Virial Mass Estimates Research Articles

Stripe 82X Data Release 3: Multiwavelength Catalog with New Spectroscopic Redshifts and Black Hole Masses

We present the third catalog release of the wide-area (31.3 deg2) Stripe 82 X-ray survey. This catalog combines previously published X-ray source properties with multiwavelength counterparts and photometric redshifts, presents 343 new spectroscopic redshifts, and provides black hole masses for 1297 Type 1 active galactic nuclei (AGN). With spectroscopic redshifts for 3457 out of 6181 Stripe 82X sources, the survey has a spectroscopic completeness of 56%. This completeness rises to 90% when considering the contiguous portions of the Stripe 82X survey with homogeneous X-ray coverage at an optical magnitude limit of r < 22. Within that portion of the survey, 23% of AGN can be considered obscured by being either a Type 2 AGN, reddened (R − K > 4, Vega), or X-ray obscured with a column density of N H > 1022 cm−2. Unlike other surveys, there is only an 18% overlap between Type 2 and X-ray obscured AGN. We calculated black hole masses for Type 1 AGN that have Sloan Digital Sky Survey spectra using virial mass estimators calibrated on the Hβ, Mg ii, Hα, and C iv emission lines. We find wide scatter in these black hole mass estimates, indicating that statistical analyses should use black hole masses calculated from the same formula to minimize bias. We find that the AGN with the highest X-ray luminosities are accreting at the highest Eddington ratios, consistent with the picture that most black hole mass accretion happens in the phase when the AGN is luminous (L 2−10keV > 1045 erg s−1).

X-Ray View of Little Red Dots: Do They Host Supermassive Black Holes?

The discovery of Little Red Dots (LRDs)—a population of compact, high-redshift, dust-reddened galaxies—is one of the most surprising results from JWST. However, the nature of LRDs is still debated: does the near-infrared emission originate from accreting supermassive black holes (SMBHs), or intense star formation? In this work, we utilize ultra-deep Chandra observations and study LRDs residing behind the lensing galaxy cluster, A2744. We probe the X-ray emission from individual galaxies but find that they remain undetected and provide SMBH mass upper limits of ≲(1.5–16) × 106 M ⊙ assuming Eddington limited accretion. To increase the signal-to-noise ratios, we conduct a stacking analysis of the full sample with a total lensed exposure time of ≈87 Ms. We also bin the galaxies based on their stellar mass, lensing magnification, and detected broad-line Hα emission. For the LRDs exhibiting broad-line Hα emission, there is a hint of a stacked signal (∼2.6σ), corresponding to an SMBH mass of ∼3.2 × 106 M ⊙. Assuming unobscured, Eddington-limited accretion, this black hole (BH) mass is at least 1.5 orders of magnitude lower than that inferred from virial mass estimates using JWST spectra. Given galaxy-dominated stellar mass estimates, our results imply that LRDs do not host overmassive SMBHs and/or accrete at a few percent of their Eddington limit. However, alternative stellar mass estimates may still support that LRDs host overmassive BHs. The significant discrepancy between the JWST and Chandra data hints that the scaling relations used to infer the SMBH mass from the Hα line and virial relations may not be applicable for high-redshift LRDs.

Effect of the Large Magellanic Cloud on the kinematics of Milky Way satellites and virial mass estimate

We present a study illustrating the effects of the passage of a Large Magellanic Cloud (LMC) mass satellite on the distance and velocity distributions of satellites in Λ+Cold Dark Matter simulations of Milky Way (MW) sized halos. In agreement with previous studies, we find that during such a passage the velocity distribution develops a high-velocity tail, which can bias velocity-based virial halo mass estimates. When the velocity distribution of MW satellites is corrected for effects of the LMC passage, it is consistent with the distributions in halos of masses as low as and as high as 1.5×1012M⊙. We present a new halo mass estimator , where c is the coefficient calibrated using satellite systems in the simulated MW-sized halos, is the variance of 3D velocities taken with the sign of the radial velocity of each satellite, and is the median halocentric distance of the satellites. We show that the estimator has only s=8% scatter around the median relation of the estimated and true halo masses and deviates by &lt;2s from the median during the pericentric passage of an LMC-like subhalo. This is because and deviate in the opposite directions during such passages. We apply the estimator to the MW satellite system and estimate the virial mass of the Milky Way of , in good agreement with several recent estimates using other methods.

