80 per cent) of the very high redshift quasars are detected at 3.4 μm in the w1 band from the unwise catalogue and all of the z ≥ 7 quasars are detected in both unwise w1 and w2. using archival wide field camera (wfcam)/united kingdom infrared telescope (ukirt) and vista infrared camera (vircam)/visible and infrared survey telescope for astronomy (vista) data we check for photometric variability that might be expected from super-eddington accretion. we find 28 of the quasars have sufficient nir measurements and signal-to-noise ratio to look for variability. weak variability was detected in multiple bands of sloan digital sky survey (sdss) j0959+0227, and very marginally in the y-band of mmt j0215-0529. only one quasar, sdss j0349+0034, shows significant differences between wfcam and vista magnitudes in one band. with supermassive black hole accretion likely to be redshift invariant up to very high redshift, further monitoring of these sources is warranted. all the data, analysis codes and plots used and generated here can be found at: github.com/d80b2t/vhzq. | the near and mid-infrared photometric properties of known redshift z ≥ 5 quasars |
we evaluate the impact of imaging systematics on the clustering of luminous red galaxies (lrg), emission-line galaxies (elg), and quasars (qso) targeted for the upcoming dark energy spectroscopic instrument (desi) survey. using data release 7 of the decam legacy survey, we study the effects of astrophysical foregrounds, stellar contamination, differences between north galactic cap and south galactic cap measurements, and variations in imaging depth, stellar density, galactic extinction, seeing, airmass, sky brightness, and exposure time before presenting survey masks and weights to mitigate these effects. with our sanitized samples in hand, we conduct a preliminary analysis of the clustering amplitude and evolution of the desi main targets. from measurements of the angular correlation functions, we determine power law fits $r_0 = 7.78 \pm 0.26\, h^{-1}$ mpc, γ = 1.98 ± 0.02 for lrgs and $r_0 = 5.45 \pm 0.1\, h^{-1}$ mpc, γ = 1.54 ± 0.01 for elgs. additionally, from the angular power spectra, we measure the linear biases and model the scale-dependent biases in the weakly non-linear regime. both sets of clustering measurements show good agreement with survey requirements for lrgs and elgs, attesting that these samples will enable desi to achieve precise cosmological constraints. we also present clustering as a function of magnitude, use cross-correlations with external spectroscopy to infer dn/dz and measure clustering as a function of luminosity, and probe higher order clustering statistics through counts-in-cells moments. | imaging systematics and clustering of desi main targets |
in the present paper, we treat the problem of the existence of quark stars (qss) for selected homogeneous and unpaired charge-neutral 3-flavor interacting quark matter with o (ms4) corrections equations of state (eos). using the eos combined with the tolmann-oppenheimer-volkoff (tov) structure equations, the properties of stars are explored by obtaining their mass-radius relations. all calculations are carried out within the framework of the r-squared gravity defined by f (r) = r + ar2. our main goal is to discuss the effect for a wide range of the r-squared gravity parameter, a, on the mass-radius and the mass-central mass density (m -ϵc) relation of qss. furthermore, we investigate the dynamical stability condition for those stars, and we show that their dynamical stability depends on the anisotropic parameters b⊥ and a4⊥ coming from the respective eos. in such a scenario our results provide circumstantial evidence in favor of super-massive pulsars. | anisotropic quark stars in r2 gravity |
recent searches for the hosts of z ~ 4 damped ly α absorbers (dlas) have detected bright galaxies at distances of tens of kpc from the dla. using the fire-2 cosmological zoom simulations, we argue that these relatively large distances are due to a predominantly cool and neutral inner circumgalactic medium (cgm) surrounding high-redshift galaxies. the inner cgm is cool because of the short cooling time of hot gas in ${\lesssim}10^{12}\, {\rm m_{\odot }}$ haloes, which implies that accretion and feedback energy are radiated quickly, while it is neutral due to high volume densities and column densities at high redshift that shield cool gas from photoionization. our analysis predicts large dla covering factors (${\gtrsim}50{{\ \rm per\ cent}}$) out to impact parameters ~0.3[(1 + z)/5]3/2rvir from the central galaxies at z ≳ 1, equivalent to a proper distance of ${\sim}21\, m_{12}^{1/3} \left(\left(1+z\right)/5\right)^{1/2}\, {\rm kpc}$ (rvir and m12 are the halo virial radius and mass in units of $10^{12}\, {\rm m_{\odot }}$, respectively). this implies that dla covering factors at z ~ 4 may be comparable to unity out to a distance ~10 times larger than stellar half-mass radii. a predominantly neutral inner cgm in the early universe suggests that its mass and metallicity can be directly constrained by absorption surveys, without resorting to the large ionization corrections as required for ionized cgm. | neutral cgm as damped ly α absorbers at high redshift |
we evaluate the cosmological coalescence and detection rates for massive black hole (mbh) binaries targeted by the gravitational wave observatory laser interferometer space antenna (lisa). our calculation starts with a population of gravitationally unbound mbh pairs, drawn from the tng50-3 cosmological simulation, and follows their orbital evolution from kiloparsec scales all the way to coalescence using a semi-analytic model developed in our previous work. we find that for the majority of mbh pairs that coalesce within a hubble time dynamical friction is the most important mechanism that determines their coalescence rate. our model predicts an mbh coalescence rate ≲0.45 yr-1 and a lisa detection rate ≲0.34 yr-1. most lisa detections should originate from 106 to 106.8 m ⊙ mbhs in gas-rich galaxies at redshifts 1.6 ≤ z ≤ 2.4 and have a characteristic signal-to-noise ratio s/n ~100. we however find a dramatic reduction in the coalescence and detection rates, as well as the average s/n, if the effects of radiative feedback from accreting mbhs are taken into account. in this case, the mbh coalescence rate is reduced by 78% (to ≲0.1 yr-1), and the lisa detection rate is reduced by 94% (to 0.02 yr-1), whereas the average s/n is ~10. we emphasize that our model provides a conservative estimate of the lisa detection rates, due to the limited mbh mass range in tng50-3, consistent with other works in the literature that draw their mbh pairs from cosmological simulations. | massive black hole binaries from the tng50-3 simulation. i. coalescence and lisa detection rates |
we investigate the star-forming main sequence of the host galaxies of a large, well-defined sample of 453 redshift ~0.3 quasars with previously available star formation rates by deriving stellar masses from modeling their broadband (grizy) spectral energy distribution. we perform two-dimensional, simultaneous, multi-filter decomposition of pan-starrs1 3π steradian survey images to disentangle the active galactic nucleus (agn) from its host galaxy, by explicitly considering, for the first time, the wavelength variation of galaxy structures. we quantify the sérsic profiles and sizes of the host galaxies from mock agns generated from both real and idealized galaxies. detailed morphological classifications of the calibration galaxy sample using hubble space telescope images enable us to estimate crude morphological types of the quasars. although the majority (~60%) of the quasars are hosted by bulge-dominated, early-type galaxies, a substantial fraction (~40%) reside in disk-dominated, late-type galaxies, suggesting that at least in these systems major mergers have not played a significant role in regulating their agn activity, in agreement with recent simulations and observations of nearby quasars. the vast majority (~90%) of the quasars have star formation rates that place them on or above the galaxy star-forming main sequence, with more rapidly accreting agns displaced further above the main sequence. quasar host galaxies generally follow the stellar mass-size relation defined by inactive galaxies, both for late-type and early-type systems, but roughly 1/3 of the population has smaller sizes at a given stellar mass, reminiscent of compact star-forming galaxies at higher redshift. | the star-forming main sequence of the host galaxies of low-redshift quasars |
the science operations of the spacecraft and remote sensing instruments for the martian moon exploration (mmx) mission are discussed by the mission operation working team. in this paper, we describe the phobos observations during the first 1.5 years of the spacecraft's stay around mars, and the deimos observations before leaving the martian system. in the phobos observation, the spacecraft will be placed in low-altitude quasi-satellite orbits on the equatorial plane of phobos and will make high-resolution topographic and spectroscopic observations of the phobos surface from five different altitudes orbits. the spacecraft will also attempt to observe polar regions of phobos from a three-dimensional quasi-satellite orbit moving out of the equatorial plane of phobos. from these observations, we will constrain the origin of phobos and deimos and select places for landing site candidates for sample collection. for the deimos observations, the spacecraft will be injected into two resonant orbits and will perform many flybys to observe the surface of deimos over as large an area as possible. | science operation plan of phobos and deimos from the mmx spacecraft |
large o vi columns are observed around star-forming low-redshift ∼ {l}*galaxies, with a dependence on impact parameter indicating that most {{{o}}}5+ particles reside beyond half the halo virial radius (≳ 100 {kpc}). in order to constrain the nature of the gas traced by {{o}} {{vi}}, we analyze additional observables of the outer halo, namely {{h}} {{i}} to o vi column ratios of 1-10, an absence of low-ion absorption, a mean differential extinction of {e}b-v≈ {10}-3, and a linear relation between the o vi column and the o vi velocity width. we contrast these observations with two physical scenarios: (1) o vi traces high-pressure (∼ 30 {cm}}-3 {{k}}) collisionally ionized gas cooling from a virially shocked phase, and (2) o vi traces low-pressure (≲ 1 {cm}}-3 {{k}}) gas beyond the accretion shock, where the gas is in ionization and thermal equilibrium with the uv background. we demonstrate that the high-pressure scenario requires multiple gas phases to explain the observations and a large deposition of energy at ≳ 100 {kpc} to offset the energy radiated by the cooling gas. in contrast, the low-pressure scenario can explain all considered observations with a single gas phase in thermal equilibrium, provided that the baryon overdensity is comparable to the dark-matter overdensity and that the gas is enriched to ≳ {z}⊙ /3 with an ism-like dust-to-metal ratio. the low-pressure scenario implies that o vi traces a cool flow with a mass flow rate of ∼ 5 {{{m}}}⊙{yr}}-1, comparable to the star formation rate of the central galaxies. the o vi line widths are consistent with the velocity shear expected within this flow. the low-pressure scenario predicts a bimodality in absorption line ratios at ∼ 100 {kpc}, due to the pressure jump across the accretion shock. | does circumgalactic o vi trace low-pressure gas beyond the accretion shock? clues from h i and low-ion absorption, line kinematics, and dust extinction |
we report on the spectroscopic confirmation of a large-scale structure around the luminous z = 6.31 quasi-stellar object (qso) sdss j1030+0524, powered by a one billion solar mass black hole. the structure is populated by at least six members, namely, four lyman-break galaxies (lbgs), and two lyman alpha emitters (laes). the four lbgs were identified among a sample of 21 i-band dropouts with zab < 25.5 selected up to projected separations of 5 physical mpc (15 arcmin) from the qso. their redshifts were determined through multi-object spectroscopic observations at 8-10 m class telescopes lasting up to eight hours. the two laes were identified in a 6 h vlt/muse observation centered on the qso. the redshifts of the six galaxies cover the range between 6.129-6.355. assuming that the peculiar velocities are negligible, this range corresponds to radial separations of ±5 physical mpc from the qso, that is comparable to the projected scale of the observed lbg distribution on the sky. we conservatively estimate that this structure is significant at a level > 3.5σ and that the level of the galaxy overdensity is at least 1.5-2 within the large volume sampled (∼780 physical mpc3). the spectral properties of the six member galaxies (lyα strength and uv luminosity) are similar to those of field galaxies at similar redshifts. this is the first spectroscopic identification of a galaxy overdensity around a supermassive black hole in the first billion years of the universe. our finding lends support to the idea that the most distant and massive black holes form and grow within massive (>1012 m⊙) dark matter halos in large-scale structures and that the absence of earlier detections of such systems is likely due to observational limitations. | web of the giant: spectroscopic confirmation of a large-scale structure around the z = 6.31 quasar sdss j1030+0524 |
