Near-Infrared H2 and Continuum Survey of Extended Green Objects

TL;DR

This study uses high-resolution infrared imaging to analyze 34 Extended Green Objects, revealing that many exhibit H2 outflows and that their infrared emissions are often due to scattered light from young stellar objects, supporting their role as high-mass protostellar outflow candidates.

Contribution

First high-resolution infrared imaging study of EGOs linking H2 outflows with their infrared emission properties, clarifying their nature as protostellar outflow candidates.

Findings

12 out of 34 EGOs show H2 outflows.

H2 emission is often more extended than continuum emission.

Infrared emission in EGOs is partly due to scattered light from embedded YSOs.

Abstract

The Spitzer GLIMPSE survey has revealed a number of "Extended Green Objects" (EGOs) which display extended emission at 4.5 micron. These EGOs are potential candidates for high mass protostellar outflows. We have used high resolution (< 1") H2 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 H2 outflows (two with chains of H2 knotty structures; five with extended H2 bipolar structures; three with extended H2 lobes; two with pairs of H2 knots). In the 12 EGOs with H2 outflows, three of them exhibit similar morphologies between the 4.5 micron and H2 emission. However, the remaining 9 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 micron emission are similar to each other for those EGOs with K-band emission, implying that at least a part of the IRAC-band continuum emission of EGOs comes from scattered light from the embedded YSOs.