Cold gas and young stars in tidally disturbed ellipticals at z = 0

We present an analysis of the neutral hydrogen and stellar populations of elliptical galaxies in the Tal et al. sample. Our aim is to test their conclusion that the continuing assembly of these galaxies at z ~ 0 is essentially gas free and not accompanied by significant star formation. In order to do so, we make use of HI data and line-strength indices available in the literature. We look for direct and indirect evidence of the presence of cold gas during the recent assembly of these objects and analyse its relation to galaxy morphological fine structure. We find that >=25 per cent of ellipticals contain HI at the level of M(HI) >108Msolar, and that M(HI) is of the order of a few per cent of the total stellar mass. Available data are insufficient to establish whether galaxies with a disturbed stellar morphology are more likely to contain HI. However, HI interferometry reveals very disturbed gas morphology/kinematics in all but one of the detected systems, confirming the continuing assembly of many ellipticals but also showing that this is not necessarily gas free. We also find that all very disturbed ellipticals have a single-stellar-population-equivalent ag