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Abstract We investigate the multiphase 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 the Keck/Low-Resolution Imaging Spectrometer (LRIS) and the Very Large Telescope/K-Band Multi-Object Spectrograph (KMOS). Our analysis provides a simultaneous probe of outflows using UV emission and absorption features and Hαemission. 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), SFR surface density (Σ_SFR), stellar mass (M_*), and main-sequence offset (ΔMS). We find no strong correlations between outflow velocity measured from rest-UV line centroids and galaxy properties. However, we find that galaxies with detected outflows show higher averages in SFR, Σ_SFR, 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 Hαoutflows 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. 

Abstract JWST observations have recently begun delivering the first samples of Lyαvelocity profile measurements atz> 6, opening a new window into the reionization process. Interpretation ofz≳ 6 line profiles is currently stunted by limitations in our knowledge of the intrinsic Lyαprofile (before encountering the intergalactic medium (IGM)) of the galaxies that are common atz≳ 6. To overcome this shortcoming, we have obtained resolved (R∼ 3900) Lyαspectroscopy of 42 galaxies atz= 2.1–3.4 with similar properties as are seen atz> 6. We quantify a variety of Lyαprofile statistics as a function of [Oiii]+Hβequivalent width (EW). Our spectra reveal a new population ofz≃ 2–3 galaxies with large [Oiii]+HβEWs (>1200 Å) and a large fraction of Lyαflux emerging near the systemic redshift (peak velocity ≃0 km s⁻¹). These spectra indicate that low-density neutral hydrogen channels are able to form in a subset of low-mass galaxies (≲1 × 10⁸M_⊙) that experience a burst of star formation (sSFR > 100 Gyr⁻¹). Other extreme [Oiii] emitters show weaker Lyαthat is shifted to higher velocities (≃240 km s⁻¹) with little emission near the line center. We investigate the impact the IGM is likely to have on these intrinsic line profiles in the reionization era, finding that the centrally peaked Lyαemitters should be strongly attenuated atz≳ 5. We show that these line profiles are particularly sensitive to the impact of resonant scattering from infalling IGM and can be strongly attenuated even when the IGM is highly ionized atz≃ 5. We compare these expectations against a new database ofz≳ 6.5 galaxies with robust velocity profiles measured with JWST/NIRSpec. 

ABSTRACT We report on the discovery of cool gas inflows towards three star-forming galaxies at <z> ∼ 2.30. Analysis of Keck Low-Resolution Imaging Spectrometer spectroscopy reveals redshifted low-ionization interstellar (LIS) metal absorption lines with centroid velocities of 60–130 km s−1. These inflows represent some of the most robust detections of inflowing gas into isolated, star-forming galaxies at high redshift. Our analysis suggests that the inflows are due to recycling metal-enriched gas from previous ejections. Comparisons between the galaxies with inflows and a larger parent sample of 131 objects indicate that galaxies with detected inflows may have higher specific star formation rates (sSFRs) and star-formation-rate surface densities (ΣSFR). However, when additional galaxies without robustly detected inflows based on centroid velocity but whose LIS absorption line profiles indicate large red-wing velocities are considered, galaxies with inflows do not show unique properties relative to those lacking inflows. Additionally, we calculate the covering fraction of cool inflowing gas as a function of red-wing inflow velocity, finding an enhancement in high-sSFR binned galaxies, likely due to an increase in the amount of recycling gas. Together, these results suggest that the low detection rate of galaxies with cool inflows is primarily related to the viewing angle rather than the physical properties of the galaxies.