the most luminous quasars at z > 6 are suspected to be both highly clustered and to reside in the most massive dark matter halos in the early universe, making them prime targets to search for galaxy overdensities and/or protoclusters. we search for lyman-break dropout-selected galaxies using hst wfc3/acs broadband imaging in the fields of three 6 < z < 7 quasars, as well as for their simultaneously observed coordinated parallel fields, and constrain their photometric redshifts using eazy. one field, j0305-3150, shows a volume density 10× higher than the blank-field uv luminosity function (uvlf) at m uv < -20, with tentative evidence of a 3σ overdensity in its parallel field located 15 cmpc away. another field, j2054-0005, shows an angular overdensity within 500 ckpc from the quasar, but this is still consistent with uvlf predictions within 3σ, while the last field, j2348-3054, shows no enhancement. we discuss methods for reducing uncertainty in overdensity measurements when using photometric selection and show that we can robustly select lyman-break galaxies (lbgs) consistent with being physically associated with the quasar, corroborated by existing jwst/nircam wfss data in the j0305 field. even accounting for incompleteness, the overdensities in j0305 and j2054 are higher for brighter galaxies at short angular separations, suggesting preferential enhancement of more massive galaxies in the quasar's immediate vicinity. finally, we compare the population of lbgs with previously identified [c ii] and millimeter-continuum companions. the lbg overdensities are not accompanied by an enhanced number of dusty galaxies, suggesting that the overdense quasar fields are not in the bursty star-forming phase sometimes seen in high-redshift protoclusters. | a mixture of lbg overdensities in the fields of three 6 < z < 7 quasars: implications for the robustness of photometric selection |
we investigate whether the dust content of the circum-galactic medium (cgm) depends on the location of the quasar sightline with respect to the galaxy major-axis using 13 galaxy-mg ii absorber pairs (9-81 kpc distance) from the muse gas flow and wind (megaflow) survey at 0.4 < z < 1.4. the dust content of the cgm is obtained from [zn/fe] using ultraviolet and visual echelle spectrograph data. when a direct measurement of [zn/fe] is unavailable, we estimate the dust depletion from a method that consists in solving for the depletion from multiple singly ionized ions (e.g. mn ii, cr ii, and zn ii) since each ion depletes on dust grains at different rates. we find a positive correlation between the azimuthal angle and [zn/fe] with a pearson's r = 0.70 ± 0.14. the sightlines along the major axis show [zn/fe] < 0.5, whereas the [zn/fe] is > 0.8 along the minor axis. these results suggest that the cgm along the minor axis is on average more metal enriched (by ≈ 1 dex) than the gas located along the major axis of galaxies provided that dust depletion is a proxy for metallicity. this anisotropic distribution is consistent with recent results on outflow and accretion in hydro-dynamical simulations. | muse gas flow and wind v. the dust/metallicity-anisotropy of the circum-galactic medium |
the amplitude of the ionizing background that pervades the intergalactic medium (igm) at the end of the epoch of reionization provides a valuable constraint on the emissivity of the sources that reionized the universe. while measurements of the ionizing background at lower redshifts rely on a simulation-calibrated mapping between the photoionization rate and the mean transmission of the lyα forest, at z ≳ 6 the igm becomes increasingly opaque and transmission arises solely in narrow spikes separated by saturated gunn-peterson troughs. in this regime, the traditional approach of measuring the average transmission over large ∼50 mpc/h regions is less sensitive and suboptimal. in addition, the five times smaller oscillator strength of the lyβ transition implies that the lyβ forest is considerably more transparent at z ≳ 6, even in the presence of contamination by foreground z ∼ 5 lyα forest absorption. in this work we present a novel statistical approach to analyze the joint distribution of transmission spikes in the cospatial z ∼ 6 lyα and lyβ forests. our method relies on approximate bayesian computation (abc), which circumvents the necessity of computing the intractable likelihood function describing the highly correlated lyα and lyβ transmission. we apply abc to mock data generated from a large-volume hydrodynamical simulation combined with a state-of-the-art model of ionizing background fluctuations in the post-reionization igm and show that it is sensitive to higher igm neutral hydrogen fractions than previous techniques. as a proof of concept, we apply this methodology to a real spectrum of a z = 6.54 quasar and measure the ionizing background from 5.4 ≤ z ≤ 6.4 along this sightline with ∼0.2 dex statistical uncertainties. some of the data presented herein were obtained at the w. m. keck observatory, which is operated as a scientific partnership among the california institute of technology, the university of california, and the national aeronautics and space administration. the observatory was made possible by the generous financial support of the w. m. keck foundation. | a new method to measure the post-reionization ionizing background from the joint distribution of lyα and lyβ forest transmission |
the recent discovery of supermassive black holes (smbhs) in high mass ultra-compact dwarf galaxies (ucds) suggests that at least some ucds are the nuclear star clusters of stripped galaxies. in this paper we present a new method to estimate how many ucds host an smbh and thus are stripped galaxy nuclei. we revisit the dynamical mass measurements that suggest many ucds have more mass than expected from stellar population estimates, which observations have shown is due to the presence of an smbh. we revise the stellar population mass estimates using a new empirical relation between the mass-to-light ratio (m/l) and metallicity to predict which ucds most likely host an smbh. we calculate the fraction of ucds that host smbhs across their entire luminosity range for the first time. we then apply the smbh occupation fraction to the observed luminosity function of ucds and estimate that in the fornax and virgo clusters alone there should be {69}-25+32 stripped nuclei with smbhs. this analysis shows that stripped nuclei are almost as common in clusters as present-day galaxy nuclei. we estimate the smbh number density caused by stripped nuclei to be (2-8) × 10-3 mpc-3, which represents a significant fraction (8%-32%) of the smbh density in the local universe. these smbhs hidden in stripped nuclei increase expected event rates for tidal disruption events and smbh-smbh and smbh-bh mergers. the existence of numerous stripped nuclei with smbhs are a direct consequence of hierarchical galaxy formation, but until now their impact on the smbh density had not been quantified. | the impact of stripped nuclei on the supermassive black hole number density in the local universe |
similarly to the cosmic star formation history, the black hole accretion rate density of the universe peaked at 1 < z < 3. this cosmic epoch is hence best suited for investigating the effects of radiative feedback from active galactic nucleus (agn). observational efforts are under way to quantify the impact of the agn feedback, if any, on their host galaxies. here, we present a study of the molecular gas content of agn hosts at z ∼ 1.5 using co[2-1] line emission observed with atacama large millimeter/sub-mm array (alma) for a sample of 10 agns. we compare this with a sample of galaxies without an agn matched in redshift, stellar mass and star formation rate. we detect co in three agns with lco ∼ 6.3-25.1 × 109 l⊙, which translates to a molecular hydrogen gas mass of 2.5-10 × 1010 m⊙ assuming conventional conversion factor of αco ∼ 3.6. our results indicate a >99 per cent probability of lower depletion time-scales and lower molecular gas fractions in agn hosts with respect to the non-agn comparison sample. we discuss the implications of these observations on the impact that agn feedback may have on star formation efficiency of z >1 galaxies. | alma observations of cold molecular gas in agn hosts at z ∼ 1.5 - evidence of agn feedback? |
we present x-ray and multiwavelength analyses of 32 weak emission-line quasars (wlqs) selected in a consistent and unbiased manner. new chandra 3.1-4.8 ks observations were obtained for 14 of these wlqs with c iv rest-frame equivalent widths (rews) of 5-15 å, and these serve as an x-ray observational "bridge" between previously studied wlqs with c iv rew ≲ 5 å and more-typical quasars with c iv rew ≈ 15-100 å. we have identified and quantified a strong dependence of the fraction of x-ray weak quasars upon c iv rew; this fraction declines by a factor of ≈ 13 (from ≈ 44% to ≈ 3%) for c iv rew ranging from 4 to 50 å, and the rate of decline appears particularly strong in the 10-20 å range. the dependence broadly supports the proposed "shielding" model for wlqs, in which a geometrically and optically thick inner accretion disk, expected for a quasar accreting at a high eddington ratio, both prevents ionizing euv/x-ray photons from reaching the high-ionization broad emission-line region and also sometimes blocks the line of sight to the central x-ray-emitting region. this model is also supported by the hard average spectral shape of x-ray weak wlqs (with a power-law effective photon index of γ _eff=1.19^{+0.56}_{-0.45}). additionally, we have examined ultraviolet (uv) continuum/emission-line properties that might trace x-ray weakness among wlqs, confirming that red uv continuum color is the most-effective tracer. | connecting the x-ray properties of weak-line and typical quasars: testing for a geometrically thick accretion disk |
in this paper we analyze the kinematics, chemistry, and physical properties of a sample of the most metal-poor damped lyα systems (dlas), to uncover their links to modern-day galaxies. we present evidence that the dla population as a whole exhibits a "knee" in the relative abundances of the α-capture and fe-peak elements when the metallicity is [fe/h] sime -2.0, assuming that zn traces the buildup of fe-peak elements. in this respect, the chemical evolution of dlas is clearly different from that experienced by milky way halo stars, but resembles that of dwarf spheroidal galaxies in the local group. we also find a close correspondence between the kinematics of local group dwarf galaxies and of high-redshift metal-poor dlas, which further strengthens this connection. on the basis of such similarities, we propose that the most metal-poor dlas provide us with a unique opportunity to directly study the dwarf galaxy population more than ten billion years in the past, at a time when many dwarf galaxies were forming the bulk of their stars. to this end, we have measured some of the key physical properties of the dla gas, including their neutral gas mass, size, kinetic temperature, density, and turbulence. we find that metal-poor dlas contain a warm neutral medium with t gas ~= 9600 k predominantly held up by thermal pressure. furthermore, all of the dlas in our sample exhibit a subsonic turbulent mach number, implying that the gas distribution is largely smooth. these results are among the first empirical descriptions of the environments where the first few generations of stars may have formed in the universe. based on observations collected at the european organisation for astronomical research in the southern hemisphere, chile (vlt program ids: 60.a-9022(a), 65.o-0063(b), 65.o-0296(a), 67.a-0022(a), 67.a-0078(a), 68.a-0600(a), 68.b-0115(a), 70.a-0425(c), 078.a-0185(a), 080.a-0014(a), 082.a-0544(a), 083.a-0042(a), 083.a-0454(a), 085.a-0109(a), 086.a-0204(a)), and at the w. m. keck observatory which is operated as a scientific partnership among the california institute of technology, the university of california and the national aeronautics and space administration. the observatory was made possible by the generous financial support of the w. m. keck foundation. keck telescope time was partially granted by noao, through the telescope system instrumentation program (tsip). tsip is funded by nsf. | the most metal-poor damped lyα systems: an insight into dwarf galaxies at high-redshift |
