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1. A Rapidly Accreting Active Galactic Nucleus Hidden in a Dust-obscured Galaxy at z ∼ 0.8

   https://doi.org/10.3847/1538-4357/ad8c3f  

   Cristello, Nathan; Zou, Fan; Brandt, William N; Yu, Zhibo; Vito, Fabio; Zhu, Shifu (December 2024, The Astrophysical Journal)

   Abstract Dust-obscured galaxies (DOGs) containing central supermassive black holes (SMBHs) that are rapidly accreting (i.e., having high Eddington ratios,λ_Edd) may represent a key phase closest to the peak of both the black hole and galaxy growth in the coevolution framework for SMBHs and galaxies. In this work, we present a 68 ks XMM-Newton observation of the high-λ_EddDOG J1324+4501 atz∼ 0.8, which was initially observed by Chandra. We analyze the XMM-Newton spectra jointly with archival Chandra spectra. In performing a detailed X-ray spectral analysis, we find that the source is intrinsically X-ray luminous with $\log (L_{\mathrm{X}}$ /erg ${\mathrm{s}}^{-1})={44.71}_{-0.12}^{+0.08}$ and heavily obscured with $\log \left(N_{\mathrm{H}}/{\mathrm{cm}}^{-2}\right)={23.43}_{-0.13}^{+0.09}$ . We further utilize UV-to-IR archival photometry to measure and fit the source’s spectral energy distribution to estimate its host-galaxy properties. We present a supplementary comparison sample of 21 X-ray luminous DOGs from the XMM-SERVS survey with sufficient (>200) 0.5–10 keV counts to perform a similarly detailed X-ray spectral analysis. Of the X-ray luminous DOGs in our sample, we find that J1324+4501 is the most remarkable, possessing one of the highest X-ray luminosities, column densities, and star formation rates. We demonstrate that J1324+4501 is in an extreme evolutionary stage where SMBH accretion and galaxy growth are at their peaks. 

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2. Investigating the Star Formation Rates of Active Galactic Nucleus Hosts Relative to the Star-forming Main Sequence

   https://doi.org/10.3847/1538-4357/ad2177  

   Cristello, Nathan; Zou, Fan; Brandt, W N; Chen, Chien-Ting J; Leja, Joel; Ni, Qingling; Yang, Guang (February 2024, The Astrophysical Journal)

   Abstract A fundamental question in galaxy and black hole evolution remains how galaxies and their supermassive black holes have evolved together over cosmic time. Specifically, it is still unclear how the position of X-ray active galactic nucleus (AGN) host galaxies with respect to the star-forming main sequence (MS) may change with the X-ray luminosity (L_X) of the AGN or the stellar mass (M_⋆) of the host galaxy. We use data from the XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS) to probe this issue. XMM-SERVS is covered by the largest medium-depth X-ray survey (with superb supporting multiwavelength data) and thus contains the largest sample to date for study. To ensure consistency, we locally derive the MS from a large reference galaxy sample. In our analysis, we demonstrate that the turnover of the galaxy MS does not allow reliable conclusions to be drawn for high-mass AGNs, and we establish a robust safe regime where the results do not depend upon the choice of MS definition. Under this framework, our results indicate that less massive AGN host galaxies ( $\log M_{\star }\sim 9.5–10.5M_{\odot }$ ) generally possess enhanced star formation rates compared to their normal-galaxy counterparts while the more massive AGN host galaxies ( $\log M_{\star }\sim 10.5–11.5M_{\odot }$ ) lie on or below the star-forming MS. Further, we propose an empirical model for how the placement of an AGN with respect to the MS (SFR_norm) evolves as a function of bothM_⋆andL_X. 

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3. 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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4. The X-Ray Link between High Eddington Ratio Dust-obscured Galaxies (DOGs) and Hot DOGs

   https://doi.org/10.3847/1538-4357/adf55c  

   Zou, Fan; Brandt, W N; Gallo, Elena; Vito, Fabio; Yu, Zhibo (September 2025, The Astrophysical Journal)

   Abstract Dust-obscured galaxies (DOGs) with extremely red optical-to-infrared colors are often associated with intense starburst and active galactic nucleus (AGN) activity. Studying DOGs can provide insights into the processes that drive the growth of galaxies and their central supermassive black holes. However, the general DOG population is heterogeneous, spanning a wide range of evolutionary stages, and has X-ray obscuring column densities (N_H) covering low to high levels. In this work, we focus on seven high Eddington ratio DOGs ( $\log {\lambda }_{\mathrm{Edd}}\gtrsim -0.5$ ) to examine their X-ray obscuration properties using new and archival X-ray observations. We confirm that these systems are generally heavily obscured, with six out of seven havingN_H ≳ 10²³cm⁻²and three out of seven havingN_H ≳ 10²⁴cm⁻². Based on the observed similarity with the rare Hot DOG population, we argue that both high-λ_EddDOGs and Hot DOGs likely trace the postmerger phase, during which AGNs are enshrouded by large columns of dust-rich material. 

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5. Accretion History of AGNs: A Multiwavelength Comparison of X-Ray- and Infrared-selected AGNs

   https://doi.org/10.3847/1538-4357/ae2a32  

   Kelly, Thresa; Auge, Connor; Sanders, David; Kirkpatrick, Allison; Carroll, Christopher M; Urry, C Megan; Cappelluti, Nico; Ananna, Tonima Tasnim; Baloković, Mislav; Boquien, Médéric; et al (January 2026, The Astrophysical Journal)

   Abstract Identifying active galactic nuclei (AGNs) using only one wavelength region may miss AGNs with characteristics unfavorable for the identification method, which introduces bias in the sample. To better understand these selection effects, we compare the multiwavelength properties of 2584 X-ray- and IR-selected AGNs atz < 3 in the COSMOS field. The X-ray-selected sample consists of the 2219 AGNs with intrinsic 0.5–10 keV X-ray luminosity greater than 10⁴³erg s⁻¹; the 993 IR-selected AGNs are identified by their high-contrast, power-law IR colors using Spitzer/IRAC observations. We find that both selection methods miss a significant fraction of AGNs, as only 24.3% of AGNs (628 out of the total of 2584 AGNs) are recovered by both selection criteria. X-ray selection can capture the most diverse range of multiwavelength spectral emission features, while IRAC selection is biased against AGNs with a steeply decreasing power flux (λF_λ) between 1 and 6μm. For AGNs with X-ray detections, IRAC-selected sources are 2.5× more X-ray luminous than AGNs not identified by their IR colors. IRAC-selected AGNs without detectable X-rays are obscured, as they have a mean X-ray correction factor $\log (L_{\mathrm{X},\mathrm{obs}}/L_{\mathrm{X},\mathrm{int}})=$ −1.4; 28.5%–42.2% of these AGNs are Compton-thick (according to estimated column densities). Only 1.4% of X-ray-selected AGNs are Compton-thick. The AGN selection technique used significantly impacts the overall characteristics of the resulting AGN sample. 

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