Molecular Outflows and a Mid-Infrared Census of the Massive Star Formation Region Associated with IRAS 18507+0121

Creators: Shepherd, D. S.; Povich, M. S.; Whitney, B. A.; Robitaille, T. P.; Nürnberger, D. E. A.; Bronfman, L.; Stark, D. P.; Indebetouw, R.; Meade, M. R.; Babler, B. L.

Abstract

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), ^(13)CO(J = 1-0), and C^(18)O(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 ~127 ± 27 M_☉. An additional 22 sources were identified as probable cluster members based on the presence of strong 24 μm emission. The total star formation efficiency in the G34.4 cloud filament is estimated to be ~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+0.23 MM 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.

Additional Information

© 2007 American Astronomical Society. Print publication: Issue 1 (2007 November 1); received 2007 March 5; accepted for publication 2007 June 28. D. S. S. would like to thank Allison Sills for useful discussions on properties of young clusters. Research at the Owens Valley Radio Observatory is supported by the National Science Foundation through NSF grant AST 96-13717. Star formation research at Owens Valley is also supported by NASA's Origins of Solar Systems program, grant NAGW-4030, and the Norris Planetary Origins Project. L. B. acknowledges support from the Chilean Center for Astrophysics FONDAP grant 15010003. Support for GLIMPSE, part of the Spitzer Space Telescope Legacy Science Program, was provided by NASA through contracts 1224653 (University of Wisconsin at Madison) and 1224988 (Space Science Institute). B. W. gratefully acknowledges support from the NASA Astrophysics Theory Program (NNG 05-GH35G) and the Spitzer Space Telescope Theoretical Research Program (subcontract 1290701).

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