Evolution of gas flows along the starburst to post-starburst to quiescent galaxy sequence

We measure velocity offsets in the NaI lambda lambda 5890, 5896 (NaD) interstellar medium absorption lines to track how neutral galactic winds change as their host galaxies evolve. Our sample of similar to 80 000 SDSS spectra at 0.010 < z < 0.325 includes starburst, post-starburst, and quiescent galaxies, forming an evolutionary sequence of declining star formation rate (SFR). We detect bulk flows across this sequence, mostly at higher host stellar masses (log(M-*/M-circle dot)) > 10). Along this sequence, the fraction of outflows decreases (76 +/- 2 per cent to 65 +/- 4 per cent to a 3 sigma upper limit of 34 per cent), and the mean velocity offset changes from outflowing to inflowing (-84.6 +/- 5.9 to -71.6 +/- 11.4 to 76.6 +/- 2.3kms-1). Even within the post-starburst sample, wind speed decreases with time elapsed since the starburst ended. These results reveal that outflows diminish as galaxies age. For post-starbursts, there is evidence for an AGN contribution, especially to the speediest outflows: (1) SFR declines faster in time than outflow velocity, a decoupling arguing against massive stellar feedback; (2) of the few outflows strong enough to escape the interstellar medium (9/105), three of the four hosts with measured emission lines are Seyfert galaxies. For discy starburst galaxies, however, the trends suggest flows out of the stellar disc plane (with outflow 1/2-opening angle > 45 degrees) instead of from the nucleus: the wind velocity decreases as the disc becomes more edge-on, and the outflow fraction, constant at similar to 90 per cent for disc inclinations i < 45 degrees, steadily decreases from similar to 90 per cent to 20 per cent for i > 45 degrees.