Stellar population gradients and spatially resolved kinematics in luminous post-starburst galaxies

We have used deep integral field spectroscopy obtained with the Gemini Multi-Object Spectrograph (GMOS) instrument on Gemini-North to determine the spatial distribution of the post-starburst stellar population in four luminous (∼L*) E+A galaxies at z < 0.04. We find that all four galaxies have centrally concentrated gradients in the young stellar population contained within the central ∼1 kpc. This is in agreement with the Balmer line gradients found in local low-luminosity E+A galaxies. The results from higher redshift (z ∼ 0.1) samples of luminous E+A galaxies have been varied, but in general have found the post-starburst signature to be extended or a galaxy-wide phenomenon or have otherwise failed to detect gradients in the stellar populations. The ubiquity of the detection of a centrally concentrated young stellar population in local samples, and the presence of significant radial gradients in the stellar populations when the E+A galaxy core is well resolved raises the possibility that spatial resolution issues may be important in interpreting the higher redshift results. The two early-type E+A galaxies in our sample that can be robustly kinematically classified, using the λR parameter, are fast rotators. Combined with previous measurements, this brings the total number of E+A galaxies with measurements of λR to 26, with only four being classified as slow rotators. This fraction is similar to the fraction of the early-type population as a whole and argues against the need for major mergers in the production of E+A galaxies, since major mergers should result in an increased fraction of slow rotators.