Kavli Affiliate: Claudio Ricci
| First 5 Authors: Taiki Kawamuro, Claudio Ricci, Satoshi Yamada, Hirofumi Noda, Ruancun Li
| Summary:
The nearby dwarf galaxy POX 52 at $z = 0.021$ hosts an active galactic
nucleus (AGN) with a black-hole (BH) mass of $M_{rm BH} sim 10^{5-6} M_odot$
and an Eddington ratio of $sim$ 0.1-1. This object provides the rare
opportunity to study both AGN and host-galaxy properties in a low-mass highly
accreting system. To do so, we collected its multi-wavelength data from X-ray
to radio. First, we construct a spectral energy distribution, and by fitting it
with AGN and host-galaxy components, we constrain AGN-disk and dust-torus
components. Then, while considering the AGN-disk emission, we decompose optical
HST images. As a result, it is found that a classical bulge component is
probably present, and its mass ($M_{rm bulge}$) is consistent with an expected
value from a local relation. Lastly, we analyze new quasi-simultaneous X-ray
(0.2-30 keV) data obtained by NuSTAR and XMM-Newton. The X-ray spectrum can be
reproduced by multi-color blackbody, warm and hot coronae, and disk and torus
reflection components. Based on this, the spin is estimated to be $a_{rm spin}
= 0.998_{-0.814}$, which could suggest that most of the current BH mass was
achieved by prolonged mass accretion. Given the presence of the bulge, POX 52
would have undergone a galaxy merger, while the $M_{rm BH}$-$M_{rm bulge}$
relation and the inferred prolonged accretion could suggest that AGN feedback
occurred. Regarding the AGN structure, the spectral slope of the hot corona,
its relative strength to the bolometric emission, and the torus structure are
found to be consistent with Eddington-ratio dependencies found for nearby AGNs.
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