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Abstract Outflows and jets launched from the nuclei of galaxies emit radio synchrotron emission that can be used to study the impact of accretion energy on the host galaxy. The decades-long baseline now enabled by large radio surveys allows us to identify cases where new outflows or jets have been launched. Here, we present the results of a targeted Very Large Array program observing four poststarburst galaxies that have brightened significantly in radio emission over the past ∼20 yr. We obtain quasi-simultaneous observations in five bands (1–18 GHz) for each source. We find peaked spectral energy distributions, indicative of self-absorbed synchrotron emission. While all four sources have risen significantly over the past ∼20 yr in the 1–2 GHz band, two also show clear recent flares in the 2–4 GHz band. These sources are less luminous than typical peaked-spectrum radio active galactic nucleus (AGN). It remains unclear whether these sources are low luminosity analogs of the peaked radio AGN from accreted gas, or driven by tidal disruption events with missed optical flares. Regardless of the source of the accreted material, these newly launched outflows contain sufficient energy to drive the molecular gas outflows observed in poststarburst galaxies and to drive turbulence, suppressing star formation. 

We present a study of the linear polarization properties of radio sources within the 10 deg2. Wide Chandra Deep Field South (W-CDFS) in S-band (2–4 GHz). Our W-CDFS image has an angular resolution of 15 arcsec and a 1σ RMS in Stokes I of ≈50 μJy/beam. We detect 1920 distinct source components in Stokes I and 175 in linear polarization. We examine the polarized source counts, Faraday Rotation measures, and fractional polarization of the sources in the survey. We show that sources with a total intensity above ≈10 mJy have a mean fractional polarization value of ≈3% from modeling the polarized counts. We also calculate an estimate for the limit on the fractional polarization level of sources with a total intensity below 1 mJy (mostly star-forming galaxies) of ≲3% using stacking. The mean Faraday Rotation we measure is consistent with that due to the Milky Way. We also show that fractional polarization is correlated with in-band spectral index, consistent with a lower mean fractional polarization for the flat-spectrum population. In addition to characterizing the S-band polarization properties of sources in the W-CDFS, this study will be used to validate the shallower, but higher angular resolution S-band polarimetric information that the VLA Sky Survey will provide for the whole sky above Declination −40 degrees over the next few years. 

Abstract Feedback from active galactic nuclei (AGN) is widely acknowledged to regulate the growth of massive galaxies, though its driving mechanisms are debated. Prevailing theories suggest that AGN-driven outflows are driven either by radiation pressure acting directly on the dusty interstellar medium (ISM) or by hot winds entraining cooler ISM gas, but the relative contribution of each mechanism remains uncertain. By combining optical emission line measurements with highly ionized UV emission lines, it is possible to constrain whether the pressure source applied to ionized clouds is primarily radiation or primarily hydrodynamic, and thus constrain the dominant driver. This study presents the first multiobject analysis of far-UV spectra from galactic-scale AGN-driven outflows in obscured quasars, based on Cosmic Origins Spectrograph observations of five low-redshift targets. By comparing narrow-line region UV emission-line ratios to theoretical models that vary the importance of the two pressure sources, we find that three out of five targets fall within the radiation-pressure-dominated regime. A fourth target exhibits intermediate emission-line ratios that suggest radiation pressure and pressure from a hot wind are both dynamically important. Finally, the lowest-luminosity object in our sample may have a dynamically important hot wind component, but nondetections prevent a clear conclusion in this case. These results suggest radiation pressure dominates circumnuclear narrow-line region cloud dynamics, but pressure from a hot wind also plays a role in some cases. This is consistent with AGN feedback scenarios mediated by radiation pressure or a short-lived hot wind phase that dissipates after initially accelerating outflows. 

