A Rare Eddington-Limited, Heavily Obscured Low-Mass Active Galactic Nucleus Likely Triggered by a Galaxy Merger

Abstract

We report a detailed analysis of GAMA 376183, a powerful, heavily obscured active galactic nucleus (AGN) hosted by a low-mass galaxy ($M_{\star }\approx 10^{10}{M}_{\odot }$) likely experiencing a galaxy merger. The source was initially identified due to its remarkably strong [Ne v] $\lambda 3426$ emission, exhibiting a rest-frame equivalent width (EW) of $\approx 48$ A. We present $\sim 100$ ks Nuclear Spectroscopic Telescope Array follow-up observations, confirming its heavily obscured nature with a column density (in $\mathrm{c}{\mathrm{m}}^{-2}$) of $\log N_{\mathrm{H}}=23.3_{-1.2}^{+0.4}$ and an intrinsic $2$--$10$ keV luminosity (in $\mathrm{erg}{\mathrm{s}}^{-1}$) of $\log L_{\mathrm{X},\mathrm{int}}=42.92_{-0.20}^{+0.24}$. GAMA 376183 thus represents one of the few known heavily obscured AGNs in low-mass galaxies. Its estimated Eddington ratio is $\hat{I}{»}_{\mathrm{Edd}}\approx 0.8$, indicative of rapid black-hole growth. High-resolution optical images reveal a disturbed, likely merging morphology, while its multiwavelength spectral energy distribution indicates a recent starburst in its host galaxy. These pieces of evidence suggest that the ongoing merger has triggered both the heavily obscured, Eddington-limited accretion and the starburst, making GAMA 376183 a rare observed case in low-mass galaxies. Overall, this unique source demonstrates that (i) [Ne v] can help identify heavily obscured low-mass AGNs, and (ii) the merger-driven coevolution framework established for massive galaxies may also extend to low-mass galaxies.

17 pages, 6 figures. Accepted for publication in ApJ