MUNA Lunch Talk:
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.
December 14
12:10PM, Room 230, NRAO, Edgemont Road