Program: GN-2017B-Q-17

Post-starburst, or "E+A" galaxies are in a transition phase from star-forming galaxies into quiescent galaxies. Their spectra reveal that the galaxies must have undergone a phase of vigorous starburst which was abruptly quenched within the last ~1 Gyr. Moreover, numerical simulations predict that these starbursts cause the E+A signature to be localized within the host's centers (<1 kpc). Indeed, the findings of Pracy et al. (2013) corroborate this prediction. However, the results from our previous GMOS IFU observations (GN-2015B-Q-15) and several other past studies show that this is not always the case. We found that all five of the galaxies we examined show negative Hdelta absorption line gradients. This result suggests that A stars are not just confined to the central regions of E+A galaxies (Lee et al., in prep), and more importantly, gives rise to the question of why some E+A galaxies have a central concentration of A stars while others do not. Furthermore, we found a negative correlation between the slope of these Hdelta gradients and the fractions of stellar mass produced during starburst. This correlation can be understood if E+A galaxies with stronger starbursts have more centrally-concentrated bursts, or can arise from just the three most extreme points, which have large errors, at >0.8 burst mass fraction. In order to verify this tentative correlation, we propose deep observations with the GMOS IFU of five nearby (z<0.04) E+A galaxies with full range of burst mass fractions spanning 0 to 1.