Abstract Outflows are one of the most spectacular mechanisms through which active galactic nuclei (AGN) impact their host galaxy, though the role of AGN-driven outflows in global star formation regulation across the galaxy population is unclear. NGC 1266 is an excellent case study for investigating outflows and star formation quenching because it is a nearby (D ∼ 30 Mpc) AGN host galaxy with an outflow driving shocks through the interstellar medium (ISM) and has recently quenched its star formation outside the nucleus. While previous works have studied the molecular outflow from its CO emission, to fully characterize the impact the outflow has on the ISM observations probing the dense, cold gas are necessary. Our Atacama Large Millimeter/submillimeter Array Cycle 0 observations do not detect a molecular outflow in¹³CO(2–1) and yield a lower limit of¹²CO/¹³CO ≥ 250, suggesting a highly optically thin CO outflow with low¹³CO abundance. In contrast, we detect substantial HCN(1–0) emission in the outflow, with an HCN(1–0)/¹²CO(1–0) ratio of 0.09, consistent with global measurements of many star-forming galaxies and luminous infrared galaxies. We conclude that the CO emission traces a diffuse component of the molecular gas with a low optical depth, whereas the HCN(1–0) traces dense clumps of gas entrained in the outflow. We measure an upper limit molecular outflow rate of <85M_⊙yr^–1. Assuming the ongoing nuclear star formation and outflow continue at the same rates, NGC 1266 will deplete its gas reservoir in 450 Myr or longer, indicating that relatively low-level AGN feedback is capable of gradually expelling the molecular gas reservoir after a rapid quenching event. 

Abstract We present the CO(1–0) maps of 28 infrared-bright galaxies from the Great Observatories All-Sky Luminous Infrared Galaxy Survey (GOALS) taken with the Combined Array for Research in Millimeter Astronomy (CARMA). We detect 100 GHz continuum in 16 of the 28 CARMA GOALS galaxies, which trace both active galactic nuclei (AGNs) and compact star-forming cores. The GOALS galaxies show a variety of molecular gas morphologies, though in the majority of cases the average velocity fields show a gradient consistent with rotation. We fit the full continuum spectral energy distributions (SEDs) of each of the sources using eithermagphysor SED3FIT (if there are signs of an AGN) to derive the total stellar mass, dust mass, and SFRs of each object. We adopt a value determined from luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) ofα_CO= ${1.5}_{-0.8}^{+1.3}$ M_⊙(K km s⁻¹pc²)⁻¹, which leads to more physical values forf_moland the gas-to-dust ratio. Mergers tend to have the highest gas-to-dust ratios. We assume the cospatiality of the molecular gas and star formation and plot the CARMA GOALS sample on the Schmidt–Kennicutt relation, where we find that they preferentially lie above the line set by normal star-forming galaxies. This hyper-efficiency is likely due to the increased turbulence in these systems, which decreases the freefall time compared to star-forming galaxies, leading to “enhanced” star formation efficiency. Line wings are present in a non-negligible subsample (11/28) of the CARMA GOALS sources and are likely due to outflows driven by AGNs or star formation, gas inflows, or additional decoupled gas components. 

Abstract We present a catalog of multi-band forced photometry in the CDFS and XMM-LSS fields. We used The Tractor image-modeling software to produce de-blended photometry across 13 to 15 optical/infrared bands and determine photometric redshifts. Our catalog, which is publicly available on IRSA, contains ∼1.5 million sources and covers a total area of ∼9 deg 2 . 

Abstract Kiloparsec-scale triple active galactic nuclei (AGNs), potential precursors of gravitationally bound triple massive black holes (MBHs), are rarely seen objects and believed to play an important role in the evolution of MBHs and their host galaxies. In this work we present a multiband (3.0, 6.0, 10.0, and 15.0 GHz), high-resolution radio imaging of the triple AGN candidate, SDSS J0849+1114, using the Very Large Array. Two of the three nuclei (A and C) are detected at 3.0, 6.0, and 15 GHz for the first time, both exhibiting a steep spectrum over 3–15 GHz (with a spectral index −0.90 ± 0.05 and −1.03 ± 0.04) consistent with a synchrotron origin. Nucleus A, the strongest nucleus among the three, shows a double-sided jet, with the jet orientation changing by ∼20° between its inner 1″ and the outer 5.″5 (8.1 kpc) components, which may be explained as the MBH’s angular momentum having been altered by merger-enhanced accretion. Nucleus C also shows a two-sided jet, with the western jet inflating into a radio lobe with an extent of 1.″5 (2.2 kpc). The internal energy of the radio lobe is estimated to be 5.0 × 10 55 erg, for an equipartition magnetic field strength of ∼160 μ G. No significant radio emission is detected at all four frequencies for nucleus B, yielding an upper limit of 15, 15, 15, and 18 μ Jy beam −1 at 3.0, 6.0, 10.0, and 15.0 GHz, based on which we constrain the star formation rate in nucleus B to be ≲0.4 M ⊙ yr −1 . 

