Demographics and Physical Properties of Gas Out/Inflows at 0.4 < z < 1.4

TL;DR

This study analyzes gas inflows and outflows in over 200 galaxies between redshifts 0.4 and 1.4, revealing collimated outflows, low infall detection, and correlations with galaxy properties, advancing understanding of galaxy evolution.

Contribution

It provides the first comprehensive characterization of gas flows in galaxies at these redshifts, highlighting the collimation of outflows and the properties of infalling streams.

Findings

Net blueshift of FeII absorption in star-forming galaxies

Outflow fraction declines at low specific star formation rates

Low detection rate of infalling gas suggests aligned streams

Abstract

We present Keck/LRIS spectra of over 200 galaxies with well-determined redshifts between 0.4 and 1.4. We combine new measurements of near-ultraviolet, low-ionization absorption lines with previously measured masses, luminosities, colors, and star formation rates to describe the demographics and properties of galactic flows. Among star-forming galaxies with blue colors, we find a net blueshift of the FeII absorption greater than 200 km/s (100 km/s) towards 2.5% (20%) of the galaxies. The fraction of blueshifted spectra does not vary significantly with stellar mass, color, or luminosity but does decline at specific star formation rates less than roughly 0.8 Gyr^{-1}. The insensitivity of the blueshifted fraction to galaxy properties requires collimated outflows at these redshifts, while the decline in outflow fraction with increasing blueshift might reflect the angular dependence of the outflow velocity. The low detection rate of infalling gas, 3 to 6% of the spectra, suggests an origin in (enriched) streams favorably aligned with our sightline. We find 4 of these 9 infalling streams have projected velocities commensurate with the kinematics of an extended disk or satellite galaxy. The strength of the MgII absorption increases with stellar mass, B-band luminosity, and U-B color, trends arising from a combination of more interstellar absorption at the systemic velocity and less emission filling in more massive galaxies. Our results provides a new quantitative understanding of gas flows between galaxies and the circumgalactic medium over a critical period in galaxy evolution.