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1. Magellan Spectroscopy of Active Galactic Nuclei in Low-mass Galaxies: Scaling Relations and a Triple-peaked Active Galactic Nucleus

   https://doi.org/10.3847/1538-4357/aded92  

   Sturm, Megan R; Reines, Amy E; Greene, Jenny; Salehirad, Sheyda (August 2025, The Astrophysical Journal)

   Abstract In this work, we aim to further populate the low-mass regime of black hole (BH) scaling relations to better understand the formation and growth mechanisms of central supermassive BHs. We target six galaxies that have been previously identified as hosting active galactic nuclei (AGNs) based on optical spectroscopy from the Galaxy and Mass Assembly survey or the Sloan Digital Sky Survey with stellar masses reported to beM_⋆ < 5 × 10⁹M_⊙. Using follow-up optical spectroscopy from the Magellan Echellette Spectrograph, we extract galaxy velocity dispersions (σ_⋆) and estimate virial BH masses from broad Hαemission. We find that the galaxies in our sample do not deviate significantly from either theM_BH−σ_*orM_BH−M_*scaling relations defined by higher-mass galaxies. Additionally, we identify one galaxy with triple-peaked [SII], [NII], Hα, and Hβemission lines. This spectral shape is not shared by [OIII] and, in fact, the [OIII] line appears to have distinct kinematics from the other emission lines. Incorporating the spatial distribution of the various emission lines, we find that the galaxy spectrum is consistent with a prominent central AGN driving an outflow, surrounded by an extended ring/disk of gas predominantly ionized by shocks and/or star formation. This work has implications for the demographics of BHs in low-mass galaxies and the role of AGN feedback. 

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2. Shocked POststarburst Galaxy Survey. IV. Outflows in Shocked Poststarburst Galaxies Are Not Responsible for Quenching

   https://doi.org/10.3847/1538-4357/ad900f  

   Fodor, Antoniu; Tomko, Taylor; Braun, Mary; Medling, Anne M; Johnson, Thomas M; Thompson, Alexander; Johnston, Victor D; Newhouse, Matthew; Luo, Yuanze; French, K Decker; et al (January 2025, The Astrophysical Journal)

   Abstract Shocked POstarburst Galaxies (SPOGs) exhibit both emission lines suggestive of shock-heated gas and poststarburst-like stellar absorption, resulting in a unique subset for galaxy evolution studies. We have observed 77 galaxies that fulfilled the SPOG criteria selection using the DeVeny Spectrograph on the Lowell Discovery Telescope. Our long-slit minor axis spectra detect Hαand [OIII] in some SPOGs out to 6 kpc above the galactic plane. We find extraplanar ionized gas in 31 targets of our sample overall. Using their internal and external kinematics, we argue that 22 galaxies host outflows with ionized gas masses ranging from 10²M_⊙to 10⁵M_⊙. The rest are likely extended diffuse ionized gas. A positive correlation exists between active galactic nuclei (AGN) luminosity and the extraplanar gas extent, velocity dispersion, and mass—suggesting that the AGN may indeed drive the outflows detected in AGN hosts. The low masses of the extraplanar gas suggest that these outflows are not depleting each galaxy’s gas reserves. The outflows, therefore, are not likely a significant quenching mechanism in these SPOGs. 

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3. The Outflowing [O ii] Nebulae of Compact Starburst Galaxies at z ∼ 0.5

   https://doi.org/10.3847/1538-4357/ad7b0c  

   Perrotta, Serena; Coil, Alison L; Rupke, David_S N; Ning, Wenmeng; Duong, Brendan; Diamond-Stanic, Aleksandar M; Fielding, Drummond B; Geach, James E; Hickox, Ryan C; Moustakas, John; et al (November 2024, The Astrophysical Journal)

