arXiv subjects

C. C. Steidel

Publications and source records attributed to C. C. Steidel.

At least 37 records · Page 2Linked to original sources

arXiv2010

Excess AGN Activity in the z=2.30 Protocluster in HS 1700+64

We present the results of spectroscopic, narrow-band and X-ray observations of a z=2.30 protocluster in the field of the QSO HS 1700+643. Using a sample of BX/MD galaxies, which are selected to be at z~2.2-2.7 by their rest-frame ultraviolet colours, we find that there are 5 protocluster AGN which have been identified by characteristic emission-lines in their optical/near-IR spectra; this represents an enhancement over the field significant at ~98.5 per cent confidence. Using a ~200 ks Chandra/ACIS-I observation of this field we detect a total of 161 X-ray point sources to a Poissonian false-probability limit of 4x10^{-6} and identify 8 of these with BX/MD galaxies. Two of these are spectroscopically confirmed protocluster members and are also classified as emission-line AGN. When compared to a similarly selected field sample the analysis indicates this is also evidence for an enhancement of X-ray selected BX/MD AGN over the field, significant at ~99 per cent confidence. Deep Lya narrow-band imaging reveals that a total of 4/123 Lya emitters (LAEs) are found to be associated with X-ray sources, with two of these confirmed protocluster members and one highly likely member. We do not find a significant enhancement of AGN activity in this LAE sample over that of the field (result significant at only 87 per cent confidence). The X-ray emitting AGN fractions for the BX/MD and LAE samples are found to be 6.9_{-4.4}^{+9.2} and 2.9_{-1.6}^{+2.9} per cent, respectively, for protocluster AGN with L_{2-10 keV}>4.6x10^{43} erg s^{-1} at z=2.30. These findings are similar to results from the z=3.09 protocluster in the SSA 22 field found by Lehmer et al. (2009), in that both suggest AGN activity is favoured in dense environments at z>2.

astro-ph.CO↗

arXiv2009

Halo Gas and Galaxy Disk Kinematics Derived from Observations and LCDM Simulations of MgII Absorption Selected Galaxies at Intermediate Redshift

We obtained ESI/Keck rotation curves of 10 MgII absorption selected galaxies (0.3 < z < 1.0) for which we have WFPC-2/HST images and high resolution HIRES/Keck and UVES/VLT quasar spectra of the MgII absorption profiles. We perform a kinematic comparison of these galaxies and their associated halo MgII absorption. For all 10 galaxies, the majority of the absorption velocities lie in the range of the observed galaxy rotation velocities. In 7/10 cases, the absorption velocities reside fully to one side of the galaxy systemic velocity and usually align with one arm of the rotation curve. In all cases, a constant rotating thick-disk model poorly reproduces the full spread of observed MgII absorption velocities when reasonably realistic parameters are employed. In 2/10 cases, the galaxy kinematics, star formation surface densities, and absorption kinematics have a resemblance to those of high redshift galaxies showing strong outflows. We find that MgII absorption velocity spread and optical depth distribution may be dependent on galaxy inclination. To further aid in the spatial-kinematic relationships of the data, we apply quasar absorption line techniques to a galaxy (v_c=180 km/s) embedded in LCDM simulations. In the simulations, MgII absorption selects metal enriched "halo" gas out to roughly 100 kpc from the galaxy, tidal streams, filaments, and small satellite galaxies. Within the limitations inherent in the simulations, the majority of the simulated MgII absorption arises in the filaments and tidal streams and is infalling towards the galaxy with velocities between -200 < v_r < -180 km/s. The MgII absorption velocity offset distribution (relative to the simulated galaxy) spans ~200 km/s with the lowest frequency of detecting MgII at the galaxy systematic velocity.

astro-ph.CO↗

arXiv2009

The SINS survey: SINFONI Integral Field Spectroscopy of z ~ 2 Star-forming Galaxies

