A multi-wavelength study of star formation activity in the S235 complex
  We have carried out an extensive multi-wavelength study to investigate the
star formation process in the S235 complex. The S235 complex has a sphere-like
shell appearance at wavelengths longer than 2 $\mu$m and harbors an O9.5V type
star approximately at its center. Near-infrared extinction map traces eight
subregions (having A$_{V}$ $>$ 8 mag), and five of them appear to be
distributed in an almost regularly spaced manner along the sphere-like shell
surrounding the ionized emission. This picture is also supported by the
integrated $^{12}$CO and $^{13}$CO intensity maps and by Bolocam 1.1 mm
continuum emission. The position-velocity analysis of CO reveals an almost
semi-ring like structure, suggesting an expanding H\,{\sc ii} region. We find
that the Bolocam clump masses increase as we move away from the location of the
ionizing star. This correlation is seen only for those clumps which are
distributed near the edges of the shell. Photometric analysis reveals 435 young
stellar objects (YSOs), 59\% of which are found in clusters. Six subregions
(including five located near the edges of the shell) are very well correlated
with the dust clumps, CO gas, and YSOs. The average values of Mach numbers
derived using NH$_{3}$ data for three (East~1, East~2, and Central~E) out of
these six subregions are 2.9, 2.3, and 2.9, indicating these subregions are
supersonic. The molecular outflows are detected in these three subregions,
further confirming the on-going star formation activity. Together, all these
results are interpreted as observational evidence of positive feedback of a
massive star.
