A HIGH-RESOLUTION STUDY OF THE ATOMIC HYDROGEN IN CO-RICH EARLY-TYPE GALAXIES

Abstract

We present an analysis of new and archival Very Large Array H i observations of a sample of 11 early-type galaxies rich in CO, with detailed comparisons of CO and H i distributions and kinematics. The early-type sample consists of both lenticular and elliptical galaxies in a variety of environments. A range of morphologies and environments were selected in order to give a broader understanding of the origins, distribution, and fate of the cold gas in early-type galaxies. Six of the eleven galaxies in the sample are detected in both H i and CO. The H2 to H i mass ratios for this sample range from 0.2 to 120. The H i morphologies of the sample are consistent with that of recent H i surveys of early-type galaxies, which also find a mix of H i morphologies and masses, low H i peak surface densities, and a lack of H i in early-type galaxies that reside in high-density environments. The HI-detected galaxies have a wide range of H i masses (1.4 × 106 to 1.1 × 1010 M☉). There does not appear to be any correlation between the H i mass and morphology (E versus S0). When H i is detected, it is centrally peaked—there are no central kiloparsec-scale central H i depressions like those observed for early-type spiral galaxies at similar spatial resolutions and scales. A kinematic comparison between the H i and CO indicates that both cold gas components share the same origin. The primary goal of this and a series of future papers is to better understand the relationship between the atomic and molecular gas in early-type galaxies, and to compare the observed relationships with those of spiral galaxies where this relationship has been studied in depth.