The Planck Cold Clump G108.37-01.06: A Site of Complex Interplay between
  H II Regions, Young Clusters and Filaments
  The {\it Planck} Galactic Cold Clumps (PGCCs) are the possible
representations of the initial conditions and the very early stages of star
formation. With an objective to understand better the star and star cluster
formation, we probe the molecular cloud associated with PGCC G108.37-01.06
(hereafter, PG108.3), which can be traced in a velocity range $-$57 to $-$51 km
s$^{-1}$. The IPHAS images reveal H$\alpha$ emission at various locations
around PG108.3, and optical spectroscopy of the bright sources in those zones
of H$\alpha$ emission disclose two massive ionizing sources with spectral type
O8-O9V and B1V. Using the radio continuum, we estimate ionizing gas parameters
and find the dynamical ages of \hii regions associated with the massive stars
in the range 0.5$-$0.75 Myr. Based on the stellar surface density map
constructed from the deep near-infrared CHFT observations, we find two
prominent star clusters in PG108.3; of which, the cluster associated with \hii
region S148 is moderately massive ($\sim$ 240 M$\sun$). A careful inspection of
JCMT $^{13}$CO(3$-$2) molecular data exhibits that the massive cluster is
associated with a number of filamentary structures. Several embedded young
stellar objects (YSOs) are also identified in the PG108.3 along the length and
junction of filaments. We find the evidence of velocity gradient along the
length of the filaments. Along with kinematics of the filaments and the
distribution of ionized, molecular gas and YSOs, we suggest that the cluster
formation is most likely due to the longitudinal collapse of the most massive
filament in PG108.3.
