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Evident black hole-bulge coevolution in the distant universe.

Yang(杨光), G. and Brandt, W. N. and Alexander, D. M. and Chen(陳建廷), C-T. J. and Ni(倪清泠), Q. and Vito, F. and Zhu(朱飞凡), F-F. (2019) 'Evident black hole-bulge coevolution in the distant universe.', Monthly notices of the Royal Astronomical Society., 485 (3). pp. 3721-3737.


Observations in the local universe show a tight correlation between the masses of supermassive black holes (SMBHs; MBH) and host-galaxy bulges (Mbulge), 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) for bulge-dominated galaxies at z = 0.5–3. While previous observations found BHAR is strongly related to host-galaxy stellar mass (M) for the overall galaxy population, our analyses show that, for the bulge-dominated population, BHAR is mainly related to SFR rather than M. This BHAR–SFR relation is highly significant, e.g. 9.0σ (Pearson statistic) at z = 0.5–1.5. Such a BHAR–SFR connection does not exist among our comparison sample of galaxies that are not bulge dominated, for which M 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 MBH−Mbulge correlation. Our best-fitting BHAR–SFR relation for the bulge-dominated sample is logBHAR = log SFR − (2.48 ± 0.05) (solar units). The best-fitting BHAR/SFR ratio (10−2.48) for bulge-dominated galaxies is similar to the observed MBH/Mbulge 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 MBH−Mbulge correlation. This lockstep growth also predicts that the MBH−Mbulge relation should not have strong redshift dependence.

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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2019 The Author[s]. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:26 February 2019
Date deposited:30 July 2019
Date of first online publication:02 March 2019
Date first made open access:No date available

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