we present the first results of a survey for high-redshift, z ≥ 6, quasars using izy multicolour photometric observations from the dark energy survey (des). here we report the discovery and spectroscopic confirmation of the zab, yab = 20.2, 20.2 (m1450 = -26.5) quasar des j0454-4448 with a redshift of z = 6.09±0.02 based on the onset of the ly α forest and an h i near zone size of 4.1_{-1.2}^{+1.1} proper mpc. the quasar was selected as an i-band drop out with i-z = 2.46 and zab < 21.5 from an area of ∼300 deg2. it is the brightest of our 43 candidates and was identified for spectroscopic follow-up solely based on the des i-z and z-y colours. the quasar is detected by wise and has w1ab = 19.68. the discovery of one spectroscopically confirmed quasar with 5.7 < z < 6.5 and zab ≤ 20.2 is consistent with recent determinations of the luminosity function at z ∼ 6. des when completed will have imaged ∼5000 deg2 to yab = 23.0 (5σ point source) and we expect to discover 50-100 new quasars with z > 6 including 3-10 with z > 7 dramatically increasing the numbers of quasars currently known that are suitable for detailed studies. | des j0454-4448: discovery of the first luminous z ≥ 6 quasar from the dark energy survey |
we conduct a pilot investigation to determine the optimal combination of color and variability information to identify quasars in current and future multi-epoch optical surveys. we use a bayesian quasar selection algorithm to identify 35,820 type 1 quasar candidates in a 239 {{deg}}2 field of the sloan digital sky survey (sdss) stripe 82, using a combination of optical photometry and variability. color analysis is performed on 5-band single- and multi-epoch sdss optical photometry to a depth of r∼ 22.4. from these data, variability parameters are calculated by fitting the structure function of each object in each band with a power-law model using 10 to \gt 100 observations over timescales from ∼1 day to ∼8 years. selection was based on a training sample of 13,221 spectroscopically confirmed type-1 quasars, largely from the sdss. using variability alone, colors alone, and combining variability and colors we achieve 91%, 93%, and 97% quasar completeness and 98%, 98%, and 97% efficiency, respectively, with particular improvement in the selection of quasars at 2.7\lt z\lt 3.5 where quasars and stars have similar optical colors. the 22,867 quasar candidates that are not spectroscopically confirmed reach a depth of i∼ 22.0; 21,876 (95.7%) are dimmer than coadded i-band magnitude of 19.9, the cutoff for spectroscopic follow-up for sdss on stripe 82. brighter than 19.9, we find 5.7% more quasar candidates without confirming spectra in sky regions otherwise considered complete. the resulting quasar sample has sufficient purity (and statistically correctable incompleteness) to produce a luminosity function comparable to those determined by spectroscopic investigations. we discuss improvements that can be made to the process in preparation for performing similar photometric selection and science on data from post-sdss sky surveys. | quasar classification using color and variability |
we present the cross-correlation between 151 luminous quasars (muv < -26) and 179 protocluster candidates at z ∼ 3.8, extracted from the wide imaging survey (∼121 deg2) performed as part of the hyper suprime-cam subaru strategic program (hsc-ssp). we find that only two out of 151 quasars reside in regions that are more overdense compared to the average field at >4 σ. the distributions of the distances between quasars and the nearest protoclusters and the significance of the overdensity at the positions of quasars are statistically identical to those found for g-dropout galaxies, suggesting that quasars tend to reside in almost the same environment as star-forming galaxies at this redshift. using stacking analysis, we find that the average density of g-dropout galaxies around quasars is slightly higher than that around g-dropout galaxies on 1.0-2.5 pmpc scales, while at <0.5 pmpc that around quasars tends to be lower. we also find that quasars with higher uv luminosity or with more massive black holes tend to avoid the most overdense regions, and that the quasar near-zone sizes are anti-correlated with overdensity. these findings are consistent with a scenario in which luminous quasars at z ∼ 4 reside in structures that are less massive than those expected for the progenitors of today's rich clusters of galaxies, and possibly that luminous quasars may be suppressing star formation in their close vicinity. | luminous quasars do not live in the most overdense regions of galaxies at z ∼ 4 |
we present a catalogue of alma flux density measurements of 754 calibrators observed between 2012 august and 2017 september, for a total of 16263 observations in different bands and epochs. the flux densities were measured by reprocessing the alma images generated in the framework of the almacal project, with a new code developed by the italian node of the european alma regional centre. a search in the online data bases yielded redshift measurements for 589 sources (∼78 per cent of the total). almost all sources are flat spectrum, based on their low-frequency spectral index, and have properties consistent with being blazars of different types. to illustrate the properties of the sample, we show the redshift and flux density distributions as well as the distributions of the number of observations of individual sources and of timespans in the source frame for sources observed in bands 3 (84-116 ghz) and 6 (211-275 ghz). as examples of the scientific investigations allowed by the catalogue, we briefly discuss the variability properties of our sources in alma bands 3 and 6 and the frequency spectra between the effective frequencies of these bands. we find that the median variability index steadily increases with the source-frame time lag increasing from 100 to 800 d, and that the frequency spectra of bl lacs are significantly flatter than those of flat-spectrum radio quasars. we also show the global spectral energy distributions of our sources over 17 orders of magnitude in frequency. | almacal iv: a catalogue of alma calibrator continuum observations |
the reionization of the second electron of helium shapes the physical state of intergalactic gas at redshifts between 2 ≲ z ≲ 5. because performing full in situ radiative transfer in hydrodynamic simulations is computationally expensive for large volumes, the physics of he ii reionization is often approximated by a uniform ultraviolet background model that does not capture the spatial inhomogeneity of reionization. we have devised a model that implements the effects of he ii reionization using semi-analytic calculations of the thermal state of intergalactic gas - a way to bypass a full radiative transfer simulation while still realizing the physics of he ii reionization that affects observables such as the lyman α forest. here, we present a publicly available code that flexibly models inhomogeneous he ii reionization in simulations at a negligible computational cost. because many of the parameters of he ii reionization are uncertain, our model is customizable from a set of free parameters. we show results from this code in mp-gadget, where this model is implemented. we demonstrate the resulting temperature evolution and temperature-density relation of intergalactic gas - consistent with recent measurements and previous radiative transfer simulations. we show that the impact of he ii reionization gives rise to subtle signatures in the 1d statistics of the lyman α forest at the level of several percent, in agreement with previous findings. the flexible nature of these simulations is ideal for studies of he ii reionization and future observations of the he ii lyman α forest. | inhomogeneous he ii reionization in hydrodynamic simulations |
we study the long-term evolution of the global structure of axisymmetric accretion flows onto a black hole (bh) at rates substantially higher than the eddington value ( ${\dot{m}}_{\mathrm{edd}}$ ), performing 2d hydrodynamical simulations with and without radiative diffusion. in the high-accretion optically thick limit, where the radiation energy is efficiently trapped within the inflow, the accretion flow becomes adiabatic and comprises turbulent gas in the equatorial region and strong bipolar outflows. as a result, the mass inflow rate decreases toward the center as ${\dot{m}}_{\mathrm{in}}\propto {r}^{p}$ with p ~ 0.5-0.7 and a small fraction of the inflowing gas feeds the nuclear bh. thus, super-eddington accretion is sustained only when a larger amount of gas is supplied from larger radii at ≳100-1000 $\,{\dot{m}}_{\mathrm{edd}}$ . the global structure of the flow settles down to a quasi-steady state in millions of the orbital timescale at the bh event horizon, which is ≳10-100 times longer than that addressed in previous (magneto-)rhd simulation studies. energy transport via radiative diffusion accelerates the outflow near the poles in the inner region but does not change the overall properties of the accretion flow compared to the cases without diffusion. based on our simulation results, we provide a mechanical feedback model for super-eddington accreting bhs. this can be applied as a subgrid model in large-scale cosmological simulations that do not sufficiently resolve galactic nuclei, and to the formation of the heaviest gravitational-wave sources via accretion in dense environments. | long-term evolution of supercritical black hole accretion with outflows: a subgrid feedback model for cosmological simulations |
we studied the broad-band x-ray spectra of swift/burst alert telescope selected low-accreting active galactic nuclei (agns) using the observations from xmm-newton, swift, and nustar in the energy range of 0.5-150 kev. our sample consists of 30 agns with eddington ratio, λedd < 10-3. we extracted several coronal parameters from the spectral modelling, such as the photon index, hot electron plasma temperature, cutoff energy, and optical depth. we tested whether there exist any correlation/anticorrelation among different spectral parameters. we observe that the relation of hot electron temperature with the cutoff energy in the low accretion domain is similar to what is observed in the high accretion domain. we did not observe any correlation between the eddington ratio and the photon index. we studied the compactness-temperature diagram and found that the cooling process for extremely low-accreting agns is complex. the jet luminosity is calculated from the radio flux, and observed to be related to the bolometric luminosity as $l_{\rm jet} \propto l_{\rm bol}^{0.7}$, which is consistent with the standard radio-x-ray correlation. | coronal properties of low-accreting agns using swift, xmm-newton, and nustar observations |
radio-loud compact radio sources (crss) are characterised by morphological compactness of the jet structure centred on the active nucleus of the galaxy. most of the local elliptical galaxies are found to host a crs with nuclear luminosities lower than those of typical quasars, ≲1042ergs-1 . recently, low-luminosity crss with a liner-like optical spectrum have been named fanaroff-riley (fr) type 0 to highlight their lack of substantially extended radio emission at kpc scales, in contrast with the other fanaroff-riley classes, full-fledged fr is and fr ii radio galaxies. fr 0s are the most abundant class of radio galaxies in the local universe, and characterised by a higher core dominance, poorer mpc-scale environment and smaller (sub-kpc scale, if resolved) jets than fr is. however, fr 0s share similar host and nuclear properties with fr is. a different accretion-ejection paradigm from that in place in fr is is invoked to account for the parsec-scale fr 0 jets. this review revises the state-of-the-art knowledge about fr 0s, their nature, and which open issues the next generation of radio telescopes can solve in this context. | the nature of compact radio sources: the case of fr 0 radio galaxies |
