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 (260 objects), volume-limited single-dish
survey of CO in normal local early-type galaxies. We find a surprisingly high
detection rate of 22%, independent of luminosity and at best weakly dependent
on environment. Second, the extent of the molecular gas is constrained with CO
synthesis imaging, and a variety of morphologies is revealed. The kinematics of
the molecular gas and stars are often misaligned, implying an external gas
origin in over a third of the systems, 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 decoupled 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.
Last, early-type galaxies do not seem to systematically obey all our usual
prejudices regarding star formation, following the standard Schmidt-Kennicutt
law but not the far infrared-radio correlation. This may suggest a greater
diversity in star formation processes than observed in disk galaxies. Using
multiple molecular tracers, we are thus starting to probe the physical
conditions of the cold gas in early-types.
