VLT/SINFONI study of black hole growth in high-redshift radio-loud quasars from the CARLA survey

Abstract

ABSTRACT We present Very Large Telescope/Spectrograph for INtegral Field Observations in the Near Infrared (VLT/SINFONI) observations of 35 quasars at 2.1 < z < 3.2, the majority of which were selected from the Clusters Around Radio-Loud AGN (CARLA) survey. CARLA quasars have large C iv-based black hole masses (MBH > 109 M⊙) and powerful radio emission ($P_{500\, \rm MHz}$ > 27.5 W Hz−1). We estimate H α-based MBH, finding a scatter of 0.35 dex compared to C iv. We evaluate several recipes for correcting C iv-based masses, which reduce the scatter to 0.24 dex. The radio power of the radio-loud quasars is at most weakly correlated with the interconnected quantities H αwidth, L5100, and MBH, suggesting that it is governed by different physical processes. However, we do find a strong inverse correlation between C iv blueshift and radio power linked to higher Eddington ratios and L5100. Under standard assumptions, the black hole (BH) growth time is longer than the cosmic age for many CARLA quasars, suggesting that they must have experienced more efficient growth in the past. If these BHs were growing from seeds since the epoch of reionization, it is possible that they grew at the Eddington limit like the quasars at z ∼ 6–7, and then continued to grow at the reduced rates observed until z ∼ 2–3. Finally, we study the relation between MBH and environment, finding a weak positive correlation between MBH and galaxydensity measured by CARLA.