Oral Presentation

The average SMBH accretion properties of star-forming galaxies and their cosmic evolution over 4≲z≲7.

Author(s): Suin Matsui, Kazuhiro Shimasaku, Kei Ito, Makoto Ando, Takumi Tanaka (The University of Tokyo)

Presenter: Suin Matsui (The University of Tokyo)

There is a positive correlation between the mass of SMBHs (MBH) and the stellar mass of their host galaxies (Mstar) in the local Universe, suggesting that SMBHs and galaxies have co-evolved. Studying distant galaxies is vital to understand the co-evolution process. Although it is difficult to measure MBH in distant galaxies except for quasars, its time derivative, dMBH/dt (black hole accretion rate: BHAR), is relatively easily obtained from X-ray observations. For many galaxies without individual X-ray detection, an average BHAR () can be obtained by stacking X-ray images. However, there are few studies of accretion properties for galaxies beyond z ~ 4.

In this study, we examine the average accretion properties of about 12,000 Lyman break galaxies at 4 ≲ z ≲ 7 in the COSMOS field from the Hyper Suprime-Cam Subaru Strategic Program, where the deep X-ray image of the Chandra Legacy Survey is available. We constrain the for UV-magnitude-binned subsamples by X-ray stacking. We find that both / and / (average halo accretion rate) are much lower than the corresponding mass ratios (MBH/Mstar and MBH/Mh) of local galaxies. We also compare the results with quasars' accretion properties and cosmological simulations.