Kinematical small-scale fluctuations do not affect the measurement of the dynamical mass of galaxies

ABSTRACT The stellar kinematics of low-mass galaxies are usually observed to be very unsmooth with significant kinematical fluctuations in small scales, which cannot be consistent with the projected centrosymmetric stellar kinematics obtained from commonly used dynamical models. In this work, we aim to test whether the high degree of kinematical fluctuations affects the dynamical mass estimate of galaxies. We use the asymmetry parameter η obtained from the 180° rotation self-subtraction of stellar kinematics of galaxies to quantify the degree of kinematical small-scale fluctuations. We use TNG50 numerical simulation to construct a large sample of mock galaxies with known total masses, and then obtained the virial dynamical mass estimator of these mock galaxies. We find that the dynamical masses within three-dimensional Re to the mock galaxy centres are overall averagely accurate within around 0.1 dex under the symmetric assumption, while Re means the projected circularized half-stellar mass radius in this work. We study the local virial mass estimation bias for mock galaxies of different η. The maximum bias difference of two η bins is around 0.16 dex, which with other local biases may help apply the observational virial mass estimators obtained from massive galaxies to other types of galaxies. We find that the Spearman’s ρ of η with the intrinsic mass estimation deviations is near zero if the local bias is eliminated properly. The results indicate that even for low-mass galaxies, the existence of high degree of kinematical small-scale fluctuations does not affect the measurement of the dynamical mass of galaxies.

Towards accurate field-level inference of massive cosmic structures

ABSTRACT We investigate the accuracy requirements for field-level inference of cluster and void masses using data from galaxy surveys. We introduce a two-step framework that takes advantage of the fact that cluster masses are determined by flows on larger scales than the clusters themselves. First, we determine the integration accuracy required to perform field-level inference of cosmic initial conditions on these large scales by fitting to late-time galaxy counts using the Bayesian Origin Reconstruction from Galaxies (BORG) algorithm. A 20-step COLA integrator is able to accurately describe the density field surrounding the most massive clusters in the local super-volume ($\lt 135\, {h^{-1}\mathrm{\, Mpc}}$), but does not by itself lead to converged virial mass estimates. Therefore, we carry out ‘posterior resimulations’, using full N-body dynamics while sampling from the inferred initial conditions, and thereby obtain estimates of masses for nearby massive clusters. We show that these are in broad agreement with existing estimates, and find that mass functions in the local super-volume are compatible with ΛCDM.

BASS. XXXV. The M BH–σ* Relation of 105 Month Swift-BAT Type 1 AGNs

We present two independent measurements of stellar velocity dispersions (σ ⋆) from the Ca ii H+K λ3969, 3934 and Mg i b λ 5183, 5172, 5167 region (3880–5550 Å) and the calcium triplet region (8350–8750 Å) for 173 hard X-ray-selected Type 1 active galactic nuclei (AGNs; z ≤ 0.08) from the 105 month Swift-BAT catalog. We construct one of the largest samples of local Type 1 AGNs that have both single-epoch virial black hole mass (M BH) estimates and σ ⋆ measurements obtained from high spectral resolution data, allowing us to test the usage of such methods for supermassive black hole studies. We find that the two independent σ ⋆ measurements are highly consistent with each other, with an average offset of only 0.002 ± 0.001 dex. Comparing M BH estimates based on broad emission lines and stellar velocity dispersion measurements, we find that the former is systematically lower by ≈0.12 dex. Consequently, Eddington ratios estimated through broad-line M BH determinations are similarly biased (but in the opposite way). We argue that the discrepancy is driven by extinction in the broad-line region. We also find an anticorrelation between the offset from the M BH–σ ⋆ relation and the Eddington ratio. Our sample of Type 1 AGNs shows a shallower M BH–σ ⋆ relation (with a power-law exponent of ≈3.5) compared with that of inactive galaxies (with a power-law exponent of ≈4.5), confirming earlier results obtained from smaller samples.

