Cold Gas in Isolated Elliptical Galaxies

We selected a sample of galaxies with similar average characteristics (morphology, distance, B-band luminosity) and a strict criterion for isolation. (See Memola et al 2009). In early type galaxies, HI is rare and not correlated to the optical luminosity, as in spirals (Roberts & Haynes 1994). The HI content might be higher for those systems which result from merging. The surface density of HI in the resulting disk might be too low for a significant optical disk to form.