Physical and Chemical Properties of the Molecular Gas Associated with the Mid-infrared Bubble S156

Abstract

Abstract Using archival infrared data of GLIMPSE, Hi-GAL, and molecular line data of SEDIGISM, MSGPCOS, and MALT90, we investigate the physical and chemical properties of the molecular gas associated with the mid-infrared bubble S156. By the method of spectral energy distribution, we made H2 column density and dust temperature maps of this region. We find two clouds with masses of 5.4 ± 1.1 × 104 M ⊙ and 2.2 ± 0.5 × 104 M ⊙, respectively. In both of the two clouds, the 13CO (2–1/1–0) and 13CO (2–1)/N2H+ (1–0) intensity ratios are enhanced on the boundary. Cloud A has a clear dust temperature gradient decreasing from the boundary to the outside region. Our analysis indicates cloud A is mainly influenced by the feedback from S156, while cloud B is affected both by S156 and the G305 complex. We also find the 13CO and C2H emissions tend to be brighter in photon dominated regions (PDRs), while N2H+ is brighter in the regions of cold gas that is far away. Furthermore, we make the abundance maps of C2H and N2H+ of cloud A. We find the abundance of C2H is enhanced in the region facing ionizing stars and it decreases steadily moving away from them. On the other hand, the abundance of N2H+ increases from the ionized boundary to the cold gas outward. These phenomena indicate C2H prefers to be produced in hot gas such as PDRs, while N2H+ could be destroyed by it. Our study also suggests the abundance ratio of C2H to N2H+ could trace PDRs in the late stages of massive star formation.