Virial Black Hole Mass Estimates of Quasars in the XQ-100 Legacy Survey

TL;DR

This study uses high-quality spectra from the XQ-100 survey to estimate black hole masses in luminous quasars at redshift 3.5-4.5, employing multiple emission lines for accurate virial mass calculations.

Contribution

It provides the first comprehensive comparison of virial black hole mass estimates using CIV, MgII, and Hβ lines in high-redshift quasars, demonstrating their tight correlation.

Findings

Black hole masses range from 10^8.6 to 10^10.3 solar masses.

Bolometric luminosities span from 10^46.7 to 10^48.0 erg/s.

Strong correlation between mass estimates from different emission lines.

Abstract

The black hole (BH) mass and luminosity are key factors in determining how a quasar interacts with its environment. In this study, we utilise data from the European Southern Observatory Large Programme XQ-100, a high-quality sample of 100 X-shooter spectra of the most luminous quasars in the redshift range $3.5 < z < 4.5$, and measure the properties of three prominent optical and ultraviolet broad emission-lines present in the wide wavelength coverage of X-shooter: CIV, MgII, and H$\beta$. The line properties of all three broad lines are used for virial estimates of the BH mass and their resulting mass estimates for this sample are tightly correlated. The BH mass range is $\log{(\rm{M_{BH}}/\rm{M_\odot})} = 8.6-10.3$ with bolometric luminosities estimated from the 3000A continuum in the range $\log{(\rm{L_{bol}}/\rm{erg\,s^{-1}})} = 46.7-48.0$. Robustly determined properties of these quasars enable a variety of follow-up research in quasar astrophysics, from chemical abundance and evolution in the broad-line region to radiatively driven quasar outflows.