Coevolution and Nuclear Structure in the Dwarf Galaxy POX 52 Studied by Multiwavelength Data from Radio to X-Ray

Abstract

The nearby dwarf galaxy POX 52 at z = 0.021 hosts an active galactic nucleus (AGN) with a black hole (BH) mass of M BH ∼ 105–6 M ⊙ and an Eddington ratio of ∼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 multiwavelength 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 Hubble Space Telescope images. As a result, it is found that a classical bulge component is probably present, and its mass (M 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 the Nuclear Spectroscopic Telescope Array and XMM-Newton. The X-ray spectrum can be reproduced by multicolor blackbody, warm and hot coronae, and disk and torus reflection components. Based on this, the spin is estimated to be a 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 BH–M 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.

Fast Outflows and Luminous He ii Emission in Dwarf Galaxies with Active Galactic Nuclei (AGN)

“…Specifically, hints of star formation quenching induced by AGN feedback (Penny et al 2018) and lower-thanexpectation global HI content (Bradford et al 2018) have both been reported in dwarf galaxies with AGN. Similar evidence on such feedback is also seen in several of the latest observational studies (Davis et al 2022;Kawamuro et al 2024;Yang et al 2023). From the theoretical perspective, analytic analysis (e.g., Silk 2017; Dashyan et al 2018) and new simulations (e.g., Koudmani et al 2019Koudmani et al , 2021Lanfranchi et al 2021) have all pointed out the possibly significant effects of AGN feedback in dwarfs.…”