Feedback of the HBe star IL Cep on nearby molecular cloud and star formation

Abstract

We present investigations of the feedback of a luminous Herbig Be star, IL Cep. We mapped the vicinity of IL Cep in the J = 1-0 transitions of 12CO, 13CO and C18O molecular lines with the Purple Mountain Observatory 13.7 m telescope. Archival data from Wide-field Infrared Survey Explorer were also employed. A parsec-scale cavity that has probably been excavated by the dominant HBe star, IL Cep, is revealed. An expanding shell-like structure featured by 12CO(J = 1-0) emission was found surrounding the cavity, which embeds several 13CO(J = 1-0) molecular clumps. The density and velocity gradients imply strong stellar winds from exciting stars, this is consistent with the morphology of molecular cloud. The 12CO(J = 1-0) spectra show broad blue wings with a width of about 3.5 km s-1. We suggest that the broad blue wings could be emission from the molecular gas shocked by stellar winds, while the main narrow component may originate from pre-shocked gas. Several bright bow-shaped rims have been detected at 12 μm, which serve as the interface of the molecular cloud facing UV dissipation from the exciting stars. The rims all have an orientation facing IL Cep, this may indicate the pre-dominant effects of IL Cep on its surroundings. A very young star candidate (about 104.8 yr) was found in the head of one bright rim, but its triggered origin is uncertain. All results achieved in this paper suggest that IL Cep has violent effects on its surroundings.