The Seoul National University AGN Monitoring Project. IV. Hα Reverberation Mapping of Six AGNs and the Hα Size–Luminosity Relation

The broad-line region (BLR) size–luminosity relation has paramount importance for estimating the mass of black holes in active galactic nuclei (AGNs). Traditionally, the size of the Hβ BLR is often estimated from the optical continuum luminosity at 5100 Å, while the size of the Hα BLR and its correlation with the luminosity is much less constrained. As a part of the Seoul National University AGN Monitoring Project, which provides 6 yr photometric and spectroscopic monitoring data, we present our measurements of the Hα lags of high-luminosity AGNs. Combined with the measurements for 42 AGNs from the literature, we derive the size–luminosity relations of the Hα BLR against the broad Hα and 5100 Å continuum luminosities. We find the slope of the relations to be 0.61 ± 0.04 and 0.59 ± 0.04, respectively, which are consistent with the Hβ size–luminosity relation. Moreover, we find a linear relation between the 5100 Å continuum luminosity and the broad Hα luminosity across 7 orders of magnitude. Using these results, we propose a new virial mass estimator based on the Hα broad emission line, finding that the previous mass estimates based on scaling relations in the literature are overestimated by up to 0.7 dex at masses lower than 107 M ⊙.

Uncertainty quantification of the virial black hole mass with conformal prediction

ABSTRACT Precise measurements of the black hole mass are essential to gain insight on the black hole and host galaxy co-evolution. A direct measure of the black hole mass is often restricted to nearest galaxies and instead, an indirect method using the single-epoch virial black hole mass estimation is used for objects at high redshifts. However, this method is subjected to biases and uncertainties as it is reliant on the scaling relation from a small sample of local active galactic nuclei. In this study, we propose the application of conformalized quantile regression (CQR) to quantify the uncertainties of the black hole predictions in a machine learning setting. We compare CQR with various prediction interval techniques and demonstrated that CQR can provide a more useful prediction interval indicator. In contrast to baseline approaches for prediction interval estimation, we show that the CQR method provides prediction intervals that adjust to the black hole mass and its related properties. That is it yields a tighter constraint on the prediction interval (hence more certain) for a larger black hole mass, and accordingly, bright and broad spectral line width source. Using a combination of neural network model and CQR framework, the recovered virial black hole mass predictions and uncertainties are comparable to those measured from the Sloan Digital Sky Survey. The code is publicly available.

The mass distribution of quasars in optical time-domain surveys

ABSTRACTThe determination of supermassive black hole (SMBH) masses is the key to understanding the host galaxy build-up and the SMBH mass assembly histories. The SMBH masses of non-local quasars are frequently estimated via the single-epoch virial black-hole mass estimators, which may suffer from significant biases. Here we demonstrate a new approach to infer the mass distribution of SMBHs in quasars by modelling quasar ultraviolet /optical variability. Our inferred black hole masses are systematically smaller than the virial ones by 0.3–0.6 dex; the ∼0.3 dex offsets are roughly consistent with the expected biases of the virial black-hole mass estimators. In the upcoming time-domain astronomy era, our methodology can be used to constrain the cosmic evolution of quasar mass distributions.

