No Significant Evolution of Relations between Black Hole Mass and Galaxy Total Stellar Mass Up to z ∼ 2.5

We investigate the cosmic evolution of the ratio between black hole (BH) mass (M _BH) and host galaxy total stellar mass (M _stellar) out to z ∼ 2.5 for a sample of 100 X-ray-selected moderate-luminosity, broad-line active galactic nuclei (AGNs) in the Chandra-COSMOS Legacy Survey. By taking advantage of the deep multiwavelength photometry and spectroscopy in the COSMOS field, we measure in a uniform way the galaxy total stellar mass using an spectral energy distribution decomposition technique and the BH mass based on broad emission line measurements and single-epoch virial estimates. Our sample of AGN host galaxies has total stellar masses of 10¹⁰⁻¹² M _⊙, and BH masses of 10^7.0–9.5 M _⊙. Combining our sample with the relatively bright AGN samples from the literature, we find no significant evolution of the M _BH–M _stellar relation with the BH-to-host total stellar mass ratio of M _BH/M _stellar ∼ 0.3% at all redshifts probed. We conclude that the average BH-to-host stellar mass ratio appears to be consistent with the local value within the uncertainties, suggesting a lack of evolution of the M _BH–M _stellar relation up to z ∼ 2.5.