A High Resolution Study of the Atomic Hydrogen in CO-Rich Early-Type Galaxies

Abstract

We present an analysis of new and archival VLA HI observations of a sample of eleven early-type galaxies rich in CO, with detailed comparisons of CO and HI 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 HI and CO. The H$_{2}$ to HI mass ratios for this sample range from 0.2-120. The HI morphologies of the sample are consistent with that of recent HI surveys of early-type galaxies which also find a mix of HI morphologies and masses, low HI peak surface densities, and a lack of HI in early-type galaxies which reside in high density environments. The HI-detected galaxies have a wide range of HI masses (1.4$\times10^{6}$ to 1.1$\times10^{10}$ M$_{\odot}$). There does not appear to be any correlation between the HI mass and morphology (E versus S0). When HI is detected, it is centrally peaked - there are no central kpc-scale central HI depressions like those observed for early-type spiral galaxies at similar spatial resolutions and scales. A kinematic comparison between the HI 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.