   Abstract High-velocity outflows are ubiquitous in compact, massive (M_*∼ 10¹¹M_⊙),z∼ 0.5 galaxies with extreme star formation surface densities (Σ_SFR∼ 2000M_⊙yr⁻¹kpc⁻²). We have previously detected and characterized these outflows using Mgiiabsorption lines. To probe their full extent, we present Keck/KCWI integral field spectroscopy of the [Oii] and Mgiiemission nebulae surrounding all of the 12 galaxies in this study. We find that [Oii] is more effective than Mgiiin tracing low surface brightness, extended emission in these galaxies. The [Oii] nebulae are spatially extended beyond the stars, with radial extentR₉₀between 10 and 40 kpc. The nebulae exhibit nongravitational motions, indicating galactic outflows with maximum blueshifted velocities ranging from −335 to −1920 km s⁻¹. The outflow kinematics correlate with the bursty star formation histories of these galaxies. Galaxies with the most recent bursts of star formation (within the last <3 Myr) exhibit the highest central velocity dispersions (σ≳ 400 km s⁻¹), while the oldest bursts have the lowest-velocity outflows. Many galaxies exhibit both high-velocity cores and more extended, slower-moving gas indicative of multiple outflow episodes. The slower, larger outflows occurred earlier and have decelerated as they propagate into the circumgalactic medium and mix on timescales ≳50 Myr. 

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4. Kinematics, Structure, and Mass Outflow Rates of Extreme Starburst Galactic Outflows

   https://doi.org/10.3847/1538-4357/acc660  

   Perrotta, Serena; Coil, Alison L.; Rupke, David S.; Tremonti, Christy A.; Davis, Julie D.; Diamond-Stanic, Aleksandar M.; Geach, James E.; Hickox, Ryan C.; Moustakas, John; Rudnick, Gregory H.; et al (May 2023, The Astrophysical Journal)

   Abstract We present results on the properties of extreme gas outflows in massive (M_*∼ 10¹¹M_⊙), compact, starburst (star formation rate, SFR∼ 200M_⊙yr⁻¹) galaxies atz= 0.4–0.7 with very high star formation surface densities (Σ_SFR∼ 2000M_⊙yr⁻¹kpc⁻²). Using optical Keck/HIRES spectroscopy of 14 HizEA starburst galaxies, we identify outflows with maximum velocities of 820–2860 km s⁻¹. High-resolution spectroscopy allows us to measure precise column densities and covering fractions as a function of outflow velocity and characterize the kinematics and structure of the cool gas outflow phase (T∼ 10⁴K). We find substantial variation in the absorption profiles, which likely reflects the complex morphology of inhomogeneously distributed, clumpy gas and the intricacy of the turbulent mixing layers between the cold and hot outflow phases. There is not a straightforward correlation between the bursts in the galaxies’ star formation histories and their wind absorption line profiles, as might naively be expected for starburst-driven winds. The lack of strong Mgiiabsorption at the systemic velocity is likely an orientation effect, where the observations are down the axis of a blowout. We infer high mass outflow rates of ∼50–2200M_⊙yr⁻¹, assuming a fiducial outflow size of 5 kpc, and mass loading factors ofη∼ 5 for most of the sample. While these values have high uncertainties, they suggest that starburst galaxies are capable of ejecting very large amounts of cool gas that will substantially impact their future evolution. 

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5. A Rare Eddington-limited, Heavily Obscured Low-mass Active Galactic Nucleus Likely Triggered by a Galaxy Merger

   https://doi.org/10.3847/1538-4357/ae6779  

   Wang, Shouyi; Zou, Fan; Chen, Chang-Hao; Brandt, W N; Gallo, Elena; Luo, Bin; Wu, Xue-Bing; Fu, Yuming; Nguyen, Dieu D; Sun, Shengxiu (May 2026, The Astrophysical Journal)

   Abstract We report a detailed analysis of GAMA 376183, a powerful, heavily obscured active galactic nucleus (AGN) hosted by a low-mass galaxy (M_⋆ ≈ 10¹⁰M_⊙) likely experiencing a galaxy merger. The source was initially identified due to its remarkably strong [Nev]λ3426 emission, exhibiting a rest-frame equivalent width of ≈48 Å. We present ∼100 ks Nuclear Spectroscopic Telescope Array (or NuSTAR) follow-up observations, confirming its heavily obscured nature with a column density (in cm⁻²) of $\log N_{\mathrm{H}}=23.3_{-1.2}^{+0.4}$ and an intrinsic 2–10 keV luminosity (in erg 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 isλ_Edd ≈ 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) [Nev] 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. 

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