Radio observations of water vapor, hydroxyl, silicon monoxide, ammonia, carbon monoxide, and compact H II regions in the vicinities of suspected Herbig-Haro objects

Systematic radio observations of 24 nebulous objects classified as Herbig-Haro (H-H) objects reveal CO, NH3, and OH lines typical of high-density molecular clouds, but no SiO masers. In nine of the regions high-velocity H2O maser emission was found, with compact radio H II regions usually within 30 arcsec of the masers; OH maser emission is generally not present in the associations of H-H objects, H2O masers, and H II regions. Models of H-H objects are discussed, and calculations indicate that high-velocity H2O masers, if interpreted as ejected fragments, may evolve into H-H objects.