Supermassive black holes with higher Eddington ratios preferentially form in gas-rich galaxies

PASJ: Publications of the Astronomical Society of Japan

Izumi, Takuma¹ 

[1] National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan

关键词: galaxies: active;    galaxies: evolution;    ISM: molecules;   

DOI  :  10.1093/pasj/psy045

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

The Eddington ratio (λEdd) of supermassive black holes (SMBHs) is a fundamental parameter that governs their cosmic growth. Although gas mass accretion onto SMBHs is sustained when they are surrounded by large amounts of gas, little is known about the molecular content of galaxies, particularly those hosting super-Eddington SMBHs (λEdd > 1: the key phase of SMBH growth). Here, we have compiled reported optical and 12CO(1–0) data of local quasars to characterize their hosts. We found that higher-λEdd SMBHs tend to reside in gas-rich (i.e., high gas mass to stellar mass fraction = fgas) galaxies. We used two methods to make this conclusion: one uses black hole mass as a surrogate for stellar mass by assuming a local co-evolutionary relationship, and the other directly uses stellar masses estimated from near-infrared observations. The fgas–λEdd correlation we found concurs with the cosmic decreasing trend in λEdd, as cold molecular gas is primarily consumed by star formation. This correlation qualitatively matches predictions of recent semi-analytic models of the cosmic downsizing of SMBHs as well. As the gas mass surface density would eventually be a key parameter controlling mass accretion, we need high-resolution observations to identify further differences in the molecular properties around super-Eddington and sub-Eddington SMBHs.

【 授权许可】

CC BY