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1. 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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2. GOALS-JWST: Tracing AGN Feedback on the Star-forming Interstellar Medium in NGC 7469

   https://doi.org/10.3847/2041-8213/ac9ebf  

   Lai, Thomas S.-Y.; Armus, Lee; U, Vivian; Díaz-Santos, Tanio; Larson, Kirsten L.; Evans, Aaron; Malkan, Matthew A.; Appleton, Philip; Rich, Jeff; Müller-Sánchez, Francisco; et al (December 2022, The Astrophysical Journal Letters)

   Abstract We present James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) integral-field spectroscopy of the nearby merging, luminous infrared galaxy, NGC 7469. This galaxy hosts a Seyfert type-1.5 nucleus, a highly ionized outflow, and a bright, circumnuclear star-forming ring, making it an ideal target to study active galactic nucleus (AGN) feedback in the local universe. We take advantage of the high spatial/spectral resolution of JWST/MIRI to isolate the star-forming regions surrounding the central active nucleus and study the properties of the dust and warm molecular gas on ∼100 pc scales. The starburst ring exhibits prominent polycyclic aromatic hydrocarbon (PAH) emission, with grain sizes and ionization states varying by only ∼30%, and a total star formation rate of 10–30 M ⊙ yr −1 derived from fine structure and recombination emission lines. Using pure rotational lines of H 2 we detect 1.2 × 10 7 M ⊙ of warm molecular gas at a temperature higher than 200 K in the ring. All PAH bands get significantly weaker toward the central source, where larger and possibly more ionized grains dominate the emission, likely the result of the ionizing radiation and/or the fast wind emerging from the AGN. The small grains and warm molecular gas in the bright regions of the ring however display properties consistent with normal star-forming regions. These observations highlight the power of JWST to probe the inner regions of dusty, rapidly evolving galaxies for signatures of feedback and inform models that seek to explain the coevolution of supermassive black holes and their hosts. 

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3. Radio spectral energy distribution of low- z metal-poor extreme starburst galaxies: novel insights on the escape of ionizing photons

   https://doi.org/10.1093/mnras/stag492  

   Bait, Omkar; Schaerer, Daniel; Izotov, Yuri I; Sebastian, Biny (April 2026, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Recent optical surveys have identified a rare population of low-z ($$z \sim 0.01 \!-\! 0.06$$) extreme star-forming galaxies (xSFGs) characterized by very low metallicity, strong emission lines, extremely high specific star-formation rate, low stellar mass, and strong Ly $$\alpha$$ emission. Their global properties resemble recently discovered $$z\gt 6$$ reionization-era star-forming galaxies. We present new multifrequency radio continuum observations of eight xSFGs using the upgraded Giant Metrewave Radio Telescope at 1.25 GHz, the Karl G. Jansky Very Large Array at $1.5, 3.0, 6.0, 10.0$, and 15.0 GHz, along with archival LOw Frequency ARray data at 150 MHz for several sources. These data allow construction of the radio spectral energy distribution (radio-SED) from $$\sim 1$$ GHz (down to 150 MHz for some sources) to 15 GHz, spanning nearly two orders of magnitude in frequency. We find that xSFGs exhibit a flat spectral index between 6 and 15 GHz, while a subset shows spectral turnovers at $$0.3 \!-\! 3$$ GHz. Our Bayesian radio-SED modelling indicates that these features are consistent with a high thermal fraction combined with free–free absorption, requiring high emission measures in some systems. By comparing modelled thermal radio emission with observed H$$\beta {}$$ line flux density, we find evidence for dust in several xSFGs. Finally, we confirm a previously reported correlation between Lyman continuum escape fraction ($$f_\mathrm{esc}^\mathrm{LyC}$$), ionization state, and radio spectral index, particularly among strong leakers. 

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4. ALMA characterizes the dust temperature of z ∼ 5.5 star-forming galaxies

   https://doi.org/10.1093/mnras/staa2545  

   Faisst, Andreas L; Fudamoto, Yoshinobu; Oesch, Pascal A; Scoville, Nick; Riechers, Dominik A; Pavesi, Riccardo; Capak, Peter (September 2020, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT The infrared (IR) spectral energy distributions (SEDs) of main-sequence galaxies in the early Universe (z > 4) is currently unconstrained as IR continuum observations are time-consuming and not feasible for large samples. We present Atacama Large Millimetre Array Band 8 observations of four main-sequence galaxies at z ∼ 5.5 to study their IR SED shape in detail. Our continuum data (rest-frame 110 $$\rm \mu m$$, close to the peak of IR emission) allows us to constrain luminosity-weighted dust temperatures and total IR luminosities. With data at longer wavelengths, we measure for the first time the emissivity index at these redshifts to provide more robust estimates of molecular gas masses based on dust continuum. The Band 8 observations of three out of four galaxies can only be reconciled with optically thin emission redward of rest-frame $$100\, {\rm \mu m}$$. The derived dust peak temperatures at z ∼ 5.5 ($$30\!-\!43\, {\rm K}$$) are elevated compared to average local galaxies, however, $$\sim 10\, {\rm K}$$ below what would be predicted from an extrapolation of the trend at z < 4. This behaviour can be explained by decreasing dust abundance (or density) towards high redshifts, which would cause the IR SED at the peak to be more optically thin, making hot dust more visible to the external observer. From the $$850{\hbox{-}}{\rm \mu m}$$ dust continuum, we derive molecular gas masses between 1010 and $$10^{11}\, {\rm M_{\odot }}$$ and gas fractions (gas over total mass) of $$30\!-\!80{{\ \rm per\ cent}}$$ (gas depletion times of $$100\!-\!220\, {\rm Myr}$$). All in all, our results provide a first measured benchmark SED to interpret future millimetre observations of normal, main-sequence galaxies in the early Universe. 

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5. VERITAS Observations Contemporaneous with the LHAASO Detection of NGC 4278

   https://doi.org/10.3847/1538-4357/ae5226  

   Archer, A; Bangale, P; Bartkoske, J T; Benbow, W; Buckley, J H; Chen, Y; Christiansen, J L; Chromey, A J; Duerr, A; Errando, M; et al (April 2026, The Astrophysical Journal)

   Abstract Significant gamma-ray emission between 1 TeV and 20 TeV from a point source, 1LHAASO J1219+2915, consistent with the location of the LINER/LLAGN galaxy NGC 4278 was recently reported by the Large High Altitude Air Shower Observatory (LHAASO) collaboration. These data were later split into active and quasi-quiet states, with most of the LHAASO significance coming from the active state (MJD 59449-59589). Subsequent analysis of Fermi-LAT and Swift-XRT observations have been used to explore the double-peaked broadband emission. Models of the spectral energy distribution (SED) are currently unconstrained due to the lack of contemporaneous multiwavelength data at either peak. Here, we report serendipitous observations of NGC 4278 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS), made possible by the contemporaneous observations of the nearby blazars 1ES 1218+304, 1ES 1215+303, and W Comae, each of which are located within 2° of NGC 4278. VERITAS did not detect any gamma-ray emission, and a flux upper limit was calculated. The flux upper limits constrain the photon spectrum of the quasi-quiet period, and together with Fermi-LAT, indicate a peak in the SED between 100 GeV and 2 TeV. We present an interpretation of the broadband SED that is based on acceleration of protons in the corona of the active galactic nuclei, followed byp–γinteractions and optically thinγ-ray emission. Within this framework, the implied neutrino signal is slightly below the current sensitivity of IceCube. 

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