Observational signatures of end-dominated collapse in the S242
  filamentary structure
  We present new CO (13CO(1-0) and C18O(1-0)) and CS(2-1) line observations of
an elongated filamentary structure (length ~30 pc) in the star-forming site
S242, which were taken with the OSO-20m telescope. One filament's end hosts the
S242 HII region, while the other end contains Planck cold clumps. Several
sub-regions are identified in the filament, and are supersonic with Mach number
of 2.7-4.0. The study of the dynamical states shows supercritical nature of the
sub-regions (except central part), which could not be supported by a
combination of thermal and turbulent motions. Young stellar objects are seen
toward the entire filament, but more concentrated toward its ends. Dense
molecular cores are observed mainly toward the filament ends, and are close to
virial equilibrium. Position-velocity plots trace velocity gradients (~1
km/s/pc) toward both the ends. An oscillatory pattern in velocity is also
observed toward the filament, indicating its fragmentation. The collapse
timescale of the filament is computed to be ~3.5 Myr. Using the 13CO data, the
structure function in velocity of the filament is found to be very similar as
seen in the Musca cloud for lags ~1-3 pc, and deviates from the Larson's
velocity-size relationship. The observed oscillatory pattern in the structure
function at higher lags suggests the existence of large-scale and ordered
velocity gradients as well as the fragmentation process through accretion along
the filament. Considering all the observed results along with their
uncertainties, the S242 filament is a very good example of the end-dominated
collapse.
