2012ApJS..200....2L

The Spitzer GLIMPSE survey has revealed a number of "Extended Green Objects" (EGOs) that display extended emission at 4.5 µm. These EGOs are potential candidates for high-mass protostellar outflows. We used high-resolution (<1'') H₂1-0 S(1) line, K-, and H-band images from the United Kingdom Infrared Telescope to study 34 EGOs to investigate their nature. We found that 12 EGOs exhibit H₂ outflows (two with chains of H₂knotty structures, five with extended H₂ bipolar structures, three with extended H₂lobes, and two with pairs of H₂knots). Of the 12 EGOs with H₂outflows, three exhibit similar morphologies between the 4.5 µm and H₂emission. However, the remaining nine EGOs show that the H₂ features are more extended than the continuum features, and the H₂ emission is seldom associated with continuum emission. Furthermore, the morphologies of the near-infrared continuum and 4.5 µm emission are similar to each other for those EGOs with K-band emission, implying that at least part of the IRAC-band continuum emission of EGOs comes from scattered light from the embedded young stellar objects.