Probing cold gas outflows in local star forming galaxies
Guido Roberts-Borsani
University College London
Amélie Saintonge
Star formation plays a crucial role in the evolution of galaxies. Since star formation relies on the presence of cold molecular gas, a thorough understanding of the evolution of the cold gas content is necessary: how does the gas enter a galaxy, how does it get transformed into stars, and how does it get ejected back out into the intergalactic medium?
In this project we investigate the presence (and role) of cold gas outflows in local, star-forming galaxies. We make use of COLD GASS CO(1-0) millimetre spectra and ALFALFA HI spectra to search for evidence of cold gas outflows in galaxies known to power ionised gas outflows as revealed by their SDSS optical spectra. Our selected sample consists of local (0.05 ≤ z ≤ 0.18) disk galaxies with young stellar populations and no AGN contributions. We stack the galaxy spectra to increase the S/N ratio to a level that allows us to accurately measure the broad component of absorption and emission lines – indicative of outflows - and determine whether cold gas outflows are present, and if so, how they relate to star formation rates and other global galaxy properties. Cold gas outflows could play an important role in the regulation of star formation and ultimately provide insight into the mechanisms that govern the evolution of galaxies.