Interacting E+A system SDSS J161330.18+510335.5. I. Spatially extended poststarburst signatures and age gradient

An E+A galaxy and its neighbor were viewed with a long-slit spectrograph (FOCAS) mounted on the Subaru telescope. The galaxy is thought to be experiencing a dynamical interaction with its neighbor, and we have confirmed that the neighbor galaxy is at the same redshift. The neighbor galaxy shows no signs of current star formation or poststarburst activity. We investigated the spatial extent of the poststarburst signatures using long-slit spectroscopy of the E+A galaxy. The signatures extend over more than 5 kpc from the core to the tidal plume, which suggests that the starburst was a galaxy-wide phenomenon. We found a positive gradient in the age of young stars from the center to the outer regions of the plume.