A Gemini/GMOS-IFU Spectroscopy of E+A Galaxies in the Mid-infrared Green Valley: On the Spatial Distribution of Young Stellar Population

We present the two-dimensional distribution of stellar populations in five E+A galaxies from GMOS-N/IFU spectroscopy (GN-2015B-Q-15). Numerical simulations demonstrated that E+A galaxies formed by major mergers contain young stellar populations (e.g. A-type stars) that are centrally-concentrated within scales of 1 kpc. However, several IFU studies reported that A-type stars are widely distributed on ${\gg}$ 1kpc scales. In contrast, Pracy et al. (2013) found a central concentration of A-stars and strong negative Balmer absorption line gradients within 1 kpc scales for local (z < 0.03) E+A galaxies. They claimed that previous studies failed to detect the central concentration because the E+A galaxy samples in previous studies are too far (z ~ 0.1) to resolve the central kpc scales. To verify Pracy et al.'s argument and the expectation from simulations, we selected five E+A galaxies at 0.03 < z < 0.05. Furthermore, we selected the targets in the mid-infrared green valley (Lee et al. 2015). Thanks to good seeing (${\sim}0.4^{{\prime}{\prime}}{\simeq}0.33kpc$) of our observation, we are able to resolve the central 1 kpc region of our targets. We found that all five galaxies have negative Balmer line gradients, but that three galaxies have flatter gradients than those reported in Pracy et al. We discuss the results in relation with galaxy merger history.