Astron. Astrophys. 320, 594-604 (1997)
We presented near infrared broad band and narrow band images of the
S 235 A-B star forming region. Their analysis, together with
new molecular data brings to the following new picture of the
- The presence of an embedded stellar cluster in the
S 235 A-B region is confirmed. The center of the cluster
appears to be located between the two nebulosities, where the
molecular core and the youngest cluster members are located.
- Br emission occurs mainly in the vincinity
of S 235 A and B, and hot molecular hydrogen is distributed
around S 235 A, especially in a belt-like region of the
south it, at the interface between the HII region and the molecular
core. The morphology of the emission confirms that S 235 A
and B are (moderately)
evolved YSOs, that are emerging from the parental cloud.
- The driving source of the H2 O maser has been
identified on the near infrared images. On the basis of the infrared
results and the C34 S, 13 CO molecular lines
observations, the newly discovered NIR object M1 is suggested to be
the powering source of the H2 O maser. This object, which
does not coincide with any detected radio continuum source, appears to
be one of the youngest in the region and to be located in the
innermost part of the cloud core, at the center of a stellar cluster.
These characteristics suggest that the source is probably the first
manifestation of a massive YSO, a precursor of the UCHII phase.
- A large fraction of the mass of the cloud core
() has already been converted into young stars.
© European Southern Observatory (ESO) 1997
Online publication: June 30, 1998