We present the SINS survey with SINFONI of high redshift galaxies. With 80 objects observed and 63 detected, SINS is the largest survey of spatially resolved gas kinematics, morphologies, and physical properties of star-forming galaxies at z~1-3. We describe the selection of the targets, the observations, and the data reduction. We then focus on the "SINS Halpha sample" of 62 rest-UV/optically-selected sources at 1.3 ~10 star-forming galaxies at z~1.5-2.5, with some bias towards bluer systems compared to pure K-selected samples due to the requirement of secure optical redshift. The sample spans two orders of magnitude in stellar mass and in absolute and specific star formation rates, with median values of approximately log(M*/Msun) = 10.5, 70 Msun/yr, and 3/Gyr. The ionized gas distribution and kinematics are spatially resolved on scales ranging from 1.5 kpc for adaptive optics assisted observations to typically 4-5 kpc for seeing-limited data. The Halpha morphologies tend to be irregular and/or clumpy. About one-third are rotation-dominated yet turbulent disks, another third comprises compact and velocity dispersion-dominated objects, and the remaining galaxies are clear interacting/merging systems; the fraction of rotation-dominated systems increases among the more massive part of the sample. The Halpha luminosities and equivalent widths suggest on average roughly twice higher dust attenuation towards the HII regions relative to the bulk of the stars, and comparable current and past-averaged star formation rates. [Abridged]

astro-ph.CO↗

arXiv2009

The evolution of the hard X-ray luminosity function of AGN

We present new observational determinations of the evolution of the 2-10keV X-ray luminosity function (XLF) of AGN. We utilise data from a number of surveys including both the 2Ms Chandra Deep Fields and the AEGIS-X 200ks survey, enabling accurate measurements of the evolution of the faint end of the XLF. We combine direct, hard X-ray selection and spectroscopic follow-up or photometric redshift estimates at z<1.2 with a rest-frame UV colour pre-selection approach at higher redshifts to avoid biases associated with catastrophic failure of the photometric redshifts. Only robust optical counterparts to X-ray sources are considered using a likelihood ratio matching technique. A Bayesian methodology is developed that considers redshift probability distributions, incorporates selection functions for our high redshift samples, and allows robust comparison of different evolutionary models. We find that the XLF retains the same shape at all redshifts, but undergoes strong luminosity evolution out to z~1, and an overall negative density evolution with increasing redshift, which thus dominates the evolution at earlier times. We do not find evidence that a Luminosity-Dependent Density Evolution, and the associated flattening of the faint-end slope, is required to describe the evolution of the XLF. We find significantly higher space densities of low-luminosity, high-redshift AGN than in prior studies, and a smaller shift in the peak of the number density to lower redshifts with decreasing luminosity. The total luminosity density of AGN peaks at z=1.2+/-0.1, but there is a mild decline to higher redshifts. We find >50% of black hole growth takes place at z>1, with around half in Lx<10^44 erg/s AGN.

astro-ph.CO↗

arXiv2009

The SINS survey: modeling the dynamics of z~2 galaxies and the high-z Tully-Fisher relation

We present the modeling of SINFONI integral field dynamics of 18 star forming galaxies at z ~ 2 from Halpha line emission. The galaxies are selected from the larger sample of the SINS survey, based on the prominence of ordered rotational motions with respect to more complex merger induced dynamics. The quality of the data allows us to carefully select systems with kinematics dominated by rotation, and to model the gas dynamics across the whole galaxy using suitable exponential disk models. We obtain a good correlation between the dynamical mass and the stellar mass, finding that large gas fractions Mgas~M*) are required to explain the difference between the two quantities. We use the derived stellar mass and maximum rotational velocity Vmax from the modeling to construct for the first time the stellar mass Tully-Fisher relation at z ~ 2.2. The relation obtained shows a slope similar to what is observed at lower redshift, but we detect an evolution of the zero point. We find that at z ~ 2.2 there is an offset in log(M*) for a given rotational velocity of 0.41+-0.11 with respect to the local Universe. This result is consistent with the predictions of the latest N-body/hydrodynamical simulations of disk formation and evolution, which invoke gas accretion onto the forming disk in filaments and cooling flows. This scenario is in agreement with other dynamical evidence from SINS, where gas accretion from the halo is required to reproduce the observed properties of a large fraction of the z ~ 2 galaxies.

astro-ph.CO↗

arXiv2008

From rings to bulges: evidence for rapid secular galaxy evolution at z~2 from integral field spectroscopy in the SINS survey

