Radio continuum and star formation in CO-rich early-type galaxies

In this paper we present new high- resolution Very Large Array 1.4 GHz radio continuum observations of five FIRbright CO-rich early- type galaxies and two dwarf early- type galaxies. The position on the radio- FIR correlation combined with striking agreements in morphology between high- resolution CO and radio maps show that the radio continuum is associated with star formation in at least four of the eight galaxies. The average star formation rate for the sample galaxies detected in radio is similar to 2M(circle dot) yr(-1). There is no evidence of a luminous active galactic nucleus in any of our sample galaxies. We estimate Toomre Q-values and find that the gas disks may well be gravitationally unstable, consistent with the above evidence for star formation activity. The radio continuum emission thus corroborates other recent suggestions that star formation in early- type galaxies may not be uncommon.