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Aperture synthesis imaging of partially ionized gas in W48

1994; IOP Publishing; Volume: 426; Linguagem: Inglês

10.1086/174059

1538-4357

Joseph S. Onello, J. A. Phillips, P. Benaglia, W. M. Goss, Yervant Terzian,

Ionosphere and magnetosphere dynamics

view Abstract Citations (14) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Aperture Synthesis Imaging of Partially Ionized Gas in W48 Onello, Joseph S. ; Phillips, J. A. ; Benaglia, P. ; Goss, W. M. ; Terzian, Yervant Abstract We present the results of VLA observations of cool gas surrounding the H II region W48 at the H168 alpha and C168 alpha transition frequencies. Previous single-dish observations of W48 showed that the 168 alpha recombination spectrum was composed of a broad line from ionized hydrogen (H(+)) within the H II region, as well as strong, narrow lines (H(0), C(+), and S(+)) from gas outside the Stromgren sphere. High spatial resolution imaging of W48 reveals that the strong C(+) and S(+) lines arise from the stimulated amplification of the background H II region. Like the C(+) and S(+) lines, the narrow line from partially ionized hydrogen (H(0)) is strongest near the continuum peak of the H II region and suggests stimulated amplification of the line. The width of the H(0) line constrains the temperature of the partially ionized medium to be less than 200 K. However, the gas in which the H(0) line originates is found not to be spatially conincident with the carbon-emitting region. We suggest that the H(0) emission arises in the advancing ionization front of the H II region, while the C(+) and S(+) lines originate in a more extended region of the ambient molecular cloud partially ionized by photons with lambda greater than 912 A escaping the boundary of the Stromgren sphere. Publication: The Astrophysical Journal Pub Date: May 1994 DOI: 10.1086/174059 Bibcode: 1994ApJ...426..249O Keywords: Carbon; H Ii Regions; Hydrogen; Ionized Gases; Line Spectra; Molecular Clouds; Radio Astronomy; Sulfur; High Resolution; Imaging Techniques; Low Temperature; Very Large Array (Vla); Astronomy; