Observational Signatures of Cloud–Cloud Collision in the Extended Star-forming Region S235

Abstract

Abstract 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.