The HI content of elliptical and lenticular galaxies with recent star formation

Abstract

As a first step toward constraining the efficiency of the star formation episodes that lead to elliptical (E) and lenticular (S0) K+A galaxies, a survey for HI within a sample of E and S0 K+A galaxies and their likely progenitors (i.e., actively star forming E and S0 galaxies) has been conducted with the NRAO Green Bank Telescope (GBT). The sample was taken from a larger parent sample drawn from the Sloan Digital Sky Survey (SDSS). Here, the GBT data and initial results are discussed. Over half (19 out of 30) of all observed galaxies have detectable 21-cm emission. It was found that both the K+A and star forming early-type (SFE) galaxies were on average more gas poor than disk galaxies at the same luminosity while being more gas rich than more typical E and S0 galaxies with detected 21-cm emission. The gas richness of K+A galaxies appears to be similar to that of SFE galaxies. The star formation rates and estimated star formation time scales of the SFE galaxies imply that they are capable of only marginally changing their atomic hydrogen content. Follow-up observations are required to explore these same issues in terms of molecular gas, which is more likely to actively participate in the star formation process. Kinematic data for the HI gas, the warm ionised gas, and the stars within the galaxies combined with the SDSS $g$ and $i$ band surface brightness profiles imply that the atomic hydrogen is most likely spatially coincident with the star forming regions within ~1 kpc of the galaxies' centres.