We investigate the cosmic evolution of the black hole ( BH ) mass – bulge luminosity relation using a sample of 52 active galaxies at z \sim 0.36 and z \sim 0.57 in the BH mass range of 10 ^ { 7.4 - 9.1 } M _ { \odot } .
By consistently applying multi-component spectral and structural decomposition to high-quality Keck spectra and high-resolution HST images , BH masses ( M _ { BH } ) are estimated using the H \beta broad emission line combined with the 5100 Å nuclear luminosity , and bulge luminosities ( L _ { bul } ) are derived from surface photometry .
Comparing the resulting M _ { BH } - L _ { bul } relation to local active galaxies and taking into account selection effects , we find evolution of the form M _ { BH } / L _ { bul } \propto ( 1 + z ) ^ { \gamma } with \gamma = 1.8 \pm 0.7 , consistent with BH growth preceding that of the host galaxies .
Including an additional sample of 27 active galaxies with 0.5 < z < 1.9 taken from the literature and measured in a consistent way , we obtain \gamma = 0.9 \pm 0.7 for the M _ { BH } - L _ { bul } relation and \gamma = 0.4 \pm 0.5 for the M _ { BH } –total host galaxy luminosity ( L _ { host } ) relation .
The results strengthen the findings from our previous studies and provide additional evidence for host-galaxy bulge growth being dominated by disk-to-bulge transformation via minor mergers and/or disk instabilities .