Active Galactic Nuclei and Host Galaxies in COSMOS-Web. II. First Look at the Kpc-scale Dual and Offset AGN Population
arxiv(2024)
摘要
Kpc-scale dual and offset Active Galactic Nuclei (AGNs) are signposts of
accreting supermassive black holes (SMBHs) triggered during late-stage galaxy
mergers, offering crucial insights into the coevolution of SMBHs and galaxies.
However, robustly confirmed systems at high redshift (e.g., z>1) are scarce
and biased towards the most luminous and unobscured systems. In this study, we
systematically search for kpc-scale (projected separation <15 kpc) dual and
offset AGNs around 571 moderate-luminosity, X-ray-selected AGNs including the
obscured population, utilizing deep HST ACS/F814W and multiband JWST NIRCam
imaging from the COSMOS-Web survey. We identify 59 dual and 30 offset AGN
candidates in late stage major mergers based on spatially-resolved spectral
energy distribution analyses. This translates to ∼28 and ∼10
bona-fide dual and offset AGNs using a probabilistic pair counting scheme to
minimize chance superpositions. Notably, the fraction of dual and offset AGNs
among moderate-luminosity (L_ bol∼10^43-10^46 erg s^-1),
obscured AGNs is nearly two orders of magnitude higher than that of the most
luminous, unobscured quasar pairs. We find tentative evidence for an increasing
pair fraction among AGNs with redshift (from a few percent at z∼ 0.5 to
∼22.9_-17.7^+27.5% at z∼4.5) and a higher occurrence rate of
dual over offset AGNs. There is no pileup of dual/offset AGNs below ∼
2 kpc separations. These results generally align with predictions from
the ASTRID and Horizon-AGN cosmological simulations when matching sample
selection criteria, implying a high probability of both BHs being active
simultaneously in late-stage major mergers.
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