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Abstract While stellar processes are believed to be the main source of feedback in dwarf galaxies, the accumulating discoveries of active galactic nuclei (AGN) in dwarf galaxies over recent years arouse the interest to also consider AGN feedback in them. Fast, AGN-driven outflows, a major mechanism of AGN feedback, have indeed been discovered in dwarf galaxies and may be powerful enough to provide feedback to their dwarf hosts. In this paper, we search for outflows traced by the blueshifted ultraviolet absorption features in three dwarf galaxies with AGN from the sample examined in our previous ground-based study. We confirm outflows traced by blueshifted absorption features in two objects and tentatively detect an outflow in the third object. In one object where the outflow is clearly detected in multiple species, photoionization modeling suggests that this outflow is located ∼0.5 kpc from the AGN, implying a galactic-scale impact. This outflow is much faster and possesses a higher kinetic energy outflow rate than starburst-driven outflows in sources with similar star formation rates, and is likely energetic enough to provide negative feedback to its host galaxy as predicted by simulations. Much broader (∼4000 km s⁻¹) absorption features are also discovered in this object, which may have the same origin as that of broad absorption lines in quasars. Additionally, strong Heiiλ1640 emission is detected in both objects where the transition falls in the wavelength coverage and is consistent with an AGN origin. In one of these two objects, a blueshifted Heiiλ1640 emission line is clearly detected, likely tracing a highly ionized AGN wind. 

Abstract This study addresses how the incidence rate of strong Oviabsorbers in a galaxy’s circumgalactic medium (CGM) depends on galaxy mass and, independently, on the amount of star formation in the galaxy. We use Hubble Space Telescope/Cosmic Origins Spectrograph absorption spectroscopy of quasars to measure Oviabsorption within 400 projected kpc and 300 km s⁻¹of 52 galaxies withM_*∼ 3 × 10¹⁰M_⊙. The galaxies have redshifts 0.12 <z< 0.6, stellar masses 10^10.1M_⊙<M_*< 10^10.9M_⊙, and spectroscopic classifications as star-forming or passive. We compare the incidence rates of high column density Oviabsorption (N_OVI≥ 10^14.3cm⁻²) near star-forming and passive galaxies in two narrow ranges of stellar mass and, separately, in a matched range of halo mass. In all three mass ranges, the Ovicovering fraction within 150 kpc is higher around star-forming galaxies than around passive galaxies with greater than 3σ-equivalent statistical significance. On average, the CGM of star-forming galaxies withM_*∼ 3 × 10¹⁰M_⊙contains more Ovithan the CGM of passive galaxies with the same mass. This difference is evidence for a CGM transformation that happens together with galaxy quenching and is not driven primarily by halo mass. 

Abstract We combine data sets from the CGM²and CASBaH surveys to model a transition point,R_cross, between circumgalactic and intergalactic media (CGM and IGM, respectively). In total, our data consist of 7244 galaxies atz< 0.5 with precisely measured spectroscopic redshifts, all having impact parameters of 0.01–20 comoving Mpc from 28 QSO sightlines with high-resolution UV spectra that cover HiLyα. Our best-fitting model is a two-component model that combines a 3D absorber–galaxy cross-correlation function with a simple Gaussian profile at inner radii to represent the CGM. By design, this model gives rise to a determination ofR_crossas a function of galaxy stellar mass, which can be interpreted as the boundary between the CGM and IGM. For galaxies with 10⁸≤M_⋆/M_⊙≤ 10^10.5, we find thatR_cross(M_⋆) ≈ 2.0 ± 0.6R_vir. Additionally, we find excellent agreement betweenR_cross(M_⋆) and the theoretically determined splashback radius for galaxies in this mass range. Overall, our results favor models of galaxy evolution atz< 0.5 that distributeT≈ 10⁴K gas to distances beyond the virial radius. 

ABSTRACT Quasar absorption systems encode a wealth of information about the abundances, ionization structure, and physical conditions in intergalactic and circumgalactic media. Simple (often single-phase) photoionization models are frequently used to decode such data. Using five discrete absorbers from the COS Absorption Survey of Baryon Harbors (CASBaH) that exhibit a wide range of detected ions (e.g. Mg ii, S ii – S vi, O ii – O vi, Ne viii), we show several examples where single-phase ionization models cannot reproduce the full set of measured column densities. To explore models that can self-consistently explain the measurements and kinematic alignment of disparate ions, we develop a Bayesian multiphase ionization modelling framework that characterizes discrete phases by their unique physical conditions and also investigates variations in the shape of the UV flux field, metallicity, and relative abundances. Our models require at least two (but favour three) distinct ionization phases ranging from T ≈ 104 K photoionized gas to warm-hot phases at T ≲ 105.8 K. For some ions, an apparently single absorption ‘component' includes contributions from more than one phase, and up to 30 per cent of the H i is not from the lowest ionization phase. If we assume that all of the phases are photoionized, we cannot find solutions in thermal pressure equilibrium. By introducing hotter, collisionally ionized phases, however, we can achieve balanced pressures. The best models indicate moderate metallicities, often with subsolar N/α, and, in two cases, ionizing flux fields that are softer and brighter than the fiducial Haardt & Madau UV background model. 

Abstract We combine 126 new galaxy-Oviabsorber pairs from the CGM²survey with 123 pairs drawn from the literature to examine the simultaneous dependence of the column density of Oviabsorbers (N_OVI) on galaxy stellar mass, star-formation rate, and impact parameter. The combined sample consists of 249 galaxy-Oviabsorber pairs coveringz= 0–0.6, with host galaxy stellar massesM_*= 10^7.8–10^11.2M_⊙and galaxy-absorber impact parametersR_⊥= 0–400 proper kiloparsecs. In this work, we focus on the variation ofN_OVIwith galaxy mass and impact parameter among the star-forming galaxies in the sample. We find that the averageN_OVIwithin one virial radius of a star-forming galaxy is greatest for star-forming galaxies withM_*= 10^9.2–10¹⁰M_⊙. Star-forming galaxies withM_*between 10⁸and 10^11.2M_⊙can explain most Ovisystems with column densities greater than 10^13.5cm⁻². Sixty percent of the Ovimass associated with a star-forming galaxy is found within one virial radius, and 35% is found between one and two virial radii. In general, we find that some departure from hydrostatic equilibrium in the CGM is necessary to reproduce the observed Oviamount, galaxy mass dependence, and extent. Our measurements serve as a test set for CGM models over a broad range of host galaxy masses.