Molecular outflows and a mid-infrared census of the massive star formation region associated with IRAS 18507+0121

We have observed the central region of the infrared-dark cloud filament associated with IRAS 18507+0121 at millimeter wavelengths in CO( J = 1-0), (CO)-C-13( J =1-0), and (CO)-O-18( J =1-0) line emission and with Spitzer at mid-infrared wavelengths. Five massive outflows from two cloud cores were discovered. Three outflows are centered on or near an ultracompact ( UC) H II region ( G34.4+0.23), while the remaining two outflows originate from the millimeter core G34.4+0.23 MM. Modeling of the spectral energy distributions of the mid-infrared sources identified 31 young stellar objects in the filament with a combined stellar mass of similar to 127 +/- 27M circle dot. An additional 22 sources were identified as probable cluster members based on the presence of strong 24 mu m emission. The total star formation efficiency in the G34.4 cloud filament is estimated to be similar to 7%, while the massive and intermediate-mass star formation efficiency in the entire cloud filament is estimated to be roughly 2%. A comparison of the gravitational binding energy with the outflow kinetic energy suggests that the compact core containing G34.4+0.23MM is being destroyed by its molecular outflows, whereas the outflows associated with the more massive core surrounding the G34.4 UC H II region are not likely to totally disrupt the cloud. In addition, a qualitative evaluation of the region appears to suggest that stars in this region may have formed in two stages: first lower mass stars formed and then, a few Myr later, the more massive stars began to form.