X-ray AGNs with SRG/eROSITA: Multi-wavelength observations reveal merger triggering and post-coalescence circumnuclear blowout
arxiv(2024)
摘要
Major mergers between galaxies are predicted to fuel their central
supermassive black holes (SMBHs), particularly after coalescence. However,
determining the prevalence of active galactic nuclei (AGNs) in mergers remains
a challenge, because AGN diagnostics are sensitive to details of the central
structure (e.g., nuclear gas clouds, geometry and orientation of a dusty torus)
that are partly decoupled from SMBH accretion. X-rays, expected to be
ubiquitous among accreting systems, are detectable through non-Compton-thick
screens of obscuring material, and thus offer the potential for a more complete
assessment of AGNs in mergers. But, extant statistical X-ray studies of AGNs in
mergers have been limited by either sparse, heterogeneous, or shallow on-sky
coverage. We use new X-ray observations from the first SRG/eROSITA all-sky data
release to characterize the incidence, luminosity, and observability of AGNs in
mergers. Combining machine learning and visual classification, we identify 923
post-mergers in Dark Energy Camera Legacy Survey (DECaLS) imaging and select
4,565 interacting galaxy pairs (with separations <120 kpc and mass ratios
within 1:10) from the Sloan Digital Sky Survey. We find that galaxies with
X-ray AGNs are 2.0+/-0.24 times as likely to be identified as post-mergers
compared to non-AGN controls, and that post-mergers are 1.8+/-0.1 times as
likely to host an X-ray AGN as non-interacting controls. A multi-wavelength
census of X-ray, optical, and mid-IR-selected AGNs suggests a picture wherein
the underlying AGN fraction increases during pair-phase interactions, that
galaxy pairs within 20 kpc become heavily obscured, and that the obscuration
often clears post-coalescence.
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