2017ApJ...849...65D

We present a multi-wavelength data analysis of the extended star-forming region S235 (hereafter E-S235), where two molecular clouds are present. In E-S235, using the ¹²CO (1-0) and ¹³CO (1-0) line data, a molecular cloud linked with the site "S235main" is traced in a velocity range [-24, -18] km s^–1, while the other one containing the sites S235A, S235B, and S235C (hereafter "S235ABC") is depicted in a velocity range [-18, -13] km s^–1. In the velocity space, these two clouds are separated by ∼4 km s^–1, and are interconnected by a lower-intensity intermediate velocity emission, tracing a broad bridge feature. In the velocity channel maps, a possible complementary molecular pair at [-21, -20] km s^–1 and [-16, -15] km s^–1 is also evident. The sites, "S235ABC," east 1, and south-west, are spatially seen in the interface of two clouds. Together, these observed features are consistent with the predictions of numerical models of the cloud-cloud collision (CCC) process, favoring the onset of the CCC in E-S235 about 0.5 Myr ago. Deep UKIDSS near-infrared photometric analysis of point-like sources reveals significant clustering of young stellar populations toward the sites located at the junction, and the "S235main." The sites "S235ABC" harbor young compact H II regions with dynamical ages of ∼0.06-0.22 Myr, and these sites (including south-west and east 1) also contain dust clumps (having M_clump ∼ 40 to 635 M_☉). Our observational findings suggest that the star formation activities (including massive stars) appear to be influenced by the CCC mechanism at the junction.