Near-infrared H 2 and continuum survey of Extended Green Objects

Abstract

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″) H 2 1-0 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 H 2 outflows (two with chains of H 2 knotty structures, five with extended H 2 bipolar structures, three with extended H 2 lobes, and two with pairs of H 2 knots). Of the 12 EGOs with H 2 outflows, three exhibit similar morphologies between the 4.5 μm and H 2 emission. However, the remaining nine EGOs show that the H 2 features are more extended than the continuum features, and the H 2 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. © 2012. The American Astronomical Society. All rights reserved..