the formation of the large-scale structure, the evolution and distribution of galaxies, quasars, and dark matter on cosmological scales, requires numerical simulations. differentiable simulations provide gradients of the cosmological parameters, that can accelerate the extraction of physical information from statistical analyses of observational data. the deep learning revolution has brought not only myriad powerful neural networks, but also breakthroughs including automatic differentiation (ad) tools and computational accelerators like gpus, facilitating forward modeling of the universe with differentiable simulations. because ad needs to save the whole forward evolution history to backpropagate gradients, current differentiable cosmological simulations are limited by memory. using the adjoint method, with reverse time integration to reconstruct the evolution history, we develop a differentiable cosmological particle-mesh (pm) simulation library pmwd (particle-mesh with derivatives) with a low memory cost. based on the powerful ad library jax, pmwd is fully differentiable, and is highly performant on gpus. | pmwd: a differentiable cosmological particle-mesh $n$-body library |
baikal-gvd has recently published its first measurement of the diffuse astrophysical neutrino flux, performed using high-energy cascade-like events. we further explore the baikal-gvd cascade data set collected in 2018-2022, with the aim to identify possible associations between the baikal-gvd neutrinos and known astrophysical sources. we leverage the relatively high angular resolution of the baikal-gvd neutrino telescope (2-3 deg.), made possible by the use of liquid water as the detection medium, enabling the study of astrophysical point sources even with cascade events. we estimate the telescope's sensitivity in the cascade channel for high-energy astrophysical sources and refine our analysis prescriptions using monte-carlo simulations. we primarily focus on cascades with energies exceeding 100 tev, which we employ to search for correlation with radio-bright blazars. although the currently limited neutrino sample size provides no statistically significant effects, our analysis suggests a number of possible associations with both extragalactic and galactic sources. specifically, we present an analysis of an observed triplet of neutrino candidate events in the galactic plane, focusing on its potential connection with certain galactic sources, and discuss the coincidence of cascades with several bright and flaring blazars. | search for directional associations between baikal gigaton volume detector neutrino-induced cascades and high-energy astrophysical sources |
the range of currently proposed active galactic nucleus (agn) far-infrared templates results in uncertainties in retrieving host galaxy information from infrared observations and also undermines constraints on the outer part of the agn torus. we discuss how to test and reconcile these templates. physically, the fraction of the intrinsic agn ir-processed luminosity compared with that from the central engine should be consistent with the dust-covering factor. in addition, besides reproducing the composite spectral energy distributions (seds) of quasars, a correct agn ir template combined with an accurate library of star-forming galaxy templates should be able to reproduce the ir properties of the host galaxies, such as the luminosity-dependent sed shapes and aromatic feature strengths. we develop tests based on these expected behaviors and find that the shape of the agn intrinsic far-ir emission drops off rapidly starting at ∼20 μm and can be matched by an elvis et al.-like template with a minor modification. despite the variations in the near- to mid-ir bands, agns in quasars and seyfert galaxies have remarkably similar intrinsic far-ir seds at λ ∼ 20-100 μm, suggesting a similar emission character of the outermost region of the circumnuclear torus. the variations of the intrinsic agn ir seds among the type-1 quasar population can be explained by the changing relative strengths of four major dust components with similar characteristic temperatures, and there is evidence for compact agn-heated dusty structures at sub-kiloparsec scales in the far-ir. | the intrinsic far-infrared continua of type-1 quasars |
recent observations indicate a $4.9\sigma$ tension between the cmb and quasar dipoles. this tension challenges the cosmological principle. we propose that if we live in a gigaparsec scale void, the cmb and quasar dipolar tension can be reconciled. this is because we are unlikely to live at the center of the void. and a 15% offset from the center will impact the quasars and cmb differently in their dipolar anisotropies. as we consider a large and thick void, our setup can also ease the hubble tension. | reconciling cosmic dipolar tensions with a gigaparsec void |
in this paper, we investigate the cosmic anisotropy from the sn-q sample, consisting of the pantheon sample and quasars, by employing the hemisphere comparison (hc) method and the dipole fitting (df) method. compared to the pantheon sample, the new sample has a larger redshift range, a more homogeneous distribution, and a larger sample size. for the hc method, we find that the maximum anisotropy level is almax = 0.142 ± 0.026 in the direction (l, b) = (316.08°-129.48+27.41, 4.53°-64.06+26.29). the magnitude of anisotropy is a = (-8.46-5.51+4.34) × 10-4 and the corresponding preferred direction points toward (l, b) = (29.31°-30.54+30.59, 71.40°-9.72+9.79) for the quasar sample from the df method. the combined sn and quasar sample is consistent with the isotropy hypothesis. the distribution of the dataset might impact the preferred direction from the dipole results. the result is weakly dependent on the redshift from the redshift tomography analysis. there is no evidence of cosmic anisotropy in the sn-q sample. though some results obtained from the quasar sample are not consistent with the standard cosmological model, we still do not find any distinct evidence of cosmic anisotropy in the sn-q sample. | testing cosmic anisotropy with pantheon sample and quasars at high redshifts |
the universe is largely transparent to γ -rays in the gev energy range, making these high-energy photons valuable for exploring energetic processes in the cosmos. after 7 years of operation, the fermi gamma-ray space telescope has produced a wealth of information about the high-energy sky. this review focuses on extragalactic γ -ray sources: what has been learned about the sources themselves and about how they can be used as cosmological probes. active galactic nuclei (blazars, radio galaxies, seyfert galaxies) and star-forming galaxies populate the extragalactic high-energy sky. fermi observations have demonstrated that these powerful non-thermal sources display substantial diversity in energy spectra and temporal behavior. coupled with contemporaneous multifrequency observations, the fermi results are enabling detailed, time-dependent modeling of the energetic particle acceleration and interaction processes that produce the γ -rays, as well as providing indirect measurements of the extragalactic background light and intergalactic magnetic fields. population studies of the γ -ray source classes compared to the extragalactic γ -ray background place constraints on some models of dark matter. ongoing searches for the nature of the large number of γ -ray sources without obvious counterparts at other wavelengths remain an important challenge. | the extragalactic gamma-ray sky in the fermi era |
photometric redshifts play an important role as a measure of distance for various cosmological topics. spectroscopic redshifts are only available for a very limited number of objects but can be used for creating statistical models. a broad variety of photometric catalogues provide uncertain low resolution spectral information for galaxies and quasars that can be used to infer a redshift. many different techniques have been developed to produce those redshift estimates with increasing precision. instead of providing a point estimate only, astronomers start to generate probabilistic density functions (pdfs) which should provide a characterisation of the uncertainties of the estimation. in this work we present two simple approaches on how to generate those pdfs. we use the example of generating the photometric redshift pdfs of quasars from sdss(dr7) to validate our approaches and to compare them with point estimates. we do not aim for presenting a new best performing method, but we choose an intuitive approach that is based on well known machine learning algorithms. furthermore we introduce proper tools for evaluating the performance of pdfs in the context of astronomy. the continuous ranked probability score (crps) and the probability integral transform (pit) are well accepted in the weather forecasting community. both tools reflect how well the pdfs reproduce the real values of the analysed objects. as we show, nearly all currently used measures in astronomy show severe weaknesses when used to evaluate pdfs. | uncertain photometric redshifts |
mrk 590 was originally classified as a seyfert 1 galaxy, but then it underwent dramatic changes: the nuclear luminosity dropped by over two orders of magnitude and the broad emission lines all but disappeared from the optical spectrum. here we present follow-up observations to the original discovery and characterization of this “changing-look” active galactic nucleus (agn). the new chandra and hubble space telescope observations from 2014 show that mrk 590 is awakening, changing its appearance again. while the source continues to be in a low state, its soft excess has re-emerged, though not to the previous level. the uv continuum is brighter by more than a factor of two and the broad mg ii emission line is present, indicating that the ionizing continuum is also brightening. these observations suggest that the soft excess is not due to reprocessed hard x-ray emission. instead, it is connected to the uv continuum through warm comptonization. variability of the fe kα emission lines suggests that the reprocessing region is within ∼10 lt-yr or 3 pc of the central source. the change in agn type is neither due to obscuration nor due to one-way evolution from type 1 to type 2, as suggested in the literature, but may be related to episodic accretion events. | the changing-look quasar mrk 590 is awakening |
in this article, we elaborate further on the λ cdm "tension", suggested recently by the authors lusso et al. (astron astrophys 628:l4, 2019) and risaliti and lusso (nat astron 3(3):272, 2019). we combine supernovae type ia (snia) with quasars (qso) and gamma ray bursts (grb) data in order to reconstruct in a model independent way the hubble relation to as high redshifts as possible. specifically, in the case of either snia or snia/qso data we find that the current values of the cosmokinetic parameters extracted from the gaussian process are consistent with those of λ cdm. including grbs in the analysis we find a tension, which lies between 2 σ and 3 σ levels respectively. finally, we find that at high redshifts (z >1 ) the corresponding cosmokinetic parameters significantly deviate from those of λ cdm, hence the possibility of new physics is not precluded by the present analysis. | does λ cdm really be in tension with the hubble diagram data? |
the hubble space telescope/cosmic origins spectrograph (cos) has opened a new discovery space for studying quasar absorption outflows and their contribution to active galactic nucleus (agn) feedback. specifically, cos provides high-quality far-ultraviolet (fuv) spectra covering the diagnostic-rich 500-1050 å rest frame (hereafter, euv500) of medium redshift objects. the quality and quantity of euv500 diagnostic troughs allow us to probe the very high-ionization phase, which carries 90% or more of the outflowing material, as well as to determine the distance of most outflows from the central source (r). the first objective is impossible to achieve with ground-based spectra, and r can be measured in only ∼1% of them. here, we summarize the main results of the first dedicated survey of such outflows, including the following. | hst/cos observations of quasar outflows in the 500-1050 å rest frame. i. the most energetic outflows in the universe and other discoveries |
dense gas in the centre of galaxies feeds massive black holes, but can also become a source of obscuration and limit our ability to find faint active galactic nuclei (agn). we use a high-resolution cosmological radiative hydrodynamics simulation to connect the properties of the gas in the central region (a few tens of parsec) of a high-redshift galaxy to the growth of a massive black hole during the first billion years of the universe. we find that the feedback from the agn efficiently controls the growth of the black hole and limits the duration of the high accretion episodes by emptying the gas reservoir. as the galaxy grows in mass, the production of metals results in the presence of dust-enriched gas in the galaxy centre that can obscure highly accreting black holes enough to strongly reduce their uv/optical visibility. we also find that the gas outside the very centre of the galaxy can contribute to the total column density and obscuration at a level at least comparable to the gas in the nuclear region. we suggest that this explains the different duty-cycles required to explain the masses of high-redshift quasars and the observed uv/optical luminosity functions: in our case, the agn would be observed with an x-ray luminosity above l_x = 10^{42} erg s^{-1} around 30 per cent of the time, but with uv magnitude brighter than m1450 = -23 only 4 per cent of the time. | black hole obscuration and duty-cycles mediated by agn feedback in high-redshift galaxies |
