Identification of very red counterparts of SiO maser and OH/IR objects in the GLIMPSE survey

Abstract

Using the 3.6, 4.5, 5.8, and 8.0 μm images with 1.2″ pixel resolution of the Spitzer/GLIMPSE survey, we investigated 23 masing and 18 very red objects, which are extremely faint in the near-infrared bands. We found the counterparts for all of the selected objects on 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 H 2O 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 is stronger than that of the v = 1 state, or very widespread H 2O maser emission spectra. These facts indicate that these objects are really 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 accompanying a nebulosity. © 2007. The American Astronomical Society. All rights reserved.