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26 April 2010
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Timothy Davis (Oxford)
'Red but not dead! - Molecular gas in early-type galaxies'
Over the past few years, early-type galaxies have shed their
"red and dead" moniker, thanks to the discovery that many host
low-level residual star formation. As part of the ATLAS3D project
we are conducting a complete, volume limited survey of the
molecular gas in 260 local early-type galaxies with the IRAM-30m
telescope and the CARMA interferometer, in an attempt to understand
the fuel powering this star formation. We find that around 23% of
early-type galaxies in the local volume host gas reservoirs, with
molecular central discs, polar structures and rings being common.
This detection rate is independent of galaxy luminosity and
environment, but does depend on the galaxy kinematics. The origin
of the molecular gas seems to depend strongly on environment, with
misaligned gas being common in the field but completely absent in
Virgo. I will discuss the kinematics and star-formation properties
of the CO detected galaxies, and the physical conditions within the
molecular gas revealed by dense/optically thin tracers such as 13CO,
HCN and HCO+. I will touch on the implications of these results in
the context of understanding star formation processes within the red
sequence. I will also present the first molecular gas Tully-Fisher
relation for early-type galaxies, and show that molecules may be the
kinematic tracer of choice for probing the M/L evolution of galaxies
over cosmic-time.
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