Stellar population gradients in the cores of nearby field E+A galaxies
  We have selected a sample of local E+A galaxies from the Sloan Digital Sky
Survey (SDSS) Data Release 7 for follow up integral field spectroscopy with the
Wide Field Spectrograph (WiFeS) on the ANU 2.3-m telescope. The sample was
selected using the Halpha line in place of the [OII]3727 line as the indicator
of on-going star formation (or lack thereof). This allowed us to select a lower
redshift sample of galaxies than available in the literature since the
[OII]3727 falls off the blue end of the wavelength coverage in the SDSS for the
very lowest redshift objects. This low redshift selection means that the
galaxies have a large angular to physical scale which allows us to resolve the
central ~1kpc region of the galaxies; the region where stellar population
gradients are expected. Such observations have been difficult to make using
other higher redshift samples because even at redshifts z~0.1 the angular to
physical scale is similar to the resolution provided by ground based seeing.
Our integral field spectroscopy has enabled us to make the first robust
detections of Balmer line gradients in the centres of E+A galaxies. Six out of
our sample of seven, and all the galaxies with regular morphologies, are
observed to have compact and centrally-concentrated Balmer line absorption.
This is evidence for compact young cores and stellar population gradients which
are predicted from models of mergers and tidal interactions which funnel gas
into the galaxy core. Given the generally isolated nature of our sample this
argues for the galaxies being seen in the late stage of a merger where the
progenitors have already coalesced.