winds outflowing from active galactic nuclei (agns) may carry significant amounts of mass and energy out to their host galaxies. in this paper we report the detection of a sub-relativistic outflow observed in the narrow line seyfert 1 galaxy iras 17020+4544 as a series of absorption lines corresponding to at least five absorption components with an unprecedented wide range of associated column densities and ionization levels and velocities in the range of 23,000-33,000 km s-1, detected at x-ray high spectral resolution (e/δe ∼ 1000) with the esa's observatory xmm-newton. the charge states of the material constituting the wind clearly indicate a range of low to moderate ionization states in the outflowing gas and column densities that are significantly lower than observed in highly ionized ultra-fast outflows. we estimate that at least one of the outflow components may carry sufficient energy to substantially suppress star formation and heat the gas in the host galaxy. iras 17020+4544 therefore provides an interesting example of feedback by a moderately luminous agn that is hosted in a spiral galaxy, a case barely envisaged in most evolution models, which often predict that feedback processes take place in massive elliptical galaxies hosting luminous quasars in a post-merger phase. | x-ray high-resolution spectroscopy reveals feedback in a seyfert galaxy from an ultra-fast wind with complex ionization and velocity structure |
almost every helium atom in the universe was created just a few minutes after the big bang through a process commonly referred to as big bang nucleosynthesis1,2. the amount of helium that was made during big bang nucleosynthesis is determined by combining particle physics and cosmology3. the current leading measures of the primordial helium abundance (yp) are based on the relative strengths of h uc(i) and he uc(i) emission lines emanating from star-forming regions in local metal-poor galaxies4-7. as the statistical errors on these measurements improve, it is essential to test for systematics by developing independent techniques. here we report a determination of the primordial helium abundance based on a near-pristine intergalactic gas cloud that is seen in absorption against the light of a background quasar. this gas cloud, observed when the universe was just one-third of its present age (zabs = 1.724), has a metal content around 100 times less than that of the sun, and at least 30% less metal content than the most metal-poor h uc(ii) region currently known where a determination of the primordial helium abundance is possible. we conclude that the helium abundance of this intergalactic gas cloud is y =0.25 0-0.025+0.033 , which agrees with the standard model primordial value8-10, yp = 0.24672 ± 0.00017. our determination of the primordial helium abundance is not yet as precise as that derived using metal-poor galaxies, but our method has the potential to offer a competitive test of physics beyond the standard model during big bang nucleosynthesis. | measurement of the primordial helium abundance from the intergalactic medium |
in this paper, we carry out an assessment of cosmic distance duality relation (cddr) based on the latest observations of hii galaxies acting as standard candles and ultra-compact structure in radio quasars acting as standard rulers. particularly, two machine learning reconstruction methods [gaussian process (gp) and artificial neural network (ann)] are applied to reconstruct the hubble diagrams from observational data. we show that both approaches are capable of reconstructing the current constraints on possible deviations from the cddr in the redshift range z ∼2.3 . considering four different parametric methods of cddr, which quantify deviations from the cddr and the standard cosmological model, we compare the results of the two different machine learning approaches. it is observed that the validity of cddr is in well agreement with the current observational data within 1 σ based on the reconstructed distances through gp in the overlapping redshift domain. moreover, we find that ultra-compact radio quasars could provide 10-3-level constraints on the violation parameter at high redshifts, when combined with the observations of hii galaxies. in the framework of ann, one could derive robust constraints on the violation parameter at a precision of 10-2, with the validity of such distance duality relation within 2 σ confidence level. | revisiting the cosmic distance duality relation with machine learning reconstruction methods: the combination of hii galaxies and ultra-compact radio quasars |
we present observations of ionized gas outflows in 11 z = 1.39-2.59 radio-loud quasar host galaxies. data were taken with the integral field spectrograph osiris and the adaptive optics system at the w.m. keck observatory targeting nebular emission lines (hβ, [o iii], hα, [n ii], and [s ii]) redshifted into the near-infrared (1-2.4 μm). outflows with velocities of 500-1700 km s-1 are detected in 10 systems on scales ranging from <1 kpc to 10 kpc with outflow rates from 8-2400 m⊙ yr-1 . for five sources, the outflow momentum rates are 4-80 times lagn/c, consistent with outflows being driven by an energy-conserving shock. the five other outflows are either driven by radiation pressure or an isothermal shock. the outflows are the dominant source of gas depletion, and we find no evidence for star formation along the outflow paths. for eight objects, the outflow paths are consistent with the orientation of the jets. yet, given the calculated pressures, we find no evidence of the jets currently doing work on these galactic-scale ionized outflows. we find that galactic-scale feedback occurs well before galaxies establish a substantial fraction of their stellar mass, as expected from local scaling relationships. | a spatially resolved survey of distant quasar host galaxies. i. dynamics of galactic outflows |
we report atacama large millimeter/submillimeter array (alma) observations of the dust continuum and [c ii] emission of the host galaxy of j0439+1634, a gravitationally lensed quasar at z = 6.5. gravitational lensing boosts the source-plane resolution to ~0"15 (~0.8 kpc). the lensing model derived from the alma data is consistent with the fiducial model in fan et al. based on hst imaging. the host galaxy of j0439+1634 can be well-fitted by a sérsic profile consistent with an exponential disk, both in the far-infrared (fir) continuum and the [c ii] emission. the overall magnification is 4.53 ± 0.05 for the continuum and 3.44 ± 0.05 for the [c ii] line. the host galaxy of j0439+1634 is a compact ultraluminous infrared galaxy, with a total star formation rate (sfr) of 1.56 × 103m⊙ yr-1 after correcting for lensing and an effective radius of 0.74 kpc. the resolved regions in j0439+1634 follow the "[c ii] deficit," where the [c ii]-to-fir ratio decreases with fir surface brightness. the reconstructed velocity field of j0439+1634 appears to be rotation-like. the maximum line-of-sight rotation velocity is 130 km s-1 at a radius of 2 kpc. however, our data cannot be fit by an axisymmetric thin rotating disk, and the inclination of the rotation axis, i, remains unconstrained. we estimate the dynamical mass of the host galaxy to be $7.9{\sin }^{-2}(i)\times {10}^{9}{m}_{\odot }$ . j0439+1634 is likely to have a high gas-mass fraction and an oversized smbh compared to local relations. the sfr of j0439+1634 reaches the maximum possible values, and the sfr surface density is close to the highest value seen in any star-forming galaxy currently known in the universe. | alma observations of the sub-kpc structure of the host galaxy of a z = 6.5 lensed quasar: a rotationally supported hyper-starburst system at the epoch of reionization |
we measure the location and evolutionary vectors of 69 herschel-detected broad-line active galactic nuclei (blagns) in the {{m}bh}-{{m}*} plane. blagns are selected from the cosmos and cdf-s fields, and span the redshift range 0.2≤slant z\lt 2.1. black hole masses are calculated using archival spectroscopy and single-epoch virial mass estimators, and galaxy total stellar masses are calculated by fitting the spectral energy distribution (subtracting the blagn component). the mass-growth rates of both the black hole and galaxy are calculated using chandra/xmm-newton x-ray and herschel far-infrared data, reliable measures of the blagn accretion and galaxy star formation rates, respectively. we use monte carlo simulations to account for biases in our sample, due to both selection limits and the steep slope of the massive end of the galaxy stellar-mass distribution. we find our sample is consistent with no evolution in the {{m}bh}-{{m}*} relation from z ∼ 2 to z ∼ 0. blagns and their host galaxies which lie off the black hole mass-galaxy total stellar mass relation tend to have evolutionary vectors anti-correlated with their mass ratios: that is, galaxies with over-massive (under-massive) black holes tend to have a low (high) ratio of the specific accretion rate to the specific star formation rate. we also use the measured growth rates to estimate the preferred agn duty cycle for our galaxies to evolve most consistently onto the local {{m}bh}-{{m}bul} relation. under reasonable assumptions of exponentially declining star formation histories, the data suggest a non-evolving (no more than a factor of a few) blagn duty cycle among star-forming galaxies of ∼10% (1σ range of 1-42% at z\lt 1 and 2-34% at z\gt 1). | evolution in the black hole—galaxy scaling relations and the duty cycle of nuclear activity in star-forming galaxies |
the brightest southern quasar above redshift z = 1, he 0515-4414, with its strong intervening metal absorption line system at zabs = 1.1508, provides a unique opportunity to precisely measure or limit relative variations in the fine-structure constant (δα/α). a variation of just ∼3 parts per million (ppm) would produce detectable velocity shifts between its many strong metal transitions. using new and archival observations from the ultraviolet and visual echelle spectrograph (uves), we obtain an extremely high signal-to-noise ratio spectrum (peaking at s/n ≈ 250 pix-1). this provides the most precise measurement of δα/α from a single absorption system to date, δα/α = -1.42 ± 0.55stat ± 0.65sys ppm, comparable with the precision from previous, large samples of ∼150 absorbers. the largest systematic error in all (but one) previous similar measurements, including the large samples, was long-range distortions in the wavelength calibration. these would add an ∼2 ppm systematic error to our measurement and up to ∼10 ppm to other measurements using mg and fe transitions. however, we corrected the uves spectra using well-calibrated spectra of the same quasar from the high accuracy radial velocity planet searcher, leaving a residual 0.59 ppm systematic uncertainty, the largest contribution to our total systematic error. a similar approach, using short observations on future well-calibrated spectrographs to correct existing high s/n spectra, would efficiently enable a large sample of reliable δα/α measurements. the high-s/n uves spectrum also provides insights into analysis difficulties, detector artefacts and systematic errors likely to arise from 25-40-m telescopes. | high-precision limit on variation in the fine-structure constant from a single quasar absorption system |
we present new muse observations of a galaxy group probed by a background quasar. the quasar sightline passes between multiple z = 0.28 galaxies, whilst showing at the same redshift low-ionized metal line species, including ca ii, mg i, mg ii and fe ii. based on the galaxy redshifts measured from the muse data, we estimate the galaxies to be part of a small galaxy group with a halo mass of ≈6 × 1012 m⊙. we use the muse data to reveal the two-dimensional dynamical properties of the gas and stars in the group galaxies, and relate these to the absorber kinematics. with these data, we consider a number of scenarios for the nature of the gas probed by the sightline absorbers: a corotating gas halo associated with a single galaxy within the group; outflowing material from a single group member powered by recent star-formation; and cool dense gas associated with an intra-group medium. we find that the dynamics, galaxy impact parameters, star formation rates and the absorber strength suggest that the cool gas cannot be clearly associated with any single galaxy within the group. instead, we find that the observations are consistent with a superposition of cool gas clouds originating with the observed galaxies as they fall into the group potential, and are now likely in the process of forming the intra-group medium. | probing the intra-group medium of a z = 0.28 galaxy group |
