I have presented a multi-transition CS study of a dense core in a galactic cirrus cloud. This core harbours three dense low-mass condensations ( ). The spectra of the southernmost condensation show the double-peaked self-absorbed features which are thought to be characteristics of inward motion in a molecular cloud (e.g. Zhou 1992; Myers et al. 1996). A search for a compact dust source and observations of other CS lines or other high-density tracer at higher angular resolution will help to understand the nature of the motions and allow to model the density structure of this condensation.
If the scenario presented here holds true, the observations
indicate that even in gravitationally unbound clouds there can be
localized regions where the turbulent motions are small and a
gravitationally bound core can form, possibly leading to star
formation. The stars that might be born in these dense cores will be
very low-mass objects, close to the brown dwarf mass-limit. Systematic
searches for compact dust sources and further kinematic evidence for
inward motion will also shed light on the time-scales and on the
mechanisms that lead to the onset of low-mass star-formation.
© European Southern Observatory (ESO) 1999
Online publication: September 2, 1999