2019ApJ...877....1D

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-20 m telescope. One filament's end hosts the S242 H II region, while the other end contains Planck cold clumps. Several subregions 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 subregions (except the 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 are 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^–1 pc^–1) toward both 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 that 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.