Star formation around mid-infrared bubble N37: Evidence of cloud-cloud
  collision
  We have performed a multi-wavelength analysis of a mid-infrared (MIR) bubble
N37 and its surrounding environment. The selected 15$' \times$15$'$ area around
the bubble contains two molecular clouds (N37 cloud; V$_{lsr}\sim$37-43 km
s$^{-1}$, and C25.29+0.31; V$_{lsr}\sim$43-48 km s$^{-1}$) along the line of
sight. A total of seven OB stars are identified towards the bubble N37 using
photometric criteria, and two of them are spectroscopically confirmed as O9V
and B0V stars. Spectro-photometric distances of these two sources confirm their
physical association with the bubble. The O9V star is appeared to be the
primary ionizing source of the region, which is also in agreement with the
desired Lyman continuum flux analysis estimated from the 20 cm data. The
presence of the expanding HII region is revealed in the N37 cloud which could
be responsible for the MIR bubble. Using the $^{13}$CO line data and
photometric data, several cold molecular condensations as well as clusters of
young stellar objects (YSOs) are identified in the N37 cloud, revealing ongoing
star formation (SF) activities. However, the analysis of ages of YSOs and the
dynamical age of the HII region do not support the origin of SF due to the
influence of OB stars. The position-velocity analysis of $^{13}$CO data reveals
that two molecular clouds are inter-connected by a bridge-like structure,
favoring the onset of a cloud-cloud collision process. The SF activities (i.e.
the formation of YSOs clusters and OB stars) in the N37 cloud are possibly
influenced by the cloud-cloud collision.