We present Ha integral field spectroscopy of well resolved, UV/optically selected z~2 star-forming galaxies as part of the SINS survey with SINFONI on the ESO VLT. Our laser guide star adaptive optics and good seeing data show the presence of turbulent rotating star forming rings/disks, plus central bulge/inner disk components, whose mass fractions relative to total dynamical mass appears to scale with [NII]/Ha flux ratio and star formation age. We propose that the buildup of the central disks and bulges of massive galaxies at z~2 can be driven by the early secular evolution of gas-rich proto-disks. High redshift disks exhibit large random motions. This turbulence may in part be stirred up by the release of gravitational energy in the rapid cold accretion flows along the filaments of the cosmic web. As a result dynamical friction and viscous processes proceed on a time scale of <1 Gyr, at least an order of magnitude faster than in z~0 disk galaxies. Early secular evolution thus drives gas and stars into the central regions and can build up exponential disks and massive bulges, even without major mergers. Secular evolution along with increased efficiency of star formation at high surface densities may also help to account for the short time scales of the stellar buildup observed in massive galaxies at z~2.

astro-ph↗

arXiv2008

Halo Gas Cross Sections And Covering Fractions of MgII Absorption Selected Galaxies

We examine halo gas cross sections and covering fractions, f_c, of intermediate redshift MgII absorption selected galaxies. We computed statistical absorber halo radii, R_x, using current values of dN/dz and Schechter luminosity function parameters, and have compared these values to the distribution of impact parameters and luminosities from a sample of 37 galaxies. For equivalent widths W_r(2796) > 0.3 Ang, we find 43 < R_x < 88 kpc, depending on the lower luminosity cutoff and the slope, beta, of the Holmberg-like luminosity scaling, R \propto L^beta. The observed distribution of impact parameters, D, are such that several absorbing galaxies lie at D > R_x and several non-absorbing galaxies lie at D < R_x. We deduced f_c must be less than unity and obtain a mean of ~ 0.5 for our sample. Moreover, the data suggest halo radii of MgII absorbing galaxies do not follow a luminosity scaling with beta in the range of 0.2-0.28, if f_c= 1 as previously reported. However, provided f_c~0.5, we find that halo radii can remain consistent with a Holmberg-like luminosity relation with beta ~ 0.2 and R* = R_x/sqrt(f_c)= 110 kpc. No luminosity scaling (beta=0) is also consistent with the observed distribution of impact parameters if f_c < 0.37. The data support a scenario in which gaseous halos are patchy and likely have non-symmetric geometric distributions about the galaxies. We suggest halo gas distributions may not be govern primarily by galaxy mass/luminosity but also by stochastic processes local to the galaxy.

astro-ph↗

arXiv2007

Detection of the Transverse Proximity Effect: Radiative Feedback from Bright QSOs

Measuring the response of the intergalactic medium to a blast of ionizing radiation allows one to infer the physical properties of the medium and, in principle, the lifetime and isotropy of the radiating source. The most sensitive such measurements can be made if the source of radiation is near the line of sight to a bright background QSO. We present results based on deep Keck/HIRES observations of the QSO triplet KP76, KP77 and KP78 at z ~2.5, with separations of 2-3 arcmin on the plane of the sky. Using accurate systemic redshifts of the QSOs from near-IR spectroscopy, we quantify the state of the IGM gas in the proximity regions where the expected ionizing flux from the foreground QSOs exceeds that of the metagalactic background by factors of 10-200, assuming constant and isotropic emission. Based on the unusual ionization properties of the absorption systems with detected HI, CIV, and OVI, we conclude that the gas has been significantly affected by the UV radiation from the nearby QSOs. Aided by observations of the galaxy density near the foreground QSOs, we discuss several effects that may explain why the transverse proximity effect has eluded most previous attempts to detect it. Our observations suggest that the luminosities of KP76 and KP77 have remained comparable to current values over timescales of, respectively, Delta t > 25 Myr and 16 Myr < Delta t < 33 Myr - consistent with typical QSO lifetimes estimated from independent, less-direct methods. There is no evidence that the UV radiation from either QSO was significantly anisotropic during these intervals.

astro-ph↗

arXiv2007

Connecting Galaxy Disk and Extended Halo Gas Kinematics

We have explored the galaxy disk/extended halo gas kinematic relationship using rotation curves (Keck/ESI) of ten intermediate redshift galaxies which were selected by MgII halo gas absorption observed in quasar spectra. Previous results of six edge-on galaxies, probed along their major axis, suggest that observed halo gas velocities are consistent with extended disk-like halo rotation at galactocentric distances of 25-72 kpc. Using our new sample, we demonstrate that the gas velocities are by and large not consistent with being directly coupled to the galaxy kinematics. Thus, mechanisms other than co-rotation dynamics (i.e., gas inflow, feedback, galaxy-galaxy interactions, etc.) must be invoked to account for the overall observed kinematics of the halo gas. In order to better understand the dynamic interaction of the galaxy/halo/cosmic web environment, we performed similar mock observations of galaxies and gaseous halos in Lambda-CDM cosmological simulations. We discuss an example case of a z=0.92 galaxy with various orientations probing halo gas at a range of positions. The gas dynamics inferred using simulated quasar absorption lines are consistent with observational data.

