Integral field spectroscopy of two H I-rich E+A galaxies

Abstract

Approximately half of the nearby E+A galaxies followed up with 21-cm observations have detectable HI emission. The optical spectra of these galaxies show strong post-starburst stellar populations but no optical emission lines implying star formation is not ongoing despite the presence of significant gas reservoirs. We have obtained integral field spectroscopic followup observations of the two brightest, and nearest, of the six E+A galaxies with HI 21-cm emission in the recent sample of Zwaan et al. In the central regions of both galaxies, the observations are consistent with a post-starburst population with little emission. However, outside the central regions both galaxies have strong optical emission lines, with a clumpy or knot-like distribution, indicating ongoing star formation.We conclude that in these two cases, the presence of optical spectra lacking evidence for star formation while a large gas mass is present can be explained by an aperture effect in selecting the nearby E+A galaxies using single-fibre spectroscopy that probes only the galaxy core. © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.