skip to main content

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Systematically smaller single-epoch quasar black hole masses using a radius–luminosity relationship corrected for spectral bias
Title: Systematically smaller single-epoch quasar black hole masses using a radius–luminosity relationship corrected for spectral bias
ABSTRACT

Determining black hole masses and accretion rates with better accuracy and precision is crucial for understanding quasars as a population. These are fundamental physical properties that underpin models of active galactic nuclei. A primary technique to measure the black hole mass employs the reverberation mapping of low-redshift quasars, which is then extended via the radius–luminosity relationship for the broad-line region to estimate masses based on single-epoch spectra. An updated radius–luminosity relationship incorporates the flux ratio of optical Fe ii to H β ($\equiv \mathcal {R}_{\rm Fe}$) to correct for a bias in which more highly accreting systems have smaller line-emitting regions than previously realized. In this work, we demonstrate and quantify the effect of using this Fe-corrected radius-luminosity relationship on mass estimation by employing archival data sets possessing rest-frame optical spectra over a wide range of redshifts. We find that failure to use an Fe-corrected radius predictor results in overestimated single-epoch black hole masses for the most highly accreting quasars. Their accretion rate measures (LBol/LEdd and $\dot{\mathscr{M}}$ ) are similarly underestimated. The strongest Fe-emitting quasars belong to two classes: high-z quasars with rest-frame optical spectra, which, given their extremely high luminosities, require high accretion rates, and their low-z analogues, which, given their low black holes masses, must have high accretion rates to meet survey flux limits. These classes have mass corrections downward of about a factor of two, on average. These results strengthen the association of the dominant Eigenvector 1 parameter $\mathcal {R}_{\rm Fe}$ with the accretion process.

  more » « less
Award ID(s):
1815645
PAR ID:
10425585
Author(s) / Creator(s):
; ; ; ; ; ; ; ;
Publisher / Repository:
Oxford University Press
Date Published:
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
515
Issue:
1
ISSN:
0035-8711
Page Range / eLocation ID:
p. 491-506
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; ( , Proceedings of the International Astronomical Union)
    null (Ed.)
    Abstract Quasar black hole masses are most commonly estimated using broad emission lines in single epoch spectra based on scaling relationships determined from reverberation mapping of small samples of low-redshift objects. Several effects have been identified requiring modifications to these scaling relationships, resulting in significant reductions of the black hole mass determinations at high redshift. Correcting these systematic biases is critical to understanding the relationships among black hole and host galaxy properties. We are completing a program using the Gemini North telescope, called the Gemini North Infrared Spectrograph (GNIRS) Distant Quasar Survey (DQS), that has produced rest-frame optical spectra of about 200 high-redshift quasars (z = 1.5–3.5). The GNIRS-DQS will produce new and improved ultraviolet-based black hole mass and accretion rate prescriptions, as well as new redshift prescriptions for velocity zero points of high-z quasars, necessary to measure feedback. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ; et al ( , Monthly Notices of the Royal Astronomical Society)
    ABSTRACT

    The elemental abundances in the broad-line regions of high-redshift quasars trace the chemical evolution in the nuclear regions of massive galaxies in the early Universe. In this work, we study metallicity-sensitive broad emission-line flux ratios in rest-frame UV spectra of 25 high-redshift (5.8 < z < 7.5) quasars observed with the VLT/X-shooter and Gemini/GNIRS instruments, ranging over $\log \left({{M}_{\rm {BH}}/\rm {M}_{\odot }}\right) = 8.4-9.8$ in black hole mass and $\log \left(\rm {L}_{\rm {bol}}/\rm {erg \, s}^{-1}\right) = 46.7-47.7$ in bolometric luminosity. We fit individual spectra and composites generated by binning across quasar properties: bolometric luminosity, black hole mass, and blueshift of the C iv line, finding no redshift evolution in the emission-line ratios by comparing our high-redshift quasars to lower redshift (2.0 < z < 5.0) results presented in the literature. Using cloudy-based locally optimally emitting cloud photoionization model relations between metallicity and emission-line flux ratios, we find the observable properties of the broad emission lines to be consistent with emission from gas clouds with metallicity that are at least 2–4 times solar. Our high-redshift measurements also confirm that the blueshift of the C iv emission line is correlated with its equivalent width, which influences line ratios normalized against C iv. When accounting for the C iv blueshift, we find that the rest-frame UV emission-line flux ratios do not correlate appreciably with the black hole mass or bolometric luminosity.

