2019MNRAS.482.4111R

We perform a stacking analysis of the neutral Na D λλ5889, 5895 Å ISM doublet using the SDSS DR7 spectroscopic data set to probe the prevalence and characteristics of cold (T <= 10⁴ K) galactic-scale gas flows in local (0.025 <= z <= 0.1) inactive and AGN-host galaxies across the SFR-M_* plane. We find low-velocity outflows to be prevalent in regions of high SFRs and stellar masses (10 <= log M_*/M_☉ <= 11.5), however we do not find any detections in the low-mass (log M_*/M_☉ <= 10) regime. We also find tentative detections of inflowing gas in high-mass galaxies across the star-forming population. We derive mass outflow rates in the range of 0.14-1.74 M_☉ yr^–1 and upper limits on inflow rates <1 M_☉ yr^–1, allowing us to place constraints on the mass-loading factor (η = {dot}M_out/SFR) for use in simulations of the local Universe. We discuss the fate of the outflows by comparing the force provided by the starburst to the critical force needed to push the outflow outward, and find the vast majority of the outflows unlikely to escape the host system. Finally, as outflow detection rates and central velocities do not vary strongly with the presence of a (weak) active supermassive black hole, we determine that star formation appears to be the primary driver of outflows at z ∼ 0.