More Like this

1. The First Combined H-alpha and Rest-UV Spectroscopic Probe of Galactic Outflows at High Redshift

   Kehoe, Emily; Shapley, Alice; Forster_Schreiber, Natascha; Pahl, Anthony; Topping, Michael; Reddy, Naveen; Genzel, Reinhard; Price, Sedona; Tacconi, Linda (June 2024, ApJ)

   We investigate the multi-phase structure of gas flows in galaxies. We study 80 galaxies during the epoch of peak star formation (1.4≤z≤2.7) using data from Keck/LRIS and VLT/KMOS. Our analysis provides a simultaneous probe of outflows using UV emission and absorption features and Hα emission. With this unprecedented data set, we examine the properties of gas flows estimated from LRIS and KMOS in relation to other galaxy properties, such as star formation rate (SFR), star formation rate surface density (ΣSFR), stellar mass (M∗), and main sequence offset (ΔMS). We find no strong correlations between outflow velocity measured from rest-UV lines centroids and galaxy properties. However, we find that galaxies with detected outflows show higher averages in SFR, ΣSFR, and ΔMS than those lacking outflow detections, indicating a connection between outflow and galaxy properties. Furthermore, we find a lower average outflow velocity than previously reported, suggesting greater absorption at the systemic redshift of the galaxy. Finally, we detect outflows in 49% of our LRIS sample and 30% in the KMOS sample, and find no significant correlation between outflow detection and inclination. These results may indicate that outflows are not collimated and that Hα outflows have a lower covering fraction than low-ionization interstellar absorption lines. Additionally, these tracers may be sensitive to different physical scales of outflow activity. A larger sample size with a wider dynamic range in galaxy properties is needed to further test this picture. 

   more » « less
2. 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. 

   more » « less
3. 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. 

   more » « less
4. DUVET: Spatially Resolved Observations of Star Formation Regulation via Galactic Outflows in a Starbursting Disk Galaxy

   https://doi.org/10.3847/1538-4357/aca1bd  

   Reichardt Chu, Bronwyn; Fisher, Deanne B.; Bolatto, Alberto D.; Chisholm, John; Fielding, Drummond; Berg, Danielle; Cameron, Alex J.; Glazebrook, Karl; Herrera-Camus, Rodrigo; Kacprzak, Glenn G.; et al (December 2022, The Astrophysical Journal)

   Abstract We compare 500 pc scale, resolved observations of ionized and molecular gas for the z ∼ 0.02 starbursting disk galaxy IRAS08339+6517, using measurements from KCWI and NOEMA. We explore the relationship of the star-formation-driven ionized gas outflows with colocated galaxy properties. We find a roughly linear relationship between the outflow mass flux ( Σ ̇ out ) and star formation rate surface density (Σ SFR ), Σ ̇ out ∝ Σ SFR 1.06 ± 0.10 , and a strong correlation between Σ ̇ out and the gas depletion time, such that Σ ̇ out ∝ t dep − 1.1 ± 0.06 . Moreover, we find these outflows are so-called breakout outflows, according to the relationship between the gas fraction and disk kinematics. Assuming that ionized outflow mass scales with total outflow mass, our observations suggest that the regions of highest Σ SFR in IRAS08 are removing more gas via the outflow than through the conversion of gas into stars. Our results are consistent with a picture in which the outflow limits the ability of a region of a disk to maintain short depletion times. Our results underline the need for resolved observations of outflows in more galaxies. 

   more » « less
5. The MOSDEF survey: properties of warm ionized outflows at z  = 1.4–3.8

   https://doi.org/10.1093/mnras/stae1428  

   Weldon, Andrew; Reddy, Naveen A; Coil, Alison L; Shapley, Alice E; Siana, Brian; Price, Sedona H; Kriek, Mariska; Mobasher, Bahram; Song, Zhiyuan; Wozniak, Michael A (June 2024, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT We use the large spectroscopic data set of the MOSFIRE Deep Evolution Field survey to investigate the kinematics and energetics of ionized gas outflows. Using a sample of 598 star-forming galaxies at redshift 1.4 < z < 3.8, we decompose [O iii] and $$\rm {H}\,\alpha$$ emission lines into narrow and broad components, finding significant detections of broad components in 10 per cent of the sample. The ionized outflow velocity from individual galaxies appears independent of galaxy properties, such as stellar mass, star formation rate (SFR), and SFR surface density (ΣSFR). Adopting a simple outflow model, we estimate the mass-, energy-, and momentum-loading factors of the ionized outflows, finding modest values with averages of 0.33, 0.04, and 0.22, respectively. The larger momentum- than energy-loading factors, for the adopted physical parameters, imply that these ionized outflows are primarily momentum driven. We further find a marginal correlation (2.5σ) between the mass-loading factor and stellar mass in agreement with predictions by simulations, scaling as ηm$$\propto M_{\star }^{-0.45}$$. This shallow scaling relation is consistent with these ionized outflows being driven by a combination of mechanical energy generated by supernovae explosions and radiation pressure acting on dusty material. In a majority of galaxies, the outflowing material does not appear to have sufficient velocity to escape the gravitational potential of their host, likely recycling back at later times. Together, these results suggest that the ionized outflows traced by nebular emission lines are negligible, with the bulk of mass and energy carried out in other gaseous phases. 

   more » « less