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1. CLEAR: Spatially Resolved Emission Lines and Active Galactic Nuclei at 0.6 < z < 1.3

   https://doi.org/10.3847/1538-4357/aca668  

   Backhaus, Bren E.; Bridge, Joanna S.; Trump, Jonathan R.; Cleri, Nikko J.; Papovich, Casey; Simons, Raymond C.; Momcheva, Ivelina; Holwerda, Benne W.; Ji, Zhiyuan; Jung, Intae; et al (January 2023, The Astrophysical Journal)

   Abstract We investigate spatially resolved emission-line ratios in a sample of 219 galaxies (0.6 < z < 1.3) detected using the G102 grism on the Hubble Space Telescope Wide Field Camera 3 taken as part of the CANDELS Ly α Emission at Reionization survey to measure ionization profiles and search for low-luminosity active galactic nuclei (AGN). We analyze [O iii ] and H β emission-line maps, enabling us to spatially resolve the [O iii ]/H β emission-line ratio across the galaxies in the sample. We compare the [O iii ]/H β ratio in galaxy centers and outer annular regions to measure ionization differences and investigate the potential of sources with nuclear ionization to host AGN. We investigate some of the individual galaxies that are candidates to host strong nuclear ionization and find that they often have low stellar mass and are undetected in X-rays, as expected for low-luminosity AGN in low-mass galaxies. We do not find evidence for a significant population of off-nuclear AGN or other clumps of off-nuclear ionization. We model the observed distribution of [O iii ]/H β spatial profiles and find that most galaxies are consistent with a small or zero difference between their nuclear and off-nuclear line ratios, but 6%–16% of galaxies in the sample are likely to host nuclear [O iii ]/H β that is ∼0.5 dex higher than in their outer regions. This study is limited by large uncertainties in most of the measured [O iii ]/H β spatial profiles; therefore, deeper data, e.g., from deeper HST/WFC3 programs or from JWST/NIRISS, are needed to more reliably measure the spatially resolved emission-line conditions of individual high-redshift galaxies. 

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2. The Lick AGN Monitoring Project 2016: Dynamical Modeling of Velocity-resolved Hβ Lags in Luminous Seyfert Galaxies

   https://doi.org/10.3847/1538-4357/ac6171  

   Villafaña, Lizvette; Williams, Peter R.; Treu, Tommaso; Brewer, Brendon J.; Barth, Aaron J.; U, Vivian; Bennert, Vardha N.; Alexander Vogler, H.; Guo, Hengxiao; Bentz, Misty C.; et al (May 2022, The Astrophysical Journal)

   Abstract We have modeled the velocity-resolved reverberation response of the H β broad emission line in nine Seyfert 1 galaxies from the Lick Active Galactic Nucleus (AGN) Monitoring Project 2016 sample, drawing inferences on the geometry and structure of the low-ionization broad-line region (BLR) and the mass of the central supermassive black hole. Overall, we find that the H β BLR is generally a thick disk viewed at low to moderate inclination angles. We combine our sample with prior studies and investigate line-profile shape dependence, such as log 10 ( FWHM / σ ) , on BLR structure and kinematics and search for any BLR luminosity-dependent trends. We find marginal evidence for an anticorrelation between the profile shape of the broad H β emission line and the Eddington ratio, when using the rms spectrum. However, we do not find any luminosity-dependent trends, and conclude that AGNs have diverse BLR structure and kinematics, consistent with the hypothesis of transient AGN/BLR conditions rather than systematic trends. 

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3. Nuclear Spectral Energy Distributions of Luminous Infrared Galaxies

   https://doi.org/10.3847/1538-4357/add0b2  

   Gao, Tianmu; U, Vivian; Auge, Connor W; Song, Yiqing; Linden, Sean T; Iwasawa, Kazushi; Peca, Alessandro; Privon, George C; Sanders, David B; Torres-Albà, Núria; et al (July 2025, The Astrophysical Journal)