we present a tentative detection of the large-scale structure of ly α emission in the universe at redshifts z = 2-3.5 by measuring the cross-correlation of ly α surface brightness with quasars in sloan digital sky survey/baryon oscillation spectroscopic survey. we use a million spectra targeting luminous red galaxies at z < 0.8, after subtracting a best-fitting model galaxy spectrum from each one, as an estimate of the high-redshift ly α surface brightness. the quasar-ly α emission cross-correlation is detected on scales 1 ∼ 15 h-1 mpc, with shape consistent with a λcdm model with ω _m =0.30^{+0.10}_{-0.07}. the predicted amplitude of this cross-correlation is proportional to the product of the mean ly α surface brightness, <μα>, the amplitude of mass fluctuations and the quasar and ly α emission bias factors. we infer <μα> (bα/3) = (3.9 ± 0.9) × 10-21 erg s-1 cm-2 å-1 arcsec-2, where bα is the ly α emission bias. if star-forming galaxies dominate this emission, we find ρsfr = (0.28 ± 0.07)(3/bα) yr-1 mpc-3. for bα = 3, this value is ∼30 times larger than previous estimates from individually detected ly α emitters, but consistent with the total ρsfr derived from dust-corrected, continuum uv galaxy surveys, if most of the ly α photons from these galaxies avoid dust absorption and are reemitted after diffusing in large gas haloes. heating of intergalactic gas by he ii photoionization from quasar radiation or jets may alternatively explain the detected correlation, and cooling radiation from gas in galactic haloes may also contribute. we also detect redshift space anisotropy of the quasar-ly α emission cross-correlation, finding evidence at the 3.0σ level that it is radially elongated, which may be explained by radiative-transfer effects. our measurements represent the first application of the intensity mapping technique to optical observations. | large-scale clustering of lyman α emission intensity from sdss/boss |
hot dust-obscured galaxies (hot dogs), selected from wide-field infrared survey explorer’s all-sky infrared survey, host some of the most powerful active galactic nuclei known and may represent an important stage in the evolution of galaxies. most known hot dogs are located at z> 1.5, due in part to a strong bias against identifying them at lower redshift related to the selection criteria. we present a new selection method that identifies 153 hot dog candidates at z∼ 1, where they are significantly brighter and easier to study. we validate this approach by measuring a redshift z = 1.009 and finding a spectral energy distribution similar to that of higher-redshift hot dogs for one of these objects, wise j1036+0449 ({l}{bol}≃ 8× {10}46 {erg} {{{s}}}-1). we find evidence of a broadened component in mg ii, which would imply a black hole mass of {m}{bh}≃ 2× {10}8 {m}⊙and an eddington ratio of {λ }{edd}≃ 2.7. wise j1036+0449 is the first hot dog detected by the nuclear spectroscopic telescope array, and observations show that the source is heavily obscured, with a column density of {n}{{h}}≃ (2{--}15)× {10}23 {{cm}}-2. the source has an intrinsic 2-10 kev luminosity of ∼ 6× {10}44 {erg} {{{s}}}-1, a value significantly lower than that expected from the mid-infrared/x-ray correlation. we also find that other hot dogs observed by x-ray facilities show a similar deficiency of x-ray flux. we discuss the origin of the x-ray weakness and the absorption properties of hot dogs. hot dogs at z≲ 1 could be excellent laboratories to probe the characteristics of the accretion flow and of the x-ray emitting plasma at extreme values of the eddington ratio. | nustar observations of wise j1036+0449, a galaxy at z~1 obscured by hot dust |
we study the correlation between the [o iii] λ5007 and x-ray luminosities of local active galactic nuclei (agns), using a complete, hard x-ray (>10 kev) selected sample in the swift/bat 9-month catalog. from our optical spectroscopic observations at the south african astronomical observatory and the literature, a catalog of [o iii] λ5007 line flux for all 103 agns at galactic latitudes of | b| \gt 15^\circ is compiled. significant correlations with intrinsic x-ray luminosity ({l}{{x}}) are found for both observed ({l}[{{o} {{iii}}] }) and extinction-corrected ({l}[{{o} {{iii}}]}{{cor}}) luminosities, separately for x-ray unabsorbed and absorbed agns. we obtain the regression form of {l}[{{o} {{iii}}] } \propto \{l}2-10\{kev}1.18+/- 0.07 and {l}[{{o} {{iii}}]}{{cor}} \propto \{l}2-10\{kev}1.16+/- 0.09 from the whole sample. the absorbed agns with low (<0.5%) scattering fractions in soft x-rays show on average smaller {l}[{{o} {{iii}}]}/{l}{{x}} and {l}[{{o} {{iii}}]}{{cor}}/{l}{{x}} ratios than the other absorbed agns, while those in edge-on host galaxies do not. these results suggest that a significant fraction of this population is buried in tori with small opening angles. by using these {l}[{{o} {{iii}}] } versus {l}{{x}} correlations, the x-ray luminosity function (lf) of local agns (including compton-thick agns) in a standard population synthesis model gives much better agreement with the [o iii] λ5007 lf derived from the sloan digital sky survey than previously reported. this confirms that hard x-ray observations are a very powerful tool to find agns with high completeness. | [o iii] λ5007 and x-ray properties of a complete sample of hard x-ray selected agns in the local universe |
we investigate systematically the x-ray emission from type 1 quasars using a sample of 1825 sloan digital sky survey non-broad absorption line (non-bal) quasars with chandra archival observations. a significant correlation is found between the x-ray-to-optical power-law slope parameter (αox) and the 2500 å monochromatic luminosity (l2500å), and the x-ray weakness of a quasar is assessed via the deviation of its αox value from that expected from this relation. we demonstrate the existence of a population of non-bal x-ray-weak quasars, and the fractions of quasars that are x-ray weak by factors of ≥6 and ≥10 are 5.8% ± 0.7% and 2.7% ± 0.5%, respectively. we classify x-ray-weak quasars (x-ray weak by factors of ≥6) into three categories based on their optical spectral features: weak emission-line quasars (wlqs; c iv rest-frame equivalent width < 16 å), red quasars (δ(g - i) > 0.2), and unclassified x-ray-weak quasars. the x-ray-weak fraction of ${35}_{-9}^{+12} \% $ within the wlq population is significantly higher than that within non-wlqs, confirming previous findings that wlqs represent one population of x-ray-weak quasars. the x-ray-weak fraction of ${13}_{-3}^{+5} \% $ within the red quasar population is also considerably higher than that within the normal quasar population. the unclassified x-ray-weak quasars do not have unusual optical spectral features, and their x-ray weakness may be mainly related to quasar x-ray variability. | on the fraction of x-ray-weak quasars from the sloan digital sky survey |
this letter reports the discovery of spatially extended line-emitting nebula, reaching to ≈100 physical kpc (pkpc) from a damped {ly}α absorber (dla) at z dla = 0.313 along the sightline toward quasi-stellar object (qso) pks 1127-145 (z qso = 1.188). this dla was known to be associated with a galaxy group of dynamical mass m group ∼ 3 × 1012 m ⊙, but its physical origin remained ambiguous. new wide-field integral field observations revealed a giant nebula detected in [o ii], hβ, [o iii], hα, and [n ii] emission, with the line-emitting gas following closely the motions of group galaxies. one of the denser streams passes directly in front of the qso with kinematics that are consistent with the absorption profiles recorded in the qso echelle spectra. the emission morphology, kinematics, and line ratios of the nebula suggest that shocks and turbulent mixing layers, produced as a result of stripped gaseous streams moving at supersonic speed across the ambient hot medium, contribute significantly to the ionization of the gas. while the dla may not be associated with any specific detected member of the group, both the kinematic and dust properties are consistent with the dla originating in streams of gas stripped from sub-l * group members at ≲25 pkpc from the qso sightline. this study demonstrates that gas stripping in low-mass galaxy groups is effective in releasing metal-enriched gas from star-forming regions, producing absorption systems in qso spectra, and that combining absorption and emission-line observations provides an exciting new opportunity for studying gas and galaxy co-evolution. | a giant intragroup nebula hosting a damped {ly}\\alphaabsorber at z = 0.313 |
we present data on the gas-phase abundances for 9 different elements in the interstellar medium of the small magellanic cloud (smc), based on the strengths of ultraviolet absorption features over relevant velocities in the spectra of 18 stars within the smc. from this information and the total abundances defined by the element fractions in young stars in the smc, we construct a general interpretation on how these elements condense into solid form onto dust grains. as a group, the elements si, s, cr, fe, ni, and zn exhibit depletion sequences similar to those in the local part of our galaxy defined by jenkins. the elements mg and ti deplete less rapidly in the smc than in the milky way, and mn depletes more rapidly. we speculate that these differences might be explained by the different chemical affinities to different existing grain substrates. for instance, there is evidence that the mass fractions of polycyclic aromatic hydrocarbons in the smc are significantly lower than those in the milky way. we propose that the depletion sequences that we observed for the smc may provide a better model for interpreting the element abundances in low-metallicity damped lyman alpha (dla) and sub-dla absorption systems that are recorded in the spectra of distant quasars and gamma-ray burst afterglows. based on observations with the nasa/esa hubble space telescope and additional data obtained from the data archive at the space telescope science institute, which is operated by the associations of universities for research in astronomy, incorporated, under nasa contract nas5-26555. these observations are associated with program nr. 13778. | interstellar gas-phase element depletions in the small magellanic cloud: a guide to correcting for dust in qso absorption line systems |
the angular size of the broad line region (blr) of the nearby active galactic nucleus ngc 3783 has been spatially resolved by recent observations with vlti/gravity. a reverberation mapping (rm) campaign has also recently obtained high quality light curves and measured the linear size of the blr in a way that is complementary to the gravity measurement. the size and kinematics of the blr can be better constrained by a joint analysis that combines both gravity and rm data. this, in turn, allows us to obtain the mass of the supermassive black hole in ngc 3783 with an accuracy that is about a factor of two better than that inferred from gravity data alone. we derive mbh = 2.54−0.72+0.90 × 107 m⊙. finally, and perhaps most notably, we are able to measure a geometric distance to ngc 3783 of 39.9−11.9+14.5 mpc. we are able to test the robustness of the blr-based geometric distance with measurements based on the tully-fisher relation and other indirect methods. we find the geometric distance is consistent with other methods within their scatter. we explore the potential of blr-based geometric distances to directly constrain the hubble constant, h0, and identify differential phase uncertainties as the current dominant limitation to the h0 measurement precision for individual sources. | a geometric distance to the supermassive black hole of ngc 3783 |
we test the anisotropy in the finslerian cosmological model with the x-ray and ultraviolet (uv) fluxes of quasars. the 2015 and 2020 compilations of quasars are used in the cosmological constraints. we find that the dipole direction given by the 2015 quasar compilation is not far away from the one provided by the pantheon sample and the angular differences are around 30∘. the pantheon sample is combined with quasars as the "standardized candles" to test the cosmic anisotropy. the results from two combined datasets are consistent. they show that the dipole anisotropy is weak in the finslerian cosmological model. we investigate the hubble constant h0 in the finslerian cosmological model. though the central value of h0 from the combination of six gravitationally lensed quasars, pantheon sample, and 2020 quasar compilation decreases a little bit, it is consistent with the result from six gravitationally lensed quasars within statistical uncertainties. | constraining the anisotropy of the universe with the x-ray and uv fluxes of quasars |