Characterising SMSS J2157–3602, the most luminous known quasar, with accretion disc models

ABSTRACT We develop an accretion disc (AD)-fitting method, utilizing thin and slim disc models and Bayesian inference with the Markov-Chain Monte Carlo approach, testing it on the most luminous known quasar, SMSS J215728.21-360215.1, at redshift z = 4.692. With a spectral energy distribution constructed from near-infrared spectra and broad-band photometry, the AD models find a black hole mass of $\log (M_{\rm {AD}}/{\rm M}_{\odot }) = 10.31^{+0.17}_{-0.14}$ with an anisotropy-corrected bolometric luminosity of $\log {(L_{\rm {bol}}/\rm {erg\, s^{-1}})} = 47.87 \pm 0.10$ and derive an Eddington ratio of $0.29^{+0.11}_{-0.10}$ as well as a radiative efficiency of $0.09^{+0.05}_{-0.03}$. Using the near-infrared spectra, we estimate the single-epoch virial black hole mass estimate to be log (MSE/M⊙) = 10.33 ± 0.08, with a monochromatic luminosity at 3000 Å of $\log {(L(\rm {3000{\AA}})/\rm {erg\, s^{-1}})} = 47.66 \pm 0.01$. As an independent approach, AD fitting has the potential to complement the single-epoch virial mass method in obtaining stronger constraints on properties of massive quasar black holes across a wide range of redshifts.

Dwarf AGNs from variability for the origins of seeds (DAVOS): optical variability of broad-line dwarf AGNs from the zwicky transient facility

ABSTRACTWe study the optical variability of a sample of candidate low-mass (dwarf and Seyfert) active galactic nuclei (AGNs) using Zwicky Transient Facility g-band light curves. Our sample is compiled from broad-line AGNs in dwarf galaxies reported in the literature with single-epoch virial black hole (BH) masses in the range MBH ∼ 104–108 M⊙. We measure the characteristic ‘damping’ time-scale of the optical variability τDRW, beyond which the power spectral density flattens, of a final sample of 79 candidate low-mass AGNs with high-quality light curves. Our results provide further confirmation of the MBH–τDRW relation from previous work within 1σ agreement, adding 78 new low-mass AGNs to the relation. The agreement suggests that the virial BH mass estimates for these AGNs are generally reasonable. We expect that the optical light curve of an accreting intermediate-mass black hole (IMBH) to vary with a rest-frame damping time-scale of ∼tens of hours, which could enable detection and direct mass estimation of accreting IMBHs in wide-field time-domain imaging surveys with sufficient cadence like with the Vera C. Rubin Observatory.

Statistical analysis of Al III and C III] emission lines as virial black hole mass estimators in quasars

Aims. We test the usefulness of the intermediate ionisation lines Al IIIλ1860 and C III]λ1909 as reliable virial mass estimators for quasars. Methods. We identified a sample of 309 quasars from the Sloan Digital Sky Survey Data Release 16 (SDSS DR16) in the redshift range 1.2 ≤ z ≤ 1.4 that have [O II]λ3728 recorded on the same spectrum as Al IIIλ1860, Si III]λ1892, and C III]λ1909. We set the systemic quasar redshift using careful measurements of [O II]λ3728. We then classified the sources as Population A (Pop. A), extreme Population A (Pop. xA), and Population B (Pop. B), and analysed the 1900 Å blend using multi-component models to look for systematic line shifts of Al IIIλ1860 and C III]λ1909 along the quasar main sequence. Results. We do not find significant shifts of the Al IIIλ1860 line peak in Pop. B or in the vast majority of Pop. A. For Pop. xA, a small median blueshift of −250 km s−1 was observed, motivating a decomposition of the Al III line profile into a virialised component centred at rest frame and a blueshifted component for an outflow emission. For Pop. B objects, we proved the empirical necessity to fit a redshifted very broad component, clearly seen in C III], and analysed the physical implications on a Pop. B composite spectrum using CLOUDY simulations. We find consistent black hole mass estimations using Al III and C III] as virial estimators for the bulk of Pop. A. Conclusions. Al III (and even C III]) is a reliable virial black hole mass estimator for Pop. A and Pop. B objects. The Pop. xA sources deserve special attention due to the significant blueshifted excess observed in the line profile of Al III, although it is not as large as the excess observed in C IVλ1549.

