# CIV Black Hole Mass Measurements with the Australian Dark Energy Survey (OzDES)

## TL;DR

This paper reports two new high-redshift supermassive black hole mass measurements using reverberation mapping with data from the OzDES survey, advancing understanding of black hole growth and the CIV radius-luminosity relation.

## Contribution

It provides the first reverberation mapping measurements of supermassive black holes at redshifts above 2, improving the CIV radius-luminosity relationship for high-luminosity quasars.

## Key findings

- Measured black hole masses of 4.4 and 3.3 billion solar masses.
- Determined reverberation lags of approximately 358 and 343 days.
- Extended the CIV radius-luminosity relationship to higher redshifts.

## Abstract

Black hole mass measurements outside the local universe are critically important to derive the growth of supermassive black holes over cosmic time, and to study the interplay between black hole growth and galaxy evolution. In this paper we present two measurements of supermassive black hole masses from reverberation mapping (RM) of the broad CIV emission line. These measurements are based on multi-year photometry and spectroscopy from the Dark Energy Survey Supernova Program (DES-SN) and the Australian Dark Energy Survey (OzDES), which together constitute the OzDES RM Program. The observed reverberation lag between the DES continuum photometry and the OzDES emission-line fluxes is measured to be $358^{+126}_{-123}$ and $343^{+58}_{-84}$ days for two quasars at redshifts of $1.905$ and $2.593$ respectively. The corresponding masses of the two supermassive black holes are $4.4 \times 10^{9}$ and $3.3 \times 10^{9}$ M$_\odot$, which are among the highest-redshift and highest-mass black holes measured to date with RM studies. We use these new measurements to better determine the CIV radius$-$luminosity relationship for high-luminosity quasars, which is fundamental to many quasar black hole mass estimates and demographic studies.