Outflows in star-forming galaxies: Stacking analyses of resolved winds and the relation to their hosts' properties

Abstract

Outflows form an integral component in regulating the gas cycling in and out of galaxies, although their impact on the galaxy hosts is still poorly understood. Here we present an analysis of 405 high mass (log Mz.ast;/M⊙≥ 10), star-forming galaxies (excluding AGN) with low inclinations at z ~ 0, using stacking techniques of the NaD λλ5889, 5895Å neutral gas tracer in IFU observations from the MaNGA DR15 survey. We detect outflows in the central regions of 78/405 galaxies and determine their extent and power through the construction of stacked annuli.We find outflows are most powerful in central regions and extend out to ~1Re, with declining mass outflow rates and loading factors as a function of radius. The stacking of spaxels over key galaxy quantities reveals outflow detections in regions of high ΣSFR (≥0.01M⊙ yr-2 kpc-2) and ΣMz.ast; (≥107M⊙ kpc-2) along the resolved main sequence. Clear correlations with ΣSFR suggest it is the main regulator of outflows, with a critical threshold of ~0.01M⊙ yr-1 kpc-2 needed to escape the weight of the disc and launch them. Furthermore, measurements of the Hδ and Dn4000 indices reveal virtually identical star formation histories between galaxies with outflows and those without. Finally, through stacking of HI 21 cm observations for a subset of our sample, we find outflow galaxies show reduced HI gas fractions at central velocities compared to their non-detection control counterparts, suggestive of some removal of HI gas, likely in the central regions of the galaxies, but not enough to completely quench the host.