Seminar by Yang Sun, Arizona
Post-starburst galaxies are caught in a rapid transition between star-forming and quiescent galaxies, where the star formation ended in the last ~Gyr. While galactic feedback has long been recognized as an important contribution to galaxy evolution, and galactic winds are common in galaxies with starbursts or AGN, the role of such gas flows in galaxy evolution, especially in star formation quenching, remains uncertain. We examine how neutral galactic winds vary along a likely evolutionary sequence connecting starburst to post-starburst to quiescent galaxies for the first time. To detect the interstellar medium and measure its bulk flows, we examine the residual NaD absorption lines after the stellar contribution has been removed from each galaxy’s spectrum. We discover that outflows diminish along this sequence, i.e., as star formation ends. Even within our post-starburst sample, the fraction of galaxies with significant winds and the average wind velocities decrease with post-burst age after controlling for stellar mass. We find most of the neutral outflows detected in post-starburst galaxies are not able to escape from the galaxies, suggesting those winds should play some other role in suppressing star formation than cleaning up the cold gas. For the post-starbursts, We also find evidence for an AGN contribution, especially to the fastest outflows. However, for the starbursts, the outflow velocity has the inclination dependency, suggesting those winds are driven by star formation, not AGN.
Host: Ann Zabludoff