Abstract Local low-metallicity dwarf galaxies are relics of the early universe and are thought to hold clues into the origins of supermassive black holes. While recent studies are uncovering a growing population of active galactic nuclei (AGNs) in dwarf galaxies, the vast majority reside in galaxies with solar or supersolar metallicities and stellar masses comparable to that of the LMC. Using Multi-Unit Spectroscopic Explorer (MUSE) and Very Large Telescope observations, we report the detection of [Fex]λ6374 coronal line emission and a broad Hαline in the nucleus of SDSS J094401.87−003832.1, a nearby (z= 0.0049) metal-poor dwarf galaxy almost 500 times less massive than the LMC. Unlike the emission from the lower-ionization nebular lines, the [Fex]λ6374 emission is compact and centered on the brightest nuclear source, with a spatial extent of ≈100 pc, similar to that seen in well-known AGNs. The [Fex] luminosity is ≈10³⁷erg s⁻¹, within the range seen in previously identified AGNs in the dwarf-galaxy population. The [Fex] emission has persisted over the roughly 19 yr time period between the SDSS and MUSE observations, ruling out supernovae as the origin for the emission. The FWHM of the broad component of the Hαline is 446 ± 17 km s⁻¹and its luminosity is ≈1.5 × 10³⁸erg s⁻¹, corresponding to a black hole mass of ≈ 3150M_⊙, in line with its stellar mass if virial mass relations and black hole–galaxy scaling relations apply in this mass regime. These observations, together with previously reported multiwavelength observations, can most plausibly be explained by the presence of an accreting intermediate-mass black hole in a primordial galaxy analog. 

Abstract W-CDF-S, ELAIS-S1, and XMM-LSS will be three Deep-Drilling Fields (DDFs) of the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), but their extensive multiwavelength data have not been fully utilized as done in the COSMOS field, another LSST DDF. To prepare for future science, we fit source spectral energy distributions (SEDs) from X-ray to far-infrared in these three fields mainly to derive galaxy stellar masses and star formation rates. We use CIGALE v2022.0, a code that has been regularly developed and evaluated, for the SED fitting. Our catalog includes 0.8 million sources covering 4.9 deg 2 in W-CDF-S, 0.8 million sources covering 3.4 deg 2 in ELAIS-S1, and 1.2 million sources covering 4.9 deg 2 in XMM-LSS. Besides fitting normal galaxies, we also select candidates that may host active galactic nuclei (AGNs) or are experiencing recent star formation variations and use models specifically designed for these sources to fit their SEDs; this increases the utility of our catalog for various projects in the future. We calibrate our measurements by comparison with those in well-studied smaller regions and briefly discuss the implications of our results. We also perform detailed tests of the completeness and purity of SED-selected AGNs. Our data can be retrieved from a public website. 

Abstract We present an analysis of 10 ks snapshot Chandra observations of 12 shocked post-starburst galaxies, which provide a window into the unresolved question of active galactic nuclei (AGN) activity in post-starburst galaxies and its role in the transition of galaxies from active star formation to quiescence. While seven of the 12 galaxies have statistically significant detections (with two more marginal detections), the brightest only obtained 10 photons. Given the wide variety of hardness ratios in this sample, we chose to pursue a forward-modeling approach to constrain the intrinsic luminosity and obscuration of these galaxies, rather than stacking. We constrain the intrinsic luminosity of obscured power laws based on the total number of counts and spectral shape, itself mostly set by the obscuration, with hardness ratios consistent with the data. We also tested thermal models. While all the galaxies have power-law models consistent with their observations, a third of the galaxies are better fit as an obscured power law and another third are better fit as thermal emission. If these post-starburst galaxies, early in their transition, contain AGNs, then these are mostly confined to lower obscuration ( N H ≤ 10 23 cm −2 ) and lower luminosity ( L 2−10 keV ≤ 10 42 erg s −1 ). Two galaxies, however, are clearly best fit as significantly obscured AGNs. At least half of this sample shows evidence of at least low-luminosity AGN activity, though none could radiatively drive out the remaining molecular gas reservoirs. Therefore, these AGNs are more likely along for the ride, having been fed gas by the same processes driving the transition.