Identification of Very Red Counterparts of SiO Maser and OH/IR Objects in the GLIMPSE Survey

TL;DR

This study used Spitzer/GLIMPSE infrared data to identify and analyze very red, heavily obscured maser-emitting objects, revealing thick circumstellar matter and discovering new water fountains and nebulous sources.

Contribution

It is the first to combine IR imaging with maser observations to characterize heavily obscured evolved stars and identify new interesting objects.

Findings

All targeted objects had IR counterparts in GLIMPSE images.

Detected high-extinction layers indicating thick circumstellar matter.

Discovered new water fountains and nebulosity in specific sources.

Abstract

Using the 3.6/4.5/5.8/8.0 micron images with 1.2 arcsec pixel resolution from the Spitzer/GLIMPSE survey, we investigated 23 masing and 18 very red objects that were not identified in the 2MASS survey. Counterparts for all selected objects were found in the GLIMPSE images. Color indices in these IR bands suggest the presence of a high-extinction layer of more than a few tenths of a solar mass in front of the central star. Furthermore, radio observations in the SiO and H2O maser lines found characteristic maser-line spectra of the embedded objects, e.g., the SiO J=1-0 line intensity in the v=2 state stronger than that of the v=1 state, or very widespread H2O maser emission spectra. This indicates that these objects are actually enshrouded by very thick circumstellar matter, some of which cannot be ascribed to the AGB wind of the central star. Individually interesting objects are discussed, including two newly found water fountains and an SiO source with nebulosity.