Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993aas...18311609l&link_type=abstract
American Astronomical Society, 183rd AAS Meeting, #116.09; Bulletin of the American Astronomical Society, Vol. 25, p.1467
Astronomy and Astrophysics
Astronomy
Scientific paper
Galactic H_2O masers are associated either with the circumstellar shells of late-type stars or with star-formation regions (SFR). Previous surveys for H_2O masers have revealed relatively few near the Galactic Center (GC), which is surprising since the high concentration of molecular gas there would normally be indicative of a high rate of star formation, which, in turn, would be associated with H_2O maser activity. We report on the continuation of a survey using the VLA to make 22.2 GHz observations of IRAS point sources within 2 degrees of the GC, and having 12microns or 25microns flux greater than 8 Jy. Taylor, Morris and Schulman (1993, Ap.J., in press) previously observed 97 of 342 candidate sources, detecting H_2O maser emission in 30, 7 at the GC. On October 4, 8 and 9 1993 we observed 160 more IRAS candidates at the VLA. Preliminary perusal of the data indicates a similar detection rate. We will present the results of the recent observations. The resulting H_2O maser collection consists of four source flavors: GC circumstellar sources, GC SFRs, line-of-sight circumstellar sources and line-of-sight SFRs. The GC sources are statistically distinguished from foreground sources on the basis of velocity dispersion. We assume that the high velocities of individual sources reflect the high velocity dispersion of stars and gas at the GC, whereas foreground sources should have a velocity dispersion less than a few tens of km/s. We distinguish SFR masers from circumstellar masers using their far-IR colors and H_2O spectra. The primary thrust of this work is to catalog new GC sources in order to gather new information on the galactic mass distribution and on GC star formation, but the line-of-sight sources also provide useful information on Galactic structure.
Levine Deborah Anne
Morris Mark
Schulman Eric
Taylor Geoff
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