Deep absorption in SDSS J110511.15+530806.5

Aims. We study the origin of the anomalous deep absorption in a spectrum of the SDSS J110511.15+530806.5 distant quasar (z = 1.929) obtained by the Sloan Digital Sky Survey in Data Release 14 of the optical catalog. We aim to estimate the velocity of absorbing material, and we show that this material considerably affects our measurements of the black hole (BH) mass in massive quasars with the use of common virial mass estimators. Methods. The spectral shape of the quasar was modeled assuming that the accretion disk emission is influenced by a hot corona, warm skin, and absorbing material located close to the nucleus. The whole analysis was undertaken with XSPEC models and tools. The overall spectral shape was represented with the AGNSED model, while the deep absorption is well described by two Gaussians. Results. The observed spectrum and the fitting procedure allowed us to estimate the BH mass in the quasar as 3.52 ± 0.01 × 109 M⊙, the nonzero BH spin is a* = 0.32 ± 0.04, and the accretion rate is ṁ = 0.274 ± 0.001. The velocities of the detected absorbers lie in the range of 6330–108 135 km s−1. When we consider that absorption is caused by the C IV ion, one absorber is folding toward the nucleus with a velocity of 73 887 km s−1. We derived a BI index of about 20 300 km s−1 and a mass outflow rate up to 38.5% of the source accretion rate. Conclusions. The high absorption observed in SDSS J110511.15+530806.5 is evidence of fast winds that place the source in the group of objects on the border with UFO (ultra-fast outflows), strong broad absorption line, and fast failed radiatively accelerated dusty outflow (FRADO). This absorption affects the BH mass measurement by two orders of magnitude as compared to virial mass estimation.

AGNet: weighing black holes with deep learning

ABSTRACT Supermassive black holes (SMBHs) are commonly found at the centres of most massive galaxies. Measuring SMBH mass is crucial for understanding the origin and evolution of SMBHs. Traditional approaches, on the other hand, necessitate the collection of spectroscopic data, which is costly. We present an algorithm that weighs SMBHs using quasar light time series information, including colours, multiband magnitudes, and the variability of the light curves, circumventing the need for expensive spectra. We train, validate, and test neural networks that directly learn from the Sloan Digital Sky Survey (SDSS) Stripe 82 light curves for a sample of 38 939 spectroscopically confirmed quasars to map out the non-linear encoding between SMBH mass and multiband optical light curves. We find a 1σ scatter of 0.37 dex between the predicted SMBH mass and the fiducial virial mass estimate based on SDSS single-epoch spectra, which is comparable to the systematic uncertainty in the virial mass estimate. Our results have direct implications for more efficient applications with future observations from the Vera C. Rubin Observatory. Our code, AGNet, is publicly available at https://github.com/snehjp2/AGNet.

The SAMI–Fornax Dwarfs Survey – II. The Stellar Mass Fundamental Plane and the dark matter fraction of dwarf galaxies

ABSTRACT We explore the kinematic scaling relations of 38 dwarf galaxies in the Fornax Cluster using observations from the SAMI integral field spectrograph. We focus on the Fundamental Plane (FP), defined by the physical properties of the objects (scale length, surface brightness, and velocity dispersion) and the Stellar Mass (Fundamental) Plane, where surface brightness is replaced by stellar mass, and investigate their dynamical-to-stellar-mass ratio. We confirm earlier results that the Fornax dEs are significantly offset above the FP defined by massive, hot stellar systems. For the Stellar Mass (Fundamental) Plane, which shows much lower scatter, we find that young and old dwarf galaxies lie at about the same distance from the plane, all with comparable scatter. We introduce the perpendicular deviation of dwarf galaxies from the Stellar Mass Plane defined by giant early-types as a robust estimate of their DM fraction, and find that the faintest dwarfs are systematically offset above the plane, implying that they have a higher dark matter fraction. This result is confirmed when estimating the dynamical mass of our dEs using a virial mass estimator, tracing the onset of dark matter domination in low mass stellar systems. We find that the position of our galaxies on the Stellar Mass FP agrees with the galaxies in the Local Group. This seems to imply that the processes determining the position of dwarf galaxies on the FP depend on the environment in the same way, whether the galaxy is situated in the Local Group or in the Fornax Cluster.

