Cosmic Evolution of Black Holes and Spheroids. III. The M BH ‐σ * Relation in the Last Six Billion Years

Abstract

We measure the evolution of the correlation between black hole mass and host spheroid velocity dispersion (MBH-σ*) over the last 6 billion years, by studying three carefully selected samples of active galaxies at z=0.57, z=0.36 and z<0.1. For all three samples, virial black hole masses are consistently estimated using the line dispersion of Hβ and the continuum luminosity at 5100 Å or Hα line luminosity, based on our cross calibration of the broad-line region size-luminosity relation. For the z=0.57 sample, new stellar velocity dispersions are measured from high signal-to-noise ratio spectra obtained at the Keck Telescope, while for the two lower redshift samples they are compiled from previous works. Extending our previous result at z=0.36, we find an offset from the local relation, suggesting that for fixed MBH, distant spheroids have on average smaller velocity dispersions than local ones. The measured offset at z=0.57 is Δlogσ*=0.12+/-0.05+/-0.06 (or ΔlogMBH=0.50+/-0.22+/-0.25), i.e., ΔlogMBH=(3.1+/-1.5)log(1+z)+0.05+/-0.21. This is inconsistent with a tight and nonevolving universal MBH-σ* relation at the 95% CL.