A Search for H [CSC]i[/CSC] in E+A Galaxies

Abstract

We present the results of H I line and radio continuum observations of five nearby E+A galaxies. These galaxies have spectra that are dominated by a young stellar component but lack the emission lines characteristic of significant ongoing star formation. They are selected from a unique sample of 21 E+A's identified by Zabludoff et al. in their spectroscopic search (published in 1996) for E+A galaxies using the Las Campanas Redshift Survey, in which over 11,000 nearby galaxies were examined. The five E+A galaxies span a range of environments: three are in the field, and two are in clusters. Only one system was detected in H I emission, the field E+A galaxy EA 1, with a total flux of 0.30+/-0.02 Jy km s-1 and an H I mass of 3.5+/-0.2×109 h-2 Msolar. The H I morphology and kinematics of EA 1 suggest a galaxy-galaxy interaction, with a dynamical age of ~6×108 h-1 yr inferred from the H I tail lengths and velocities. This age estimate is consistent with the interpretation drawn from optical spectroscopy that starbursts in E+A galaxies began (and subsequently ended) within the last 109 yr. Our H I detection limits are such that if the other E+A's in our sample had the H I properties of EA 1, we would have detected (or marginally detected) them. We conclude that E+A galaxies have a range of H I properties. None of the galaxies were detected in radio continuum emission, with upper limits to the radio power of ~1021 h-2 W Hz-1. Our limits exclude the possibility that these E+A's are dust-enshrouded massive starburst galaxies, but they are insufficient to exclude modest star formation rates of less than a few h-2 Msolar yr-1.