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

Shouyi Wang, Fan Zou, Chang-Hao Chen, W. N. Brandt, Elena Gallo, Bin Luo, Xue-Bing Wu, Yuming Fu, Dieu D. Nguyen, Shengxiu Sun

First listed 2026-04-29 | Last updated 2026-04-29

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] $\lambda3426$ emission, exhibiting a rest-frame equivalent width (EW) of $\approx 48$ A. We present $\sim100$ ks Nuclear Spectroscopic Telescope Array follow-up observations, confirming its heavily obscured nature with a column density (in $\mathrm{cm^{-2}}$) of $\log N_\mathrm{H} = 23.3^{+0.4}_{-1.2}$ and an intrinsic $2$--$10$ keV luminosity (in $\mathrm{erg~s^{-1}}$) of $\log L_\mathrm{X,int} = 42.92^{+0.24}_{-0.20}$. GAMA 376183 thus represents one of the few known heavily obscured AGNs in low-mass galaxies. Its estimated Eddington ratio is $λ_\mathrm{Edd}\approx0.8$, 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.

Short digest

GAMA 376183 is singled out by an exceptionally strong [Ne v] λ3426 line (rest‑frame EW ≈ 48 Å) in a low‑mass host (M* ≈ 10^10 M⊙), with consistent GAMA and DESI spectra across epochs. ~100 ks NuSTAR follow‑up confirms heavy obscuration (log N_H = 23.3^{+0.4}_{−1.2}) and an intrinsic 2–10 keV luminosity of log L_X,int = 42.92^{+0.24}_{−0.20}. Imaging and SED modeling reveal a disturbed, likely merging system with subcomponents (C1–C3) and a recent starburst, while the inferred Eddington ratio λ_Edd ≈ 0.8 signals rapid black‑hole growth. Together, these point to merger‑triggered, Eddington‑limited accretion in a rare low‑mass case and showcase [Ne v] as an efficient selector of heavily obscured low‑mass AGN.

Key figures to inspect

• Figure 1: Use the [Ne v] λ3426 zoom‑in and two‑Gaussian fit to verify the extreme EW and line width; compare GAMA vs DESI spectra to confirm the stated lack of variability across epochs.
• Figure 2: Locate GAMA 376183 on the Kewley‑demarcated BPT plane to see that AGN ionization dominates over any starburst contribution implied by the SED.
• Figure 3: Inspect the HSC multiband decomposition and residual maps to identify disturbed structure and the C1–C3 subcomponents; check how disk/bulge subtraction and the radial profile support a merger interpretation.
• Figure 4: Examine the CIGALE SED decomposition to gauge AGN vs host contributions and the recent‑burst component; compare sfhdelayedbq vs sfhdelayed fits for burst age and IR energy balance.