     
    more » « less
  3. ; ; ; ; ( , Monthly Notices of the Royal Astronomical Society)
    ABSTRACT

    We investigate the black hole mass function at z ∼ 5 using XQz5, our recent sample of the most luminous quasars between the redshifts 4.5 < z < 5.3. We include 72 quasars with black hole masses estimated from velocity-broadened emission-line measurements and single-epoch virial prescriptions in the footprint of a highly complete parent survey. The sample mean Eddington ratio and standard deviation is log λ ≈ −0.20 ± 0.24. The completeness-corrected mass function is modelled as a double power law, and we constrain its evolution across redshift assuming accretion-dominated mass growth. We estimate the evolution of the mass function from z = 5–4, presenting joint constraints on accretion properties through a measured dimensionless e-folding parameter, kef ≡ 〈λ〉U(1 − ϵ)/ϵ = 1.79 ± 0.06, where 〈λ〉 is the mean Eddington ratio, U is the duty cycle, and ϵ is the radiative efficiency. If these supermassive black holes were to form from seeds smaller than $10^8\, {\rm M}_{\odot }$, the growth rate must have been considerably faster at z ≫ 5 than observed from z = 5–4. A growth rate exceeding 3 × the observed rate would reduce the initial heavy seed mass to $10^{5-6}\, {\rm M}_{\odot }$, aligning with supermassive star and/or direct collapse seed masses. Stellar mass ($10^2\, {\rm M}_{\odot }$) black hole seeds would require ≳4.5 × the observed growth rate at z ≫ 5 to reproduce the measured active black hole mass function. A possible pathway to produce the most extreme quasars is radiatively inefficient accretion flow, suggesting black holes with low angular momentum or photon trapping in supercritically accreting thick discs.

     
    more » « less
  4. ; ; ; ; ; ; ; ; ; ; et al ( , The Astrophysical Journal)
    Abstract

    We present the rest-frame ultraviolet−optical spectral properties of 65 broad absorption line (BAL) quasars from the Gemini Near Infrared Spectrograph−Distant Quasar Survey (GNIRS-DQS). These properties are compared with those of 195 non-BAL quasars from GNIRS-DQS in order to identify the drivers for the appearance of BALs in quasar spectra. In particular, we compare equivalent widths and velocity widths, as well as velocity offsets from systemic redshifts, of principal emission lines. In spite of the differences between their rest-frame ultraviolet spectra, we find that luminous BAL quasars are generally indistinguishable from their non-BAL counterparts in the rest-frame optical band at redshifts 1.55 ≲z≲ 3.50. We do not find any correlation between BAL trough properties and the Hβ-based supermassive black hole masses and normalized accretion rates in our sample. Considering the Sloan Digital Sky Survey quasar sample, which includes the GNIRS-DQS sample, we find that a monochromatic luminosity at rest-frame 2500 Å of ≳1045erg s−1is a necessary condition for launching BAL outflows in quasars. We compare our findings with other BAL quasar samples and discuss the roles that accretion rate and orientation play in the appearance of BAL troughs in quasar spectra.

     
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al ( , The Astrophysical Journal)
    Abstract

    Weak emission-line quasars (WLQs) are a subset of type 1 quasars that exhibit extremely weak Lyα+ Nvλ1240 and/or Civλ1549 emission lines. We investigate the relationship between emission-line properties and accretion rate for a sample of 230 “ordinary” type 1 quasars and 18 WLQs atz< 0.5 and 1.5 <z< 3.5 that have rest-frame ultraviolet and optical spectral measurements. We apply a correction to the Hβ-based black hole mass (MBH) estimates of these quasars using the strength of the optical Feiiemission. We confirm previous findings that WLQs’MBHvalues are overestimated by up to an order of magnitude using the traditional broad-emission-line region size–luminosity relation. With thisMBHcorrection, we find a significant correlation between Hβ-based Eddington luminosity ratios and a combination of the rest-frame Civequivalent width and Civblueshift with respect to the systemic redshift. This correlation holds for both ordinary quasars and WLQs, which suggests that the two-dimensional Civparameter space can serve as an indicator of accretion rate in all type 1 quasars across a wide range of spectral properties.

     
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email