Molecular Gas and Star Formation in Local Early-Type Galaxies

The molecular gas content of local early-type galaxies is constrained and discussed in relation to their evolution. First, as part of the Atlas3D survey, we present the first complete, large (>250 objects), volume-limited survey of molecular gas in normal local early-type galaxies, obtained with the IRAM 30m telescope. In particular, we find a surprisingly high detection rate of 23%, independent of mass and environment, but dependent on the specific stellar angular momentum. Second, follow-up synthesis imaging with PdBI and CARMA combined with optical integral-field spectroscopy with SAURON reveals that the kinematics of the molecular gas and stars are often misaligned, implying an external gas origin in roughly half the cases overall, although this behaviour is drastically diffferent between field and cluster environments. Third, many objects appear to be in the process of forming regular kpc-size disks, and a star formation sequence can be sketched by piecing together multi-wavelength information on the molecular gas, current star formation, and young stars. Early-type galaxies with low star formation rates do not seem to systematically obey our usual prejudices regarding star formation, showing in particular significant departures from the far infrared-radio continuum correlation. This suggests a greater diversity in star formation processes than observed in disk galaxies and the possibility of "morphological quenching". Lastly, using the SMA interferometer, we present the first evidence of a large-scale AGN-driven molecular outflow in a local early-type galaxy, and discuss its relation to star formation quenching.