!! Salle de Conférences du Bat B !!, Observatoire de Paris
The Large Scale Structure of the Taurus Molecular Cloud -
What Really Controls Star Formation?
Paul F.GOLDSMITH
JPL/Caltech
Résumé :
The importance of star formation has led to many instrumental
advances, major observational efforts, and significant
progress in understanding the small-scale structures from
which stars form. These dense cores contain only a small
fraction of the mass of the molecular clouds within which
they are embedded, and studies suggest that the rate of
star formation is primarily controlled by the rate at which
molecular clouds are formed and at which gas passes from low
to high density, with the latter situation leading to gravitational
collapse on a rapid timescale. To understand the earlier phases
leading to star formation, we have obtained fully sampled maps
in 12CO and 13CO of the Taurus Molecular Cloud, one of the neares
t and best studied star forming regions. The maps each
contain ~3 million spectra and thus have unprecedented
spatial dynamic range, which lets us see a broad range
of structures and kinematic features connecting large
and small scales over a factor of 1000 in size.
We have used this data to study in detail the column
density distribution, and have determined the total mass
of the region to be ~ 20,000 solar masses, almost a factor
of 3 larger than previously obtained. This is a result
of the presence of large amounts of low column density gas
in which the CO abundance is considerably less than generally
assumed. The resulting star formation efficiency
(stellar mass/total mass) is thus reduced to between 0.3
and 1.2 percent. We also touch on the kinematics of the gas,
the dust and gas distributions in the region, and the relationship
between the gas and the magnetic field in the region.