astro-ph↗

arXiv2007

Dynamical Properties of z~2 Star Forming Galaxies and a Universal Star Formation Relation

We present the first comparison of the dynamical properties of different samples of z~1.4-3.4 star forming galaxies from spatially resolved imaging spectroscopy from SINFONI/VLT integral field spectroscopy and IRAM CO millimeter interferometry. Our samples include 16 rest-frame UV-selected, 16 rest-frame optically-selected and 13 submillimeter galaxies (SMGs). We find that restframe UV- and optically bright (K<20) z~2 star forming galaxies are dynamically similar, and follow the same velocity-size relation as disk galaxies at z~0. In the theoretical framework of rotating disks forming from dissipative collapse in dark matter halos, the two samples require a spin parameter ranging from 0.06 to 0.2. In contrast bright SMGs have larger velocity widths and are much more compact. Hence, SMGs have lower angular momenta and higher matter densities than either of the UV- or optically selected populations. This indicates that dissipative major mergers may dominate the SMGs population, resulting in early spheroids, and that the majority of UV/optically bright galaxies have evolved less violently [...]. These early disks may later evolve into spheroids via disk instabilities or mergers. Because of their small sizes and large densities, SMGs lie at the high surface density end of a universal (out to z=2.5) "Schmidt-Kennicutt" relation between gas surface density and star formation rate surface density with a slope of ~1.7.

astro-ph↗

arXiv2006

Integral Field Spectroscopy of a Candidate Disk Galaxy at z~1.5 using Laser Guide Star Adaptive Optics

We present 0.1" resolution near-infrared integral field spectroscopy of Halpha in a z=1.4781 star forming galaxy, Q2343-BM133. These observations were obtained with OSIRIS (OH Suppressing Infra-Red Imaging Spectrograph) using the W.M. Keck Observatory Laser Guide Star Adaptive Optics system. Halpha emission is resolved over a 0.8" (6.8 kpc) x 0.5" (4.3 kpc) region with a 0.1" spatial resolution. We find a global flux of 4.2+/-0.6x10^{-16} ergs s^{-1} cm^{-2}, and detect a spatially resolved velocity gradient of ~134 km s^{-1} across the galaxy and a global velocity dispersion of 73+/-9 km s^{-1}. An upper limit of NII/Halpha < 0.12 is inferred, which implies that this galaxy is not dominated by an active galactic nucleus and has a metallicity at or below 1/2 solar metallicity. We derive a star formation rate (SFR) of 47+/-6 Msun yr^{-1}, and a dereddened SFR of 66+/-9 Msun yr^{-1}. Two-dimensional kinematics for Q2343-BM133 fit well with an inclined-disk model, with which we estimate an enclosed mass of 4.3x10^{9} Msun within 5.5 kpc. A possible merger scenario is also presented, and can not be fully ruled out. We derive a virial mass of 1.1x10^{10} Msun for a disk geometry, using the observed velocity dispersion. We propose that Q2343-BM133 is currently at an early stage of disk formation at a look-back time of 9.3 Gyr.

astro-ph↗

arXiv2006

The X-ray emission of Lyman break galaxies

We present an analysis of the X-ray emission of a large sample of z~3 Lyman break galaxies (LBGs), based on Chandra/ACIS observations of several LBG survey fields. 24 LBGs are directly detected in the X-ray. 13 of the LBGs have optical spectroscopic signatures of AGN activity, but almost all the other X-ray detections are also likely to host an accreting black hole based on their X-ray properties. The AGN exhibit a wide range in X-ray luminosity, from weak Seyferts to bright QSOs. Optical spectroscopy identified approximately 1/3 of the X-ray detected sources as broad line QSOs, 1/3 as narrow line AGN and 1/3 as normal star forming LBGs. The fraction of X-ray detected LBGs is 3%, much lower than has been found for submm selected galaxies. 2 galaxies have X-ray luminosities, spectra and f_x/f_opt values that are consistent with emission from star formation processes and are candidate X-ray bright, pure starburst galaxies at z~3. X-ray spectral analysis of the LBGs shows a mean photon index 1.96, similar to local AGN. There is evidence for absorption in at least 40% of the objects. Significantly more absorption is evident in the narrow line AGN, consistent with AGN unification schemes. After correction for absorption the narrow and broad line objects show the same average luminosity. LBGs spectroscopically classified as normal galaxies are less luminous in X-ray indicating that the host galaxy is outshining any optical AGN signature. For the LBGs without direct detections, stacking the X-ray flux in the 2 deepest fields under consideration (the HDF-N and GWS) produced significant detections in each. The detection in the HDF-N gives an X-ray derived SFR of 42.4+/-7.8 Msolar/yr per LBG and, by comparing with the UV SFR, the implied UV extinction correction is 4.1+/-0.8. (abridged)

