A WATER MASER AND NH{sub 3} SURVEY OF GLIMPSE EXTENDED GREEN OBJECTS
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794 (United States)
- Department of Physics and Astronomy, University of British Columbia, Okanagan, Kelowna BC V1V 1V7 (Canada)
- Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)
- Department of Astronomy, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
We present the results of a Nobeyama 45 m H{sub 2}O maser and NH{sub 3} survey of all 94 northern GLIMPSE extended green objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5 {mu}m emission. We observed the NH{sub 3}(1,1), (2,2), and (3,3) inversion lines, and detected emission toward 97%, 63%, and 46% of our sample, respectively (median rms {approx} 50 mK). The H{sub 2}O maser detection rate is 68% (median rms {approx} 0.11 Jy). The derived H{sub 2}O maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on mid-infrared (MIR) properties or maser associations. H{sub 2}O masers and warm dense gas, as indicated by emission in the higher-excitation NH{sub 3} transitions, are most frequently detected toward EGOs also associated with both Class I and II CH{sub 3}OH masers. Ninety-five percent (81%) of such EGOs are detected in H{sub 2}O (NH{sub 3}(3,3)), compared to only 33% (7%) of EGOs without either CH{sub 3}OH maser type. As populations, EGOs associated with Class I and/or II CH{sub 3}OH masers have significantly higher NH{sub 3} line widths, column densities, and kinetic temperatures than EGOs undetected in CH{sub 3}OH maser surveys. However, we find no evidence for statistically significant differences in H{sub 2}O maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1 mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic H{sub 2}O maser luminosity and clump number density. H{sub 2}O maser luminosity is weakly correlated with clump (gas) temperature and clump mass.
- OSTI ID:
- 22167797
- Journal Information:
- Astrophysical Journal, Vol. 764, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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