Program: GN-2017A-Q-1

Post-starburst, or "E+A" galaxies, are products of galaxy mergers and in rapid transition from star-forming spirals to gas-poor "red and dead" early-type galaxies. Yet we have discovered that over half of post-starburst galaxies still have large molecular gas reservoirs, comparable even to those of star-forming galaxies. Our ALMA observations have now constrained the molecular gas to be within only 1.5 kpc from the center in the post-starburst galaxies observed thus far. Therefore, the end of the starburst is not due to the complete consumption, expulsion, or starvation of the gas, as previously suggested. Some other mechanism is preventing the cold gas from forming stars now. One possibility is the feedback from a central, supermassive black hole, indeed, most post-starburst galaxies have LINER emission. Another is that stellar outflows, ionization by post-AGB stars, or merger-induced shock might lower the star formation efficiency in these systems. To test these possibilities and constrain what stops galactic star formation, we propose to obtain high-resolution GMOS IFU observations of the stellar continuum, the Halpha, [NII], [SII] emission lines, and Na D absorption lines from three post-starburst galaxies with very young post-burst ages. Combined with the approved ALMA observations, the proposed GMOS observations will map the star formation efficiency within post-starburst galaxies for the first time, and test how they are correlated with potential causes for the suppressed star formation.