Outflow and Infall in a Sample of Massive Star‐forming Regions

Abstract

We present single-pointing observations of SiO, HCO^{+}, andH^{13}CO^{+} from the James Clerk Maxwell Telescopetoward 23 massive star-forming regions previously known to containmolecular outflows and ultracompact H II regions. We detected SiO toward14 sources and suggest that the nondetections in the other nine sourcescould be due to those outflows being older and without ongoing shocks toreplenish the SiO. We serendipitously detected SO_{ 2} toward 17sources in the same tuning as HCO^{+}. We detectedHCO^{+} toward all sources, and suggest that it is tracinginfall in nine cases. For seven infall candidates, we estimate massinfall rates between 1{\times}10^{-2} and 2{\times}10^{-5}M_{solar} yr^{-1}. Seven sources show both SiOdetections (young outflows) and HCO^{+} infall signatures. Wealso find that the abundance of H^{13 }CO^{+} tends toincrease along with the abundance of SiO in sources for which we coulddetermine abundances. We discuss these results with respect to currenttheories of massive star formation via accretion. From this survey, wesuggest that perhaps both models of ionized accretion and haltedaccretion may be important in describing the evolution of a massiveprotostar (or protostars) beyond the formation of an H II region.