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1. The Outflowing [O ii] Nebulae of Compact Starburst Galaxies at z ∼ 0.5

   https://doi.org/10.3847/1538-4357/ad7b0c  

   Perrotta, Serena; Coil, Alison L; Rupke, David_S N; Ning, Wenmeng; Duong, Brendan; Diamond-Stanic, Aleksandar M; Fielding, Drummond B; Geach, James E; Hickox, Ryan C; Moustakas, John; et al (November 2024, The Astrophysical Journal)

   Abstract High-velocity outflows are ubiquitous in compact, massive (M_*∼ 10¹¹M_⊙),z∼ 0.5 galaxies with extreme star formation surface densities (Σ_SFR∼ 2000M_⊙yr⁻¹kpc⁻²). We have previously detected and characterized these outflows using Mgiiabsorption lines. To probe their full extent, we present Keck/KCWI integral field spectroscopy of the [Oii] and Mgiiemission nebulae surrounding all of the 12 galaxies in this study. We find that [Oii] is more effective than Mgiiin tracing low surface brightness, extended emission in these galaxies. The [Oii] nebulae are spatially extended beyond the stars, with radial extentR₉₀between 10 and 40 kpc. The nebulae exhibit nongravitational motions, indicating galactic outflows with maximum blueshifted velocities ranging from −335 to −1920 km s⁻¹. The outflow kinematics correlate with the bursty star formation histories of these galaxies. Galaxies with the most recent bursts of star formation (within the last <3 Myr) exhibit the highest central velocity dispersions (σ≳ 400 km s⁻¹), while the oldest bursts have the lowest-velocity outflows. Many galaxies exhibit both high-velocity cores and more extended, slower-moving gas indicative of multiple outflow episodes. The slower, larger outflows occurred earlier and have decelerated as they propagate into the circumgalactic medium and mix on timescales ≳50 Myr. 

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2. Ionized Gas Outflows in the Galaxy and Mass Assembly (GAMA) Survey: Signatures of AGN Feedback in Low-mass Galaxies

   https://doi.org/10.3847/1538-4357/ad9a57  

   Salehirad, Sheyda; Reines, Amy E; Molina, Mallory (January 2025, The Astrophysical Journal)

   Abstract We present a sample of 398 galaxies with ionized gas outflow signatures in their spectra from the Galaxy and Mass Assembly Survey Data Release 4, including 45 low-mass galaxies with stellar massesM_* < 10¹⁰M_⊙. We assemble our sample by systematically searching for the presence of a second velocity component in the [O iii]λλ4959, 5007 doublet emission line in 39,612 galaxies with redshiftsz < 0.3. The host galaxies are classified using the Baldwin–Phillips–Terlevich diagram, with ~89% identified as active galactic nuclei (AGNs) and composites and 11% as star-forming (SF) galaxies. The outflows are typically faster in AGNs with a median velocity of 936 km s⁻¹compared to 655 km s⁻¹in the SF objects. Of particular interest are the 45 galaxies in the low-mass range, of which a third are classified as AGNs/composites. The outflows from the low-mass AGNs are also faster and more blueshifted compared to those in the low-mass SF galaxies. This indicates that black hole outflows can affect host galaxies in the low-mass range and that AGN feedback in galaxies withM_* < 10¹⁰M_⊙should be considered in galaxy evolution models. 

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3. Kinematics, Structure, and Mass Outflow Rates of Extreme Starburst Galactic Outflows

   https://doi.org/10.3847/1538-4357/acc660  

   Perrotta, Serena; Coil, Alison L.; Rupke, David S.; Tremonti, Christy A.; Davis, Julie D.; Diamond-Stanic, Aleksandar M.; Geach, James E.; Hickox, Ryan C.; Moustakas, John; Rudnick, Gregory H.; et al (May 2023, The Astrophysical Journal)

