A Catalog of Extended Green Objects (EGOs) in the GLIMPSE Survey: A new sample of massive young stellar object outflow candidates

TL;DR

This paper presents a catalog of over 300 extended green objects (EGOs) identified in the GLIMPSE survey, which are likely indicators of massive protostellar outflows, based on their infrared properties and associations.

Contribution

It provides the first large catalog of EGOs with flux measurements, linking them to massive star formation indicators like IRDCs and methanol masers.

Findings

EGOs are strongly correlated with 6.7 GHz methanol masers.

Most EGOs are associated with infrared dark clouds.

EGOs' colors match those of embedded protostars.

Abstract

Using images from the Spitzer GLIMPSE Legacy survey, we have identified more than 300 extended 4.5 micron sources (abbreviated EGO, Extended Green Object, for the common coding of the [4.5] band as green in 3-color composite IRAC images). We present a catalog of these EGOs, including integrated flux density measurements at 3.6, 4.5, 5.8, 8.0, and 24 microns from the GLIMPSE and MIPSGAL surveys. The average angular separation between a source in our sample and the nearest IRAS point source is >1 arcminute. The majority of EGOs are associated with infrared dark clouds (IRDCs), and where high-resolution 6.7 GHz methanol maser surveys overlap the GLIMPSE coverage, EGOs and 6.7 GHz methanol masers are strongly correlated. Extended 4.5 micron emission is thought to trace shocked molecular gas in protostellar outflows; the association of EGOs with IRDCs and 6.7 GHz methanol masers suggests that extended 4.5 micron emission may pinpoint outflows specifically from massive protostars. The mid-infrared colors of EGOs lie in regions of color-color space occupied by young protostars still embedded in infalling envelopes.