Active Star Formation toward the Ultracompact HiiRegions G45.12+0.13 and G45.07+0.13

A multiwavelength study of the molecular cores containing the ultracompact (UC) H II regions G45.12]0.13 and G45.07]0.13 reveals a series of phenomenological di erences that distinguish the age of these cores in terms of their development of high-mass star formation. First, we report the discovery of massive, bipolar molecular outows from both UC H II regions. The G45.12]0.13 UC H II region lies centered on a spatially extended, 6 km s~1 outow that we have mapped in the CO J The broad bipolar structure is optically thick in the 12CO line. The 13CO measurements imply a large outow mass of 4800 (12% of the total cloud mass). Interferometric observations with the Owens M _ Valley Radio Observatory (OVRO) millimeter array in the 13CO 1 ] 0 line resolve the gas into at least two outows, one of which emanates from the 4.0 Jy, 110 GHz source identied with the UC H II region. An additional outow is driven by an adjacent young, embedded object that contributes to the extended submillimeter continuum emission imaged with the CSO bolometer array camera. Lying in a separate core a few arcminutes away, the G45.07]0.13 UC H II region contains masers and pre-H 2 O sents higher velocity (11 km s~1) yet more compact CO emission. An outow has been detected in the CO 6 ] 5 transition, along with a compact submillimeter continuum source. OVRO observations in the CS J \ 2 ] 1 transition conrm a compact outow centered on the 98 GHz continuum source toward which infall is also seen in the form of redshifted absorption. The multiple outows, higher CO antenna temperatures, more extended submillimeter and radio continuum emission, and lack of masers all H 2 O distinguish the core containing G45.12]0.13 as a more advanced site of massive star formation than the neighboring core containing G45.07]0.13.