   Abstract We present results on the properties of extreme gas outflows in massive (M_*∼ 10¹¹M_⊙), compact, starburst (star formation rate, SFR∼ 200M_⊙yr⁻¹) galaxies atz= 0.4–0.7 with very high star formation surface densities (Σ_SFR∼ 2000M_⊙yr⁻¹kpc⁻²). Using optical Keck/HIRES spectroscopy of 14 HizEA starburst galaxies, we identify outflows with maximum velocities of 820–2860 km s⁻¹. High-resolution spectroscopy allows us to measure precise column densities and covering fractions as a function of outflow velocity and characterize the kinematics and structure of the cool gas outflow phase (T∼ 10⁴K). We find substantial variation in the absorption profiles, which likely reflects the complex morphology of inhomogeneously distributed, clumpy gas and the intricacy of the turbulent mixing layers between the cold and hot outflow phases. There is not a straightforward correlation between the bursts in the galaxies’ star formation histories and their wind absorption line profiles, as might naively be expected for starburst-driven winds. The lack of strong Mgiiabsorption at the systemic velocity is likely an orientation effect, where the observations are down the axis of a blowout. We infer high mass outflow rates of ∼50–2200M_⊙yr⁻¹, assuming a fiducial outflow size of 5 kpc, and mass loading factors ofη∼ 5 for most of the sample. While these values have high uncertainties, they suggest that starburst galaxies are capable of ejecting very large amounts of cool gas that will substantially impact their future evolution. 

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4. Shocked POststarburst Galaxy Survey. IV. Outflows in Shocked Poststarburst Galaxies Are Not Responsible for Quenching

   https://doi.org/10.3847/1538-4357/ad900f  

   Fodor, Antoniu; Tomko, Taylor; Braun, Mary; Medling, Anne M; Johnson, Thomas M; Thompson, Alexander; Johnston, Victor D; Newhouse, Matthew; Luo, Yuanze; French, K Decker; et al (January 2025, The Astrophysical Journal)

   Abstract Shocked POstarburst Galaxies (SPOGs) exhibit both emission lines suggestive of shock-heated gas and poststarburst-like stellar absorption, resulting in a unique subset for galaxy evolution studies. We have observed 77 galaxies that fulfilled the SPOG criteria selection using the DeVeny Spectrograph on the Lowell Discovery Telescope. Our long-slit minor axis spectra detect Hαand [OIII] in some SPOGs out to 6 kpc above the galactic plane. We find extraplanar ionized gas in 31 targets of our sample overall. Using their internal and external kinematics, we argue that 22 galaxies host outflows with ionized gas masses ranging from 10²M_⊙to 10⁵M_⊙. The rest are likely extended diffuse ionized gas. A positive correlation exists between active galactic nuclei (AGN) luminosity and the extraplanar gas extent, velocity dispersion, and mass—suggesting that the AGN may indeed drive the outflows detected in AGN hosts. The low masses of the extraplanar gas suggest that these outflows are not depleting each galaxy’s gas reserves. The outflows, therefore, are not likely a significant quenching mechanism in these SPOGs. 

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5. Extreme FeLoBAL outflow in the VLT/UVES spectrum of quasar SDSS J1321−0041

   https://doi.org/10.1051/0004-6361/202348215  

   Byun, Doyee; Arav, Nahum; Sharma, Mayank; Dehghanian, Maryam; Walker, Gwen (April 2024, Astronomy & Astrophysics)

   Context.Quasar outflows are often analyzed to determine their ability to contribute to active galactic nucleus (AGN) feedback. We identified a broad absorption line (BAL) outflow in the VLT/UVES spectrum of the quasar SDSS J1321−0041. The outflow shows troughs from Fe II, and is thus categorized as an FeLoBAL. This outfow is unusual among the population of FeLoBAL outflows, as it displays C IIand Si IIBALs. Aims.Outflow systems require a kinetic luminosity above ∼0.5% of the quasar’s luminosity to contribute to AGN feedback. For this reason, we analyzed the spectrum of J1321−0041 to determine the outflow’s kinetic luminosity, as well as the quasar’s bolometric luminosity. Methods.We measured the ionic column densities from the absorption troughs in the spectrum and determined the hydrogen column density and ionization parameter using those column densities as our constraints. We also determined the electron number density,n_e, based on the ratios between the excited-state and resonance-state column densities of Fe IIand Si II. This allowed us to find the distance of the outflow from its central source, as well as its kinetic luminosity. Results.We determined the kinetic luminosity of the outflow to be 8.4_−5.4^+13.7 × 10⁴⁵ erg s⁻¹and the quasar’s bolometric luminosity to be 1.72 ± 0.13 × 10⁴⁷ erg s⁻¹, resulting in a ratio ofĖ_k/L_Bol = 4.8_−3.1^+8.0%. We conclude that this outflow has a sufficiently high kinetic luminosity to contribute to AGN feedback. 

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