   Abstract We present nuclear (100–150 pc) spectral energy distributions (SEDs) for a sample of 23 nearby luminous infrared galaxies hosting a total of 28 nuclei. We gather aperture photometry from high-resolution X-ray to submillimeter data for each nuclear region localized by Atacama Large Millimeter/submillimeter Array observations of the dust continuum. We model the broadband SEDs using X-CIGALE. Binning the merging systems by interaction class, we find that the active galactic nucleus (AGN) fraction (fraction of AGN infrared luminosity to total infrared luminosity) appears enhanced in the late- and post-merger stages compared to the early-merger stage. Examining the relationship between X-ray emission and infrared emission of the nuclear regions, we find that the infrared emission in the nuclei is dominated by dust and AGNs, with minimal contribution from stars. We also find that nuclear regions have higher X-ray hardness ratios than the host galaxies globally among both the AGN and non-AGN population. We highlight the similarities and differences in the SEDs of dual nuclei in five closely separated late-stage merging systems: Arp 220 (d_nuc ∼ 0.5 kpc), NGC 6240 (d_nuc ∼ 1 kpc), IRAS 07251−0248 (d_nuc ∼ 2 kpc), IRAS F12112+0305 (d_nuc ∼ 4 kpc), and IRAS F14348+1447 (d_nuc ∼ 6 kpc). The SEDs for these resolved pairs are distinct, suggesting that the AGN state is much more susceptible to the stellar and dust content within the immediate circumnuclear (<150 pc) environment than to the host’s global infrared luminosity or merger stage. 

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4. A cosmic UV/X-ray background model update

   https://doi.org/10.1093/mnras/staa302  

   Faucher-Giguère, Claude-André (April 2020, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We present an updated model of the cosmic ionizing background from the UV to the X-rays. Relative to our previous model, the new model provides a better match to a large number of up-to-date empirical constraints, including: (1) new galaxy and AGN luminosity functions; (2) stellar spectra including binary stars; (3) obscured and unobscured AGN; (4) a measurement of the non-ionizing UV background; (5) measurements of the intergalactic H i and He ii photoionization rates at z ∼ 0−6; (6) the local X-ray background; and (7) improved measurements of the intergalactic opacity. In this model, AGN dominate the H i ionizing background at z ≲ 3 and star-forming galaxies dominate it at higher redshifts. Combined with the steeply declining AGN luminosity function beyond z ∼ 2, the slow evolution of the H i ionization rate inferred from the high-redshift H i Ly α forest requires an escape fraction from star-forming galaxies that increases with redshift (a population-averaged escape fraction of $$\approx 1{{\ \rm per\ cent}}$$ suffices to ionize the intergalactic medium at z = 3 when including the contribution from AGN). We provide effective photoionization and photoheating rates calibrated to match the Planck 2018 reionization optical depth and recent constraints from the He ii Ly α forest in hydrodynamic simulations. 

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5. Cosmological-scale Lyα Forest Absorption around Galaxies and AGNs Probed with the HETDEX and SDSS Spectroscopic Data

   https://doi.org/10.3847/1538-4357/accf88  

   Sun, Dongsheng; Mawatari, Ken; Ouchi, Masami; Ono, Yoshiaki; Yajima, Hidenobu; Zhang, Yechi; Abe, Makito; Bowman, William P; Cooper, Erin Mentuch; Davis, Dustin; et al (June 2023, The Astrophysical Journal)

   Abstract We present cosmological-scale three-dimensional neutral hydrogen (Hi) tomographic maps atz= 2–3 over a total of 837 deg²in two blank fields that are developed with Lyαforest absorptions of 14,736 background Sloan Digital Sky Survey (SDSS) quasars atz= 2.08–3.67. Using the tomographic maps, we investigate the large-scale (≳10h⁻¹cMpc) average Hiradial profiles and two-direction profiles of the line-of-sight (LOS) and transverse directions around galaxies and active galactic nuclei (AGNs) atz= 2–3 identified by the Hobby–Eberly Telescope Dark Energy eXperiment survey and SDSS, respectively. The peak of the Hiradial profile around galaxies is lower than the one around AGNs, suggesting that the dark matter halos of galaxies are less massive on average than those of AGNs. The LOS profile of AGNs is narrower than the transverse profile, indicating the Kaiser effect. There exist weak absorption outskirts at ≳30h⁻¹cMpc beyond Histructures of galaxies and AGNs found in the LOS profiles that can be explained by the Higas at ≳30h⁻¹cMpc falling toward the source position. Our findings indicate that the Hiradial profile of AGNs has transitions from proximity zones (≲a fewh⁻¹cMpc) to the Histructures (∼1–30h⁻¹cMpc) and the weak absorption outskirts (≳30h⁻¹cMpc). Although there is no significant dependence of AGN types (type 1 vs. type 2) on the Hiprofiles, the peaks of the radial profiles anticorrelate with AGN luminosities, suggesting that AGNs’ ionization effects are stronger than the gas mass differences. 

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