Kavli Affiliate: Kohei Inayoshi
| First 5 Authors: Akatoki Noboriguchi, Kohei Ichikawa, Yoshiki Toba, Tom Dwelly, Kohei Inayoshi
| Summary:
Dust-obscured galaxies (DOGs) are considered to be in a co-evolution phase,
with the associated active galactic nuclei (AGN) obscured by dust and gas.
Although the DOGs are thought to harbor rapidly growing SMBHs, their X-ray
statistical properties, crucial for understanding the properties of obscuring
gas as well as the accretion disk state and the hot electron corona around the
SMBHs, remain unexplored due to the combination of the low number density of
DOGs and the lack of X-ray surveys achieving both of the wide-area and
uniformly high-sensitivity observations. We construct a sample of
X-ray-detected DOGs in the eROSITA Final Equatorial Depth Survey (eFEDS) field
and examine their X-ray statistical properties. By using Subaru/HSC SSP,
VIKING, and WISE all-sky surveys, our results reveal the discovery of 5738
IR-bright DOGs in the footprint covered by both of the eFEDS and VIKING surveys
(60 deg^2), with 65 objects identified as X-ray-detected DOGs (eFEDS-DOGs).
Among them, 41 eFEDS-DOGs show a power-law slope in the near to mid-IR bands
(power-law DOGs), indicating dust-obscured AGN. The hydrogen column density
(N_H) suggests that eFEDS-DOGs cover even unobscured AGN, spanning 10^20 < N_H
<= 10^23. On the other hand, the majority of IR-bright DOGs are not detected by
eROSITA, suggesting that most IR-bright DOGs are heavily obscured by dust and
gas with N_H > 10^23. Therefore, eFEDS-DOGs, discovered thanks to the wide-area
survey by eROSITA, are newly found populations showing less obscured phases
among the lifetime of DOGs. Additionally, some eFEDS-DOGs exhibit deviations,
down to nearly 1.0 dex below the monochromatic luminosity at 6 micron versus
absorption-corrected intrinsic X-ray luminosity between 0.5-2 keV relation,
suggesting that it may signal high Eddington ratios reaching the Eddington
limit.
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