The molecular cloud S242: physical environment and star formation activities (1707.00395v1)

Abstract: We present a multi-wavelength study to probe the star formation (SF) processes on a larger scale (~1.05 deg x 0.56 deg) around the S242 site. The S242 molecular cloud is depicted in a velocity range from -3.25 to 4.55 km/s and has spatially elongated appearance. Based on the virial analysis, the cloud is prone to gravitational collapse. The cloud harbors an elongated filamentary structure (EFS; length ~25 pc) evident in the Herschel column density map and the EFS has an observed mass per unit length of ~200 M_sun/pc exceeding the critical value of ~16 M_sun/pc (at T = 10 K). The EFS contains a chain of Herschel clumps (M_clump ~150 to 1020 M_sun), revealing the evidence of fragmentation along its length. The most massive clumps are observed at both the EFS ends, while the S242 HII region is located at one EFS end. Based on the radio continuum maps at 1.28 and 1.4 GHz, the S242 HII region is ionized by a B0.5V - B0V type star and has a dynamical age of ~0.5 Myr. The photometric 1 - 5 microns data analysis of point-like sources traces young stellar objects (YSOs) toward the EFS and the clusters of YSOs are exclusively found at both the EFS ends, revealing the SF activities. Considering the spatial presence of massive clumps and YSO clusters at both the EFS ends, the observed results are consistent with the prediction of a SF scenario of the end-dominated collapse driven by the higher accelerations of gas.