HI discs in early-type galaxies

Paolo Serra (ASTRON,ATNF)

Recent work as part of the Atlas3D project demonstrates that HI is relatively common in early-type galaxies (ETGs). Both HI mass and morphology are strongly dependent on the environment of the host. In particular, 1/4 of all ETGs outside clusters host a disc (or ring) of low-column-density HI with size from a few to tens of kpc and mass form ~1e+7 to a few times 1e+9 solar masses. In this talk I will show that these gas discs are often misaligned relative to the stellar kinematics of the host based on an analysis of HI and stellar velocity fields, and I will compare for the first time these results to predictions of LCDM hydrodynamical simulations of galaxy formation.

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