Black Hole Masses and Host Galaxy Evolution of Radio-Loud Active Galactic Nuclei

We report stellar velocity dispersion measurements for a sample of 28 active galactic nucleus (AGN) host galaxies, including our previous work. Using the mass-dispersion (M_•-σ) and the fundamental plane relations, we estimate the black hole mass for a sample of 66 BL Lac objects and investigate the role of black hole mass in the energetics of BL Lac objects. The black hole mass range for different BL Lac spectral types is similar, 10⁷ < M_• < 4 × 10⁹. Neither X-ray nor radio luminosity correlates with black hole mass. Low-frequency-peaked BL Lac objects have higher Eddington ratios on average, because of either more beaming or higher intrinsic power. For the black hole mass range 3 × 10⁷ < M_• < 10⁹, the radio luminosity of BL Lac objects and flat-spectrum radio quasars spans over 4 orders of magnitude, with BL Lac objects being low-power AGNs. We also investigate the evolution of host galaxies for 39 AGNs out to z ≈ 0.5 with measured stellar velocity dispersions. Comparing the mass-to-light ratio evolution in the observed frame with population synthesis models, we find that single-burst star formation models with z_form = 1.4 are consistent with the observations. From our z_form = 1.4 model, we estimated the intrinsic mass-to-light ratio evolution in the Cousins R band, Δ log(M/L)/Δz = -0.502 ± 0.08, consistent with that of normal early-type galaxies.