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| EPoS Contribution |
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A New Sample of Massive Young Stellar Object Outflow Candidates: Extended Green Objects (EGOs) from the GLIMPSE Survey
Claudia J. Cyganowski University of Wisconsin-Madison, Madison, WI, USA | |
| A promising new diagnostic for identifying actively accreting massive young stellar objects (MYSOs) has emerged from large-scale Spitzer surveys of the Galactic plane: extended emission in the IRAC 4.5 micron band, believed to trace shocked molecular gas in active protostellar outflows. I will discuss the GLIMPSE catalog of extended 4.5 micron sources (called EGOs, Extended Green Objects, for the common coding of the [4.5] band as green in 3-color composite IRAC images) and the evidence that EGOs, as a population, are massive YSOs. I will present the results of high-resolution EVLA surveys of 20 EGOS in the 6.7 GHz Class II and 44 GHz Class I methanol maser transitions, which respectively trace high-mass protostars and molecular outflows, and a JCMT survey in the molecular outflow tracers HCO+ and SiO. High detection rates of all outflow tracers and the spatial distribution of the masers with respect to the midinfrared emission provide convincing evidence that the surveyed EGOs are much-sought MYSOs which are actively accreting and driving outflows. I complement the survey results with detailed case studies of two EGOs using SMA and CARMA data. The high-resolution mm observations reveal bipolar molecular outflows coincident with the 4.5 micron lobes in both sources. Strong SiO(2-1) emission is also detected, confirming that the extended 4.5 micron emission traces recently shocked gas in active outflows. While a single dominant outflow is identified in each of the studied EGOs, the mm data show that one of the EGOs is associated with at least three compact cores, and may be a protocluster. | |
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| Caption: Three-color Spitzer images (3.6 micron blue, 4.5 micron green, 8.0 micron red) of two EGOs overlaid with contours of 1.3 mm continuum emission (black) and high velocity 12 CO(2-1) emission from the SMA. (a) G11.92-0.61. Though multiple compact cores are present, there is one dominant outflow. (b) G19.01-0.03. 12 CO (2-1) emission nearer the systemic velocity is dominated by an extended envelope, indicating that the source is very young. | |
| Collaborators: E. Churchwell, U Wisconsin-Madison, USA C. L. Brogan, NRAO, USA T. R. Hunter, NRAO, USA Q. Zhang, CfA, USA |
Key publication
Suggested Session: Massive Stars, Molecular Clouds |