Indications of inflow motions in regions forming massive stars

Observational evidence of inflowing motions in massive star-forming regions has been extremely rare. We have made a spectroscopic survey of a sample of 28 massive star-forming cores associated with water masers. An optically thick line of HCN ( 3 - 2) was used in combination with optically thin lines [(HCN)-C-13 ( 3 - 2) or (CS)-S-34 (5 - 4), (3 - 2), and (2 - 1)] to identify blue line profiles that can indicate inflow. Comparing intensities for 18 double-peaked line profiles yields 11 blue and three red profiles that are statistically significant. In the full sample of 28 sources, 12 show blue profiles, and six show red profiles that are statistically significant based on the velocity offsets of lines that are optically thick from those that are optically thin. These results indicate that HCN (3 - 2) emission may trace inflow in regions forming high-mass stars.