Searching for local counterparts of high-redshift post-starburst galaxies in integral field unit spectroscopic surveys of nearby galaxies

Abstract

Searching in the MaNGA IFU survey, I identify 9 galaxies that have strong Balmer absorption lines and weak nebular emission lines measured from the spectra integrated over the entire IFUs. The spectral features measured from the bulk of the stellar light make these galaxies local analogs of high-redshift spectroscopically-selected post-starburst galaxies, thus, proxies to understand the mechanisms producing post-starburst galaxies at high-redshifts. I present the distributions of absorption-line indices and emission-line strengths, as well as stellar kinematics of these local post-starburst galaxies. Almost all local post-starburst galaxies have central compact emission-line regions at the central < 1 kpc, mostly powered by weak star-formation activities. The age-sensitive absorption line indices EW(Hδ) and D n 4000 indicate that the stellar populations at the outskirts are older. Toy stellar population synthesis models suggest that the entire galaxies are experiencing a rapid decline of star formation with residual star-formation activities at the centers. These features demand that most poststarburst galaxies are the aftermath of highly dissipative processes that drive gas into centers, invoke centrally-concentrated star formation, then quench the galaxies. Meanwhiles, when measurable, poststarburst galaxies have the directions of maximum stellar velocity gradients align with photometric major axes, which suggest against major mergers being the principal driving mechanism, while gas-rich minor mergers are plausible. While directly obtaining the same quality of spatially-resolved spectra of high-redshift post-starburst galaxies is very difficult, finding proper local counterparts provides an alternative to understand quenching processes in the distant Universe.