The Mass Scale of High-redshift Galaxies: Virial Mass Estimates Calibrated with Stellar Dynamical Models from LEGA-C

Dynamical models for 673 galaxies at z = 0.6–1.0 with spatially resolved (long-slit) stellar kinematic data from LEGA-C are used to calibrate virial mass estimates defined as , with K a scaling factor, the spatially integrated stellar velocity second moment from the LEGA-C survey, and R the effective radius measured from a Sérsic profile fit to Hubble Space Telescope imaging. The sample is representative for M ⋆ > 3 × 1010 M ⊙ and includes all types of galaxies, irrespective of morphology and color. We demonstrate that using R = R sma (the semimajor axis length of the ellipse that encloses 50% of the light) in combination with an inclination correction on produces an unbiased M vir. We confirm the importance of projection effects on by showing the existence of a similar residual trend between virial mass estimates and inclination for the nearby early-type galaxies in the ATLAS3D survey. Also, as previously shown, when using a Sérsic profile-based R estimate, a Sérsic index-dependent correction to account for nonhomology in the radial profiles is required. With respect to analogous dynamical models for low-redshift galaxies from the ATLAS3D survey we find a systematic offset of 0.1 dex in the calibrated virial constant for LEGA-C, which may be due to physical differences between the galaxy samples or an unknown systematic error. Either way, with our work we establish a common mass scale for galaxies across 8 Gyr of cosmic time with a systematic uncertainty of at most 0.1 dex.

Local Group timing argument and virial theorem mass estimators from cosmological simulations

ABSTRACT We identify Local Group (LG) analogues in the IllustrisTNG cosmological simulation, and use these to study two-mass estimators for the LG: One based on the timing argument (TA) and one based on the virial theorem (VT). Including updated measurements of the Milky Way-M31 tangential velocity and the cosmological constant, we show that the TA mass estimator slightly overestimates the true median LG-mass, though the ratio of the TA to the true mass is consistent at the approximate 90 per cent c.l.. These are in broad agreement with previous results using dark matter-only simulations. We show that the VT estimator better estimates the true LG-mass, though there is a larger scatter in the virial mass to true mass ratio relative to the corresponding ratio for the TA. We attribute the broader scatter in the VT estimator to several factors, including the predominantly radial orbits for LG satellite galaxies, which differs from the VT assumption of isotropic orbits. With the systematic uncertainties we derive, the updated measurements of the LG mass at 90 per cent c.l. are $4.75_{-2.41}^{+2.22} \times 10^{12}$ M⊙ from the TA and $2.0_{-1.5}^{+2.1} \times 10^{12}$ M⊙ from the VT. We consider the LMC’s effect on the TA and VT LG mass estimates, and do not find exact LMC–MW–M31 analogues in the Illustris simulations. However, in LG simulations with satellite companions as massive as the LMC, we find that the effect on the TA and VT estimators is small, though we need further studies on a larger sample of LMC–MW–M31 systems to confirm these results.

The Lick AGN Monitoring Project 2016: Velocity-resolved Hβ Lags in Luminous Seyfert Galaxies

Abstract We carried out spectroscopic monitoring of 21 low-redshift Seyfert 1 galaxies using the Kast double spectrograph on the 3 m Shane telescope at Lick Observatory from 2016 April to 2017 May. Targeting active galactic nuclei (AGNs) with luminosities of λ L λ (5100 Å) ≈ 1044 erg s−1 and predicted Hβ lags of ∼20–30 days or black hole masses of 107–108.5 M ⊙, our campaign probes luminosity-dependent trends in broad-line region (BLR) structure and dynamics as well as to improve calibrations for single-epoch estimates of quasar black hole masses. Here we present the first results from the campaign, including Hβ emission-line light curves, integrated Hβ lag times (8–30 days) measured against V-band continuum light curves, velocity-resolved reverberation lags, line widths of the broad Hβ components, and virial black hole mass estimates (107.1–108.1 M ⊙). Our results add significantly to the number of existing velocity-resolved lag measurements and reveal a diversity of BLR gas kinematics at moderately high AGN luminosities. AGN continuum luminosity appears not to be correlated with the type of kinematics that its BLR gas may exhibit. Follow-up direct modeling of this data set will elucidate the detailed kinematics and provide robust dynamical black hole masses for several objects in this sample.

