Browsing by Author "Chen, C. -T. J."

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    Evident black hole-bulge coevolution in the distant universe
    (2019) Yang, G.; Brandt, W. N.; Alexander, D. M.; Chen, C. -T. J.; Ni, Q.; Vito, F.; Zhu, F. -F.
    Observations in the local universe show a tight correlation between the masses of supermassive black holes (SMBHs; M-BH) and host-galaxy bulges (M-bulge), suggesting a strong connection between SMBH and bulge growth. However, direct evidence for such a connection in the distant universe remains elusive. We have studied sample-averaged SMBH accretion rate ((BHAR) over bar) for bulge-dominated galaxies at z = 0.5-3. While previous observations found (BHAR) over bar is strongly related to host-galaxy stellar mass (M-star) for the overall galaxy population, our analyses show that, for the bulge-dominated population, (BHAR) over bar is mainly related to SFR rather than M-star. This (BHAR) over bar -SFR relation is highly significant, e.g. 9.0 sigma (Pearson statistic) at z = 0.5-1.5. Such a (BHAR) over bar -SFR connection does not exist among our comparison sample of galaxies that are not bulge dominated, for which M-star appears to be the main determinant of SMBH accretion. This difference between the bulge-dominated and comparison samples indicates that SMBHs only coevolve with bulges rather than the entire galaxies, explaining the tightness of the local M-BH - M-bulge correlation. Our best-fitting (BHAR) over bar -SFR relation for the bulge-dominated sample is log (BHAR) over bar = log SFR - (2.48 +/- 0.05) (solar units). The best-fitting (BHAR) over bar /SFR ratio (10(-2.48)) for bulge-dominated galaxies is similar to the observed M-BH/M-bulge values in the local universe. Our results reveal that SMBH and bulge growth are in lockstep, and thus non-causal scenarios of merger averaging are unlikely the origin of the M-BH-M-bulge correlation. This lockstep growth also predicts that the M-BH-M-bulge relation should not have strong redshift dependence.