astro-ph↗

arXiv2006

The Deep Chandra Survey of the Groth Strip - II. optical identification of the X-ray sources

We discuss the optical and X-ray spectral properties of the sources detected in a single 200ks Chandra pointing in the Groth-Westphal Strip region. Optical identifications and spectroscopic redshifts are primarily from the DEEP2 survey. This is complemented with deeper (r~26mag) multi-waveband data (ugriz) from the Canada France Hawaii Legacy Survey to estimate photometric redshifts and to optically identify sources fainter than the DEEP2 magnitude limit (R(AB)~24.5mag). We focus our study on the 2-10keV selected sample comprising 97 sources to the limit ~8e-16erg/s/cm2, this being the most complete in terms of optical identification rate (86%) and redshift determination fraction (63%; both spectroscopic and photometric). We first construct the redshift distribution of the sample which shows a peak at z~1. This is in broad agreement with models where less luminous AGNs evolve out to z~1 with powerful QSOs peaking at higher redshift, z~2. Evolution similar to that of broad-line QSOs applied to the entire AGN population (both type-I and II) does not fit the data. We also explore the observed N_H distribution of the sample and estimate a fraction of obscured AGN (N_H>1e22) of ~48%. This is found to be consistent with both a luminosity dependent intrinsic N_H distribution, where less luminous systems comprise a higher fraction of type-II AGNs, and models with a fixed ratio 2:1 between type-I and II AGNs. We further compare our results with those obtained in deeper and shallower surveys. We argue that a luminosity dependent parametrisation of the intrinsic N_H distribution is required to account for the fraction of obscured AGN observed in different samples over a wide range of fluxes.

astro-ph↗

arXiv2006

SINFONI Integral Field Spectroscopy of z~2 UV-selected Galaxies: Rotation Curves and Dynamical Evolution

We present 0.5" resolution near-IR integral field spectroscopy of the Ha line emission of 14 z~2 UV-selected BM/BX galaxies obtained with SINFONI at ESO/VLT. The mean Ha half-light radius r_1/2 is about 4kpc and line emission is detected over > ~20kpc in several sources. In 9 sources, we detect spatially-resolved velocity gradients, from 40 to 410 km/s over ~10kpc. The observed kinematics of the larger systems are consistent with orbital motions. Four galaxies are well described by rotating disks with clumpy morphologies and we extract rotation curves out to radii > ~10kpc. One or two galaxies exhibit signatures more consistent with mergers. Analyzing all 14 galaxies in the framework of rotating disks, we infer mean inclination- and beam-corrected maximum circular velocities v_c of 180+-90 km/s and dynamical masses of (0.5-25)x10^10 Msun within r_1/2. On average, the dynamical masses are consistent with photometric stellar masses assuming a Chabrier/Kroupa IMF but too small for a 0.1-100 Msun Salpeter IMF. The specific angular momenta of our BM/BX galaxies are similar to those of local late-type galaxies. The specific angular momenta of their baryons are comparable to those of their dark matter halos. Extrapolating from the average v_c at 10kpc, the virial mass of the typical halo of a galaxy in our sample is 10^(11.7+-0.5) Msun. Kinematic modeling of the 3 best cases implies a ratio of v_c to local velocity dispersion of order 2-4 and accordingly a large geometric thickness. We argue that this suggests a mass accretion (alternatively, gas exhaustion) timescale of ~500Myr. We also argue that if our BM/BX galaxies were initially gas rich, their clumpy disks will subsequently lose their angular momentum and form compact bulges on a timescale of ~1 Gyr. [ABRIDGED]

astro-ph↗

arXiv2006

On the reliability of CIV 1549 as an abundance indicator for high redshift star-forming galaxies

