Stellar Dynamics and Star Formation Histories of z ∼ 1 Radio-loud Galaxies
Bell, Eric F.; Maseda, Michael V.; van Dokkum, Pieter G.; Franx, Marijn; Muzzin, Adam; Labbé, Ivo; van der Wel, Arjen; van Houdt, Josha; Bezanson, Rachel; Pacifici, Camilla; Gallazzi, Anna; Sobral, David; Brammer, Gabriel; Wu, Po-Feng; Noeske, Kai; Barišić, Ivana; Straatman, Caroline; Smolčić, Vernesa; Calhau, João; Muñoz-Mateos, Juan C.; Chauké, Priscilla
Germany, United States, Chile, Netherlands, Croatia, United Kingdom, Italy, Canada
Abstract
We investigate the stellar kinematics and stellar populations of 58 radio-loud galaxies of intermediate luminosities (L 3 GHz > 1023 W Hz-1) at 0.6 < z < 1. This sample is constructed by cross-matching galaxies from the deep VLT/VIMOS LEGA-C spectroscopic survey with the VLA 3 GHz data set. The LEGA-C continuum spectra reveal for the first time stellar velocity dispersions and age indicators of z ∼ 1 radio galaxies. We find that z ∼ 1 radio-loud active galactic nucleus (AGN) occur exclusively in predominantly old galaxies with high velocity dispersions: σ * > 175 km s-1, corresponding to black hole masses in excess of 108 M ⊙. Furthermore, we confirm that at a fixed stellar mass the fraction of radio-loud AGN at z ∼ 1 is five to 10 times higher than in the local universe, suggesting that quiescent, massive galaxies at z ∼ 1 switch on as radio AGN on average once every Gyr. Our results strengthen the existing evidence for a link between high black hole masses, radio loudness, and quiescence at z ∼ 1.