Dust emissions and OH masers: evidence for tracing advanced stages of HMPOs

Abstract

We conducted a study using the Green Bank Telescope to investigate the correlation between OH masers and mm emission in high mass star forming regions (HMSFRs) using archival data from the Bolocam Galactic Plane Survey (BGPS) at 1.1 mm. Our objective was to gain insights into the physical characteristics, dynamics, and evolutionary status of these regions. Among the 27 OH maser sources examined, we found that 23 of them exhibited associations with multiple peaks of millimeter emission within a 30' radius. Notably, two high mass protostellar object candidates, namely IRAS 18089-1732 and IRAS 19035 + 0641, displayed consistent tracers. Interferometer observations further supported our findings. Compared to methanol masers, OH masers exhibited a lower level of consistency with mm sources, with a coincidence rate of 11% at offsets of 0.5 arcsec or less. At 3'' offset, 13 (48%) OH maser sources were found to be associated with mm continuum emission, with 11 previously classified as evolved HMSFRs. However, at larger offsets of 20'', the association rate increased significantly to 63%, indicating a broader spatial distribution of OH masers. This variation in offsets could be attributed to the presence of OH masers from different layers of the circumstellar disk. Our results suggest that the association between OH masers and mm emission may serve as a tracer for advanced stages of high mass protostellar objects. Future high angular resolution observations are recommended to enhance our understanding of this association.