Ethynyl around the HII regions S255 and S257

Abstract

We present the results of the ethynyl (C 2 H) emission line observations towards the H regions S255 and S257 and the molecular cloud between them. Radial profiles of line brightness, column density, and abundance of C 2 H are obtained. We show that the radial profile of the ethynyl abundance is almost flat towards the H regions and drops by a factor of two towards the molecular cloud. At the same time, we find that the abundance of ethynyl is at maximum towards the point sources in the molecular cloud -the stars with emission lines or emitting in X-ray. The line profiles are consistent with the assumption that both H regions have front and back neutral walls that move relative to each other.

The link between gas and stars in the S254-S258 star-forming region

“…At present, only the brightest molecular condensations with embedded clusters S255N, S255-IR, and S255S were mapped with high-density gas tracing molecular lines (Cyganowski et al 2007;Wang et al 2011;Zinchenko et al 2012Zinchenko et al , 2015Zemlyanukha et al 2018). The expansion of the H II regions S255 and S257 (observed recently by e. g. Buslaeva et al 2021) and compressing the material "sandwiched" between these H II regions may explain a large amount of high-density gas and active star formation in the S255-IR region (Minier et al 2007). Other molecular condensations with embedded clusters have not been studied yet in the high-density gas tracers.…”