Observational signatures of cloud-cloud collision in the extended
  star-forming region S235
  We present a multi-wavelength data analysis of the extended star-forming
region S235 (hereafter E-S235), where two molecular clouds are present. In
E-S235, using the 12CO (1-0) and 13CO (1-0) line data, a molecular cloud linked
with the site "S235main" is traced in a velocity range [-24, -18] km s^{-1},
while the other one containing the sites S235A, S235B, and S235C (hereafter
"S235ABC") is depicted in a velocity range [-18, -13] km s^{-1}. In the
velocity space, these two clouds are separated by ~4 km s^{-1}, and are
interconnected by a lower intensity intermediate velocity emission, tracing a
broad bridge feature. In the velocity channel maps, a possible complementary
molecular pair at [-21, -20] km s^{-1} and [-16, -15] km s^{-1} is also
evident. The sites, "S235ABC", East 1, and South-West are spatially seen in the
interface of two clouds. Together, these observed features are consistent with
the predictions of numerical models of the cloud-cloud collision (CCC) process,
favoring the onset of the CCC in E-S235 about 0.5 Myr ago. Deep UKIDSS
near-infrared photometric analysis of point-like sources reveals significant
clustering of young stellar populations toward the sites located at the
junction, and the "S235main". The sites, "S235ABC" harbor young compact H II
regions having dynamical ages of ~0.06-0.22 Myr, and these sites (including
South-West and East 1) also contain dust clumps (having M_clump ~40 to 635
M_sun). Our observational findings suggest that the star formation activities
(including massive stars) appear to be influenced by the CCC mechanism at the
junction.