We reconsider the use of the equivalent width of CIV 1549, EW(CIV), as an indicator of the oxygen abundance in star-forming galaxies, as proposed by Heckman et al. for nearby starbursts. We refine the local calibration of EW(CIV) vs. log (O/H) by using a restricted wavelength window which minimises blending with interstellar absorption lines. When applied to the stellar component only of the complex CIV 1549 features in two high redshift galaxies with good quality spectra, MS1512-cB58 (z = 2.7268) and Q1307-BM1163 (z = 1.4105), the local calibration gives values of the oxygen abundance which are in good agreement with other metallicity determinations based on nebular emission and interstellar absorption lines. Our main conclusion is that for this method to give reliable results at high redshifts, it should only be used on data of sufficiently high spectral resolution (R > 1000) for stellar and interstellar CIV components to be clearly separated. Oxygen abundances will be systematically overestimated if the local calibration is applied to spectra of high-z galaxies obtained with the low resolving powers (R ~ 200-300) of many current wide field surveys. It will also be necessary to understand better the causes of the scatter in the local relation, before we can be confident of inferences from it at high z.

astro-ph↗

arXiv2005

Spectroscopy of GRB 050505 at z=4.275: A logN(HI)=22.1 DLA Host Galaxy and the Nature of the Progenitor

We present the discovery of the optical afterglow of GRB 050505 and an optical absorption spectrum obtained with the Keck I 10-m telescope. The spectrum exhibits three redshifted absorption systems with the highest, at z=4.2748, arising in the GRB host galaxy. The host absorption system is marked by a damped Ly-alpha (DLA) feature with a neutral hydrogen column density of logN(HI)=22.05+/-0.10, higher than that of any QSO-DLA detected to date, but similar to several other recent measurements from GRB spectra. In addition, we detect absorption lines from both low- and high-ionization species from which we deduce a metallicity, Z~0.06 Z_solar, with a depletion pattern that is roughly similar to that of the Galactic warm halo, warm disk, or disk+halo. More importantly, we detect strong absorption from SiII* indicating a dense environment, n_H>10^2 cm^-3, in the vicinity of the burst, with a size of about 4 pc. In addition, the CIV absorption system spans a velocity range of about 1000 km/s, which is not detected in any other absorption feature. We show that the most likely interpretation for this wide velocity range is absorption in the wind from the progenitor star. In this context, the lack of corresponding SiIV absorption indicates that the progenitor had a mass of <25 M_solar and a metallicity <0.1 Z_solar, and therefore required a binary companion to eject its hydrogen envelope prior to the GRB explosion. Finally, by extending the GRB-DLA sample to z~4.3 we show that these objects appear to follow a similar metallicity-redshift relation as in QSO-DLAs, but with systematically higher metallicities. It remains to be seen whether this trend is simply due to the higher neutral hydrogen columns in GRB-DLAs, or if it is a manifestation of different star formation properties in GRB-DLAs. [abridged]

astro-ph↗

arXiv2005

Possible Detection of Lyman-alpha Fluorescence from a Damped Lyman Alpha system at Redshift z=2.8

We have detected Lyman-alpha emission from a damped Lyman-alpha system (DLA) that lies near the bright quasar HS1549+1919. The DLA has the same redshift as HS1549+1919 and was discovered in the spectrum of a faint QSO that lies 49" away (380 proper kpc). The emission line's luminosity, double-peaked profile, and small spatial separation from the DLA suggest that it may be fluorescent Lyman-alpha emission from gas that is absorbing the nearby QSO's radiation. If this is the case, our observations show that the DLA has a size of at least 1.5" and that the QSO's luminosity one million years ago was similar to its luminosity today. A survey for similar systems within 1' of bright QSOs would put interesting limits on the mean quasar lifetime.

astro-ph↗

arXiv2005

Constraints from Galaxy-AGN Clustering on the Correlation between Galaxy and Black Hole Mass at Redshifts 2<Z<3

We use the clustering of galaxies around distant active-galactic nuclei to derive an estimate of the relationship between galaxy and black hole mass that obtained during the ancient quasar epoch, at redshifts 2 <~ z <~ 3, when giant black holes accreted much of their mass. Neither the mean relationship nor its scatter differs significantly from what is observed in the local universe, at least over the ranges of apparent magnitude (16 <~ G_AB <~ 26) and black-hole mass (10^6 <~ M_BH/M_sun <~ 10^10.5) that we are able to probe.

astro-ph↗