Synchronized Coevolution between Supermassive Black Holes and Galaxies over the Last Seven Billion Years as Revealed by Hyper Suprime-Cam

Abstract We measure the evolution of the  BH –  ⋆ relation using 584 uniformly selected Sloan Digital Sky Survey quasars at 0.2 &lt; z &lt; 0.8. The black hole masses (  BH ) are derived from the single-epoch virial mass estimator using the Hβ emission line and span the range 7.0 &lt; log  BH / M ⊙ &lt; 9.5 . The host-galaxy stellar masses (  ⋆ ), which cover the interval 10.0 &lt; log  ⋆ / M ⊙ &lt; 11.5 , are determined by performing two-dimensional quasar-host decomposition of the Hyper Suprime-Cam images and spectral energy distribution fitting. To quantify sample selection biases and measurement uncertainties on the mass terms, a mock quasar sample is constructed to jointly constrain the redshift evolution of the  BH –  ⋆ relation and its intrinsic scatter (σ μ ) through forward modeling. We find that the level of evolution is degenerate with σ μ , such that both a positive mild evolution (i.e.,  BH /  ⋆ increases with redshift) with a small σ μ and a negative mild evolution with a larger σ μ are consistent with our data. The posterior distribution of σ μ enables us to put a strong constraint on the intrinsic scatter of the  BH –  ⋆ relation, which has a best inference of 0.25 − 0.04 + 0.03 dex, consistent with the local value. The redshift evolution of the  BH –  ⋆ relation relative to the local relation is constrained to be 1 + z 0.12 − 0.27 + 0.28 , in agreement with no significant evolution since z ∼ 0.8. The tight and unevolving  BH –  ⋆ relation is suggestive of a coupling through active galactic nuclei feedback or/and a common gas supply at work, thus restricting the mass ratio of galaxies and their black holes to a limited range. Given the considerable stellar disk component, the  BH –  bulge relation may evolve as previously seen at higher redshifts.

High-redshift Extreme Variability Quasars from Sloan Digital Sky Survey Multiepoch Spectroscopy

Abstract We perform a systematic search for high-redshift ( 1.5) extreme variability quasars (EVQs) using repeat spectra from the Sixteenth Data Release of the Sloan Digital Sky Survey, which provides a baseline spanning up to ∼18 yr in the observed frame. We compile a sample of 348 EVQs with a maximum continuum variability at rest frame 1450 Å of more than 100% (i.e., δV ≡ (Max − Min)/Mean &gt; 1). The EVQs show a range of emission-line variability, including 23 where at least one line in our redshift range disappears below detectability, which can then be seen as analogous to low-redshift changing-look quasars (CLQs). Importantly, spurious CLQs caused by problematic SDSS spectral flux calibration, e.g., fiber-drop issue, have been rejected. The similar properties (e.g., continuum/line, difference-composite spectra and Eddington ratio) of normal EVQs and CLQs imply that they are basically the same physical population with analogous intrinsic variability mechanisms, as a tail of a continuous distribution of normal quasar properties. In addition, we find no reliable evidence (≲1σ) to support that CLQs are a subset of EVQs with less efficient accretion. Finally, we also confirm the antibreathing of C iv (i.e., the line width increases as luminosity increases) in EVQs and find that in addition to the ∼0.4 dex systematic uncertainty in single-epoch C iv virial black hole mass estimates, an extra scatter of ∼0.3 dex will be introduced by extreme variability.