we present space-vlbi radioastron observations at 1.6 ghz and 4.8 ghz of the flat spectrum radio quasar 3c 273, with detections on baselines up to 4.5 and 3.3 earth diameters, respectively. achieving the best angular resolution at 1.6 ghz to date, we have imaged limb-brightening in the jet, not previously detected in this source. in contrast, at 4.8 ghz, we detected emission from a central stream of plasma, with a spatial distribution complementary to the limb-brightened emission, indicating an origin in the spine of the jet. while a stratification across the jet width in the flow density, internal energy, magnetic field, or bulk flow velocity are usually invoked to explain the limb-brightening, the different jet structure detected at the two frequencies probably requires a stratification in the emitting electron energy distribution. future dedicated numerical simulations will allow the determination of which combination of physical parameters are needed to reproduce the spine-sheath structure observed by space-vlbi with radioastron in 3c 273. | radioastron reveals a spine-sheath jet structure in 3c 273 |
based on results by recent surveys, the number of bright quasars at redshifts z > 3 is being constantly revised upward. the current consensus is that at bright magnitudes (m1450 ≤ -27) the number densities of such sources could have been underestimated by a factor of 30%-40%. in the framework of the qubrics survey, we identified 58 bright qsos at 3.6 ≤ z ≤ 4.2, with magnitudes ipsf ≤ 18, in an area of 12400 deg2. the uniqueness of our survey is underlined by the fact that it allows us, for the first time, to extend the sampled absolute magnitude range up to m1450 = -29.5. we derived a bright-end slope of β = -4.025 and a space density at <m1450> = -28.75 of 2.61 × 10-10 mpc-3 comoving, after taking into account the estimated incompleteness of our observations. taking into account the results of fainter surveys, active galactic nuclei (agns) brighter than m1450 = -23 could produce at least half of the ionizing emissivity at z ∼ 4. considering a mean escape fraction of 0.7 for the qso and agn population, combined with a mean free path of 41.3 proper mpc at z = 3.9, we derive a photoionization rate of ${\rm{log}}({\rm{\gamma }}\left[{{\rm{s}}}^{-1}\right])=-{12.17}_{-0.07}^{+0.13}$ , produced by agns at m1450 < -18, that is, ∼100% of the measured ionizing background at z ∼ 4. | the luminosity function of bright qsos at z ∼ 4 and implications for the cosmic ionizing background |
on 2019/07/30.86853 ut, icecube detected a high-energy astrophysical neutrino candidate. the flat spectrum radio quasar pks 1502+106 is located within the 50 per cent uncertainty region of the event. our analysis of 15 ghz very long baseline array (vlba) and astrometric 8 ghz vlba data, in a time span prior and after the icecube event, reveals evidence for a radio ring structure that develops with time. several arc-structures evolve perpendicular to the jet ridge line. we find evidence for precession of a curved jet based on kinematic modelling and a periodicity analysis. an outflowing broad line region (blr) based on the c iv line emission (sloan digital sky survey) is found. we attribute the atypical ring to an interaction of the precessing jet with the outflowing material. we discuss our findings in the context of a spine-sheath scenario where the ring reveals the sheath and its interaction with the surroundings (narrow line region, nlr, clouds). we find that the radio emission is correlated with the γ-ray emission, with radio lagging the γ-rays. based on the γ-ray variability time-scale, we constrain the γ-ray emission zone to the blr (30-200 rg) and within the jet launching region. we discuss that the outflowing blr provides the external radiation field for γ-ray production via external compton scattering. the neutrino is most likely produced by proton-proton interaction in the blazar zone (beyond the blr), enabled by episodic encounters of the jet with dense clouds, i.e. some molecular cloud in the nlr. | a ring accelerator? unusual jet dynamics in the icecube candidate pks 1502+106 |
as part of our program to identify host galaxies of known z = 2-3 mg ii absorbers with the keck cosmic web imager (kcwi), we discovered a compact group giving rise to a z = 2.431 dla with ultrastrong mg ii absorption in quasar field j234628+124859. the group consists of four star-forming galaxies within 8-28 kpc and v ~ 40-340 km s-1 of each other, where tidal streams are weakly visible in deep hst imaging. the group geometric centre is d = 25 kpc from the quasar (d = 20-40 kpc for each galaxy). galaxy g1 dominates the group (1.66l*, sfrfuv = 11.6 m⊙ yr-1) while g2, g3, and g4 are less massive (0.1-0.3l*, sfrfuv = 1.4-2.0 m⊙ yr-1). using a vlt/uves quasar spectrum covering the h i lyman series and metal lines such as mg ii, si iii, and c iv, we characterized the kinematic structure and physical conditions along the line of sight with cloud-by-cloud multiphase bayesian modelling. the absorption system has a total $\log (n({{{\rm h}\,\rm{\small i}}})/{\rm cm}^{-2})=20.53$ and an $n({{{\rm h}\,\rm{\small i}}})$-weighted mean metallicity of log (z/z⊙) = -0.68, with a very large mg ii linewidth of δv ~ 700 km s-1. the highly kinematically complex profile is well modelled with 30 clouds across low- and intermediate-ionization phases with values ${13\lesssim \log (n({{{\rm h}\,\rm{\small i}}})/{\rm cm}^{-2})\lesssim 20}$ and -3 ≲ log (z/z⊙) ≲ 1. comparing these properties to the galaxy properties, we infer a wide range of gaseous environments, including metal-rich outflows, metal-poor igm accretion, and tidal streams from galaxy-galaxy interactions. this diversity of structures forms the intragroup medium around a complex compact group environment at the epoch of peak star formation activity. surveys of low-redshift compact groups would benefit from obtaining a more complete census of this medium for characterizing evolutionary pathways. | a complex multiphase dla associated with a compact group at z = 2.431 traces accretion, outflows, and tidal streams |
we present a new catalogue of damped lyman-α absorbers from sdss dr16q, as well as new estimates of their statistical properties. our estimates are computed with the gaussian process models presented in garnett et al., ho, bird & garnett with an improved model for marginalizing uncertainty in the mean optical depth of each quasar. we compute the column density distribution function (cddf) at 2 < z < 5, the line density (dn/dx), and the neutral hydrogen density (ωdla). our gaussian process model provides a posterior probability distribution of the number of dlas per spectrum, thus allowing unbiased probabilistic predictions of the statistics of dla populations even with the noisiest data. we measure a non-zero column density distribution function for $n_{\rm {hi}}\lt 3 \times 10^{22} \, \rm {cm}^{-2}$ with $95{{\ \rm per\ cent}}$ confidence limits, and $n_{\rm {hi}}\lesssim 10^{22} \, \rm {cm}^{-2}$ for spectra with signal-to-noise ratios >4. our results for dla line density and total hydrogen density are consistent with previous measurements. despite a small bias due to the poorly measured blue edges of the spectra, we demonstrate that our new model can measure the dla population statistics when the dla is in the lyman-β forest region. we verify our results are not sensitive to the signal-to-noise ratios and redshifts of the background quasars although a residual correlation remains for detections from zqso < 2.5, indicating some residual systematics when applying our models on very short spectra, where the sdss spectral observing window only covers part of the lyman-α forest. | damped lyman-α absorbers from sloan digital sky survey dr16q with gaussian processes |
central supermassive black holes of active galactic nuclei host hot plasma with a temperature of 109 k, namely coronae. like the sun, black hole coronae are theoretically believed to be heated by their magnetic activity, which have not been observed yet. here we report the detection of coronal radio synchrotron emission from two nearby seyfert galaxies using the atacama large millimeter/submillimeter array, the karl g. jansky very large array, and australia telescope compact array. the coronal magnetic field of both systems is estimated to be ∼10 g on scales of ∼40 schwarzschild radii from the central black holes. this magnetic field strength is weaker than the prediction from the magnetically heated corona scenario. we also find that coronae of seyferts are composed of both thermal and nonthermal electrons. this may imply a possible contribution of seyferts to the cosmic mev gamma-ray background radiation. | detection of coronal magnetic activity in nearby active supermassive black holes |
we analyze multi-unit spectroscopic explorer observations of nine low-redshift (z < 0.1) palomar-green quasar host galaxies to investigate the spatial distribution and kinematics of the warm, ionized interstellar medium, with the goal of searching for and constraining the efficiency of active galactic nucleus (agn) feedback. after separating the bright agn from the starlight and nebular emission, we use pixel-wise, kpc-scale diagnostics to determine the underlying excitation mechanism of the line emission, and we measure the kinematics of the narrow-line region (nlr) to estimate the physical properties of the ionized outflows. the radial size of the nlr correlates with the agn luminosity, reaching scales of ~5 kpc and beyond. the geometry of the nlr is well-represented by a projected biconical structure, suggesting that the agn radiation preferably escapes through the ionization cone. we find enhanced velocity dispersions (≳100 km s-1) traced by the hα emission line in localized zones within the ionization cones. interpreting these kinematic features as signatures of interaction between an agn-driven ionized gas outflow and the host galaxy interstellar medium, we derive mass-outflow rates of ~0.008-1.6 m ⊙ yr-1 and kinetic injection rates of ~1039-1042 erg s-1, which yield extremely low coupling efficiencies of ≲10-3. these findings add to the growing body of recent observational evidence that agn feedback is highly ineffective in the host galaxies of nearby agns. | ionized outflows in nearby quasars are poorly coupled to their host galaxies |
gravity+ is the upgrade for gravity and the very large telescope interferometer (vlti) with wide-separation fringe tracking, new adaptive optics, and laser guide stars on all four 8 m unit telescopes (uts) to enable ever-fainter, all-sky, high-contrast, milliarcsecond interferometry. here we present the design and first results of the first phase of gravity+, known as gravity wide. gravity wide combines the dual-beam capabilities of the vlti and the gravity instrument to increase the maximum separation between the science target and the reference star from 2 arcseconds with the 8 m uts up to several 10 arcseconds, limited only by the earth's turbulent atmosphere. this increases the sky-coverage of gravity by two orders of magnitude, opening up milliarcsecond resolution observations of faint objects and, in particular, the extragalactic sky. the first observations in 2019-2022 include the first infrared interferometry of two redshift z ~ 2 quasars, interferometric imaging of the binary system hd 105913a, and repeat observations of multiple star systems in the orion trapezium cluster. we find the coherence loss between the science object and fringe-tracking reference star well described by the turbulence of the earth's atmosphere. we confirm that the larger apertures of the uts result in higher visibilities for a given separation due to the broader overlap of the projected pupils on the sky and provide predictions for visibility loss as a function of separation to be used for future planning. | first light for gravity wide. large separation fringe tracking for the very large telescope interferometer |
we report on the observations of the quasar nrao 530 with the event horizon telescope (eht) on 2017 april 5-7, when nrao 530 was used as a calibrator for the eht observations of sagittarius a*. at z = 0.902, this is the most distant object imaged by the eht so far. we reconstruct the first images of the source at 230 ghz, at an unprecedented angular resolution of ~20 μas, both in total intensity and in linear polarization (lp). we do not detect source variability, allowing us to represent the whole data set with static images. the images reveal a bright feature located on the southern end of the jet, which we associate with the core. the feature is linearly polarized, with a fractional polarization of ~5%-8%, and it has a substructure consisting of two components. their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. the jet extends over 60 μas along a position angle ~ -28°. it includes two features with orthogonal directions of polarization (electric vector position angle), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet. the outermost feature has a particularly high degree of lp, suggestive of a nearly uniform magnetic field. future eht observations will probe the variability of the jet structure on microarcsecond scales, while simultaneous multiwavelength monitoring will provide insight into the high-energy emission origin. | the event horizon telescope image of the quasar nrao 530 |
we present data releases 4 and 5 of the quasar catalog from the quasar survey by the large sky area multi-object fiber spectroscopic telescope (lamost), which includes quasars observed between 2015 september and 2017 june. there are a total of 19,253 quasars identified by visual inspections of the spectra. among them, 11,458 were independently discovered by lamost, in which 3296 were reported by the sdss dr12 and dr14 quasar catalog after our survey began, while the remaining 8162 are new discoveries of lamost. we provide the emission line measurements for hα, hβ, mg ii, and/or c iv for 18,100 quasars. since lamost does not have absolute flux calibration information, we obtain the monochromatic continuum luminosities by fitting the sdss photometric data using the quasar spectra, and then estimate the black hole masses. the catalog and spectra for these quasars are available online. this is the third installment in the series of lamost quasar surveys that has released spectra for ∼43,000 quasars to date. there are 24,772 independently discovered quasars, 17,128 of which are newly discovered. in addition to this great supplement to the new quasar discoveries, lamost has also provided a large database (overlapped with sdss) for investigating quasar spectral variability and discovering unusual quasars, including changing-look quasars, with ongoing and upcoming large surveys. | the large sky area multi-object fiber spectroscopic telescope (lamost) quasar survey: the fourth and fifth data releases |
gravitational-waves (gws) data have widely been used for testing preferred modified gravity theories. in this paper, we investigate the possibility of testing them in the strong gravity regime by looking at the properties of compact objects in dense matter physics. in this direction modified gravity theories such as f(r, t) gravity can be tested with the recently discovered compact binary merger, gw 190814, containing a compact object with mass 2.50-2.67 m⊙. by considering these constraints on maximum mass of such an object, we predict the existence of quark stars (qss) made of quark matter in the color-flavor-locked (cfl) phase of color superconductivity. such a state is significantly more bound than ordinary quark matter and enhances the possibility of the existence of a pure stable qs. we focus on the following aspects in particular: mass-radius profile, mass-central mass density relation, compactness and the corresponding effective adiabatic index for stability related issues. our result implies that predicted properties for qss are well consistent with gw 190814 observational data that helps us to impose constraints on the theoretical models of dense nuclear matter. | constraints on the maximum mass of quark star and the gw 190814 event |
observed at z = 4.601 and with lbol = 3.5 × 1014 l⊙ , w2246-0526 is the most luminous galaxy known in the universe and hosts a deeply buried active galactic nucleus (agn)/supermassive black hole (smbh). discovered using the wide-field infrared survey explorer, w2246-0526 is classified as a hot dust-obscured galaxy, based on its luminosity and dust temperature. here, we present spatially resolved alma [c ii]157.7 μm observations of w2246-0526, providing unique insight into the kinematics of its interstellar medium (ism). the measured [c ii] -to-far-infrared ratio is ∼ 2 × 10-4, implying ism conditions that compare only with the most obscured, compact starbursts and agns in the local universe today. the spatially resolved [c ii] line is strikingly uniform and very broad, 500-600 km s-1 wide, extending throughout the entire galaxy over about 2.5 kpc, with modest shear. such a large, homogeneous velocity dispersion indicates a highly turbulent medium. w2246-0526 is unstable in terms of the energy and momentum that are being injected into the ism, strongly suggesting that the gas is being blown away from the system isotropically, likely reflecting a cathartic state on its road to becoming an unobscured quasar. w2246-0526 provides an extraordinary laboratory to study and model the properties and kinematics of gas in an extreme environment under strong feedback, at a time when the universe was 1/10 of its current age: a system pushing the limits that can be reached during galaxy formation. | the strikingly uniform, highly turbulent interstellar medium of the most luminous galaxy in the universe |
aims: the standard active galactic nuclei (agn)-galaxy co-evolutionary scenario predicts a phase of deeply "buried" supermassive black hole growth coexisting with a starburst (sb) before feedback phenomena deplete the cold molecular gas reservoir of the galaxy and an optically luminous quasar (qso) is revealed (called the sb-qso evolutionary sequence). the aim of this work is to measure the cold gas reservoir of three highly obscured qsos to test if their gas fraction is similar to that of submillimetre galaxies (smgs), as expected by some models, and to place these measurements in the context of the sb-qso framework.methods: we target co(1-0) transition in bzk4892, a compton thick (ct) qso at z = 2.6, co(1-0) in bzk8608 and co(2-1) in cdf153, two highly obscured (nh ≈ 6 × 1023 cm-2) qsos at z = 2.5 and z = 1.5, respectively. for these targets, we place 3σ upper limits on the co lines, with l'co < (1.5 ÷ 2.8)×1010 k km s-1 pc2. we also compare the molecular gas conditions of our targets with those of other systems at z > 1, considering normal star-forming galaxies and smgs, and unobscured and obscured agn from the literature. for the agn samples, we provide an updated and almost complete collection of targets with co follow-up at z > 1.results: bzk4892 displays a high star formation efficiency (sfe = lir/l'co > 410 l⊙/(k km s-1 pc2 )) and a gas fraction fgas = mgas/(mstar + mgas)< 10%. less stringent constraints are derived for the other two targets (fgas < 0.5 and sfe > 10 l⊙/(k km s-1 pc2 )). from the comparison with the literature data we found that, on average, i) obscured agn at z > 1 are associated with higher sfe and lower fgas with respect to normal star-forming galaxies and smgs; ii) mildly and highly obscured active galaxies have comparable gas fractions; iii) the sfe of ct and obscured agn are similar to those of unobscured agn.conclusions: within the sb-qso framework, these findings could be consistent with a scenario where feedback can impact the host galaxy already from the early phases of the sb-qso evolutionary sequence. | molecular gas content in obscured agn at z > 1 |
we present alma observations of the co(6-5) and [cii] emission lines and the sub-millimeter continuum of the z ∼ 6 quasi-stellar object (qso) sdss j231038.88+185519.7. compared to previous studies, we have analyzed a synthetic beam that is ten times smaller in angular size, we have achieved ten times better sensitivity in the co(6-5) line, and two and half times better sensitivity in the [cii] line, enabling us to resolve the molecular gas emission. we obtain a size of the dense molecular gas of 2.9 ± 0.5 kpc, and of 1.4 ± 0.2 kpc for the 91.5 ghz dust continuum. by assuming that co(6-5) is thermalized, and by adopting a co to h2 conversion factor αco = 0.8 m⊙k-1 (km s)-1 pc2, we infer a molecular gas mass of m(h2) = (3.2±0.2)×1010 m⊙. assuming that the observed co velocity gradient is due to an inclined rotating disk, we derive a dynamical mass of mdynsin2(i)=(2.4 ± 0.5)×1010 m⊙, which is a factor of approximately two smaller than the previously reported estimate based on [cii]. regarding the central black hole, we provide a new estimate of the black hole mass based on the c iv emission line detected in the vlt/x-shooter spectrum: mbh = (1.8 ± 0.5)×109 m⊙. we find a molecular gas fraction of μ = m(h2)/m* ∼ 4.4, where m∗ ≈ mdyn - m(h2) - m(bh). we derive a ratio νrot/σ ≈ 1 - 2 suggesting high gas turbulence, outflows/inflows and/or complex kinematics due to a merger event. we estimate a global toomre parameter q ∼ 0.2 - 0.5, indicating likely cloud fragmentation. we compare, at the same angular resolution, the co(6-5) and [cii] distributions, finding that dense molecular gas is more centrally concentrated with respect to [cii]. we find that the current bh growth rate is similar to that of its host galaxy. the reduced data cubes and images are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/619/a39 | the dense molecular gas in the z ∼ 6 qso sdss j231038.88+185519.7 resolved by alma |
theoretical models for the expected merger rates of intermediate-mass black holes (imbhs) are vital for planned gravitational-wave detection experiments such as the laser interferometer space antenna (lisa). using collisionless n-body simulations of dwarf galaxy (dg) mergers, we examine how the orbital decay of imbhs and the efficiency of imbh binary formation depend on the central dark matter (dm) density profile of the merging dgs. specifically, we explore various asymptotic inner slopes γ of the dg’s dm density distribution, ranging from steep cusps (γ = 1) to shallower density profiles (γ < 1), motivated by well-known baryonic-feedback effects as well as by dm models that differ from cold dm at the scales of dgs. we find that the inner dm slope is crucial for the formation (or lack thereof) of an imbh binary; only mergers between dgs with cuspy dm profiles (γ = 1) are favorable to forming a hard imbh binary, whereas when γ < 1 the imbhs stall at a separation of 50-100 pc. consequently, the rate of lisa signals from imbh coalescence will be determined by the fraction of dgs with a cuspy dm profile. conversely, the lisa event rates at imbh mass scales offer in principle a novel way to place constraints on the inner structure of dm halos in dgs and address the core-cusp controversy. we also show that, with spatial resolutions of ∼0.1 kpc, as often adopted in cosmological simulations, all imbhs stall, independent of γ. this suggests caution should be taken when employing cosmological simulations of galaxy formation to study bh dynamics in dgs. | formation of lisa black hole binaries in merging dwarf galaxies: the imprint of dark matter |
we present new multi unit spectroscopic explorer observations of quasar field q2131-1207 with a log n(h i} = 19.50 ± 0.15 sub-damped lyman α at zabs = 0.42980. we detect four galaxies at a redshift consistent with that of the absorber where only one was known before this study. two of these are star-forming galaxies, while the ones further away from the quasar (>140 kpc) are passive galaxies. we report the metallicities of the h ii regions of the closest objects (12 + log(o/h) = 8.98 ± 0.02 and 8.32 ± 0.16) to be higher or equivalent within the errors to the metallicity measured in absorption in the neutral phase of the gas (8.15 ± 0.20). for the closest object, a detailed morphokinematic analysis indicates that it is an inclined large rotating disc with vmax = 200 ± 3 km s-1. we measure the masses to be mdyn = 7.4 ± 0.4 × 1010 m⊙ and mhalo = 2.9 ± 0.2 × 1012 m⊙. some of the gas seen in absorption is likely to be corotating with the halo of that object, possibly due to a warped disc. the azimuthal angle between the quasar line-of-sight and the projected major axis of the galaxy on the sky is 12° ± 1° which indicates that some other fraction of the absorbing gas might be associated with accreting gas. this is further supported by the galaxy to gas metallicity difference. based on the same arguments, we exclude outflows as a possibility to explain the gas in absorption. the four galaxies form a large structure (at least 200 kpc wide) consistent with a filament or a galaxy group so that a fraction of the absorption could be related to intragroup gas. | nature of the absorbing gas associated with a galaxy group at z∼0.4 |
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