NEAR-IR H{sub 2} EMISSION OF PROTOSTARS: PROBING CIRCUMSTELLAR ENVIRONMENTS
- NASA Ames Research Center, M.S. 245-6, Moffett Field, CA 94035 (United States)
- Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Drive, San Francisco, CA 94132 (United States)
We present new observations of near-infrared molecular hydrogen (H{sub 2}) line emission in a sample of 18 Class I and flat-spectrum low-mass protostars, primarily in the Tau-Aur and {rho} Oph dark clouds. The line emission is extended by up to several arcseconds (several hundred AU) for most objects, and there is little night-to-night variation in line strength coincident with the continuum point source. Flux ratios of H{sub 2} v = 2-1 S(1) and v = 1-0 S(1) lines are consistent with this emission arising in jets or winds in many objects. However, most objects have only small offsets (under 10 km s{sup -1}) between their H{sub 2} and photospheric radial velocities. No objects have line ratios which are clearly caused solely by UV excitation, but the H{sub 2} emission of several objects may be caused by UV or X-ray excitation in the presence of circumstellar dust. There are several objects in the sample whose observed velocities and line fluxes suggest quiescent, non-mechanical origins for their molecular hydrogen emissions. Overall, we find the H{sub 2} emission properties of these protostars to be similar to the T Tauri stars studied in previous surveys.
- OSTI ID:
- 21474365
- Journal Information:
- Astrophysical Journal, Vol. 725, Issue 1; Other Information: DOI: 10.1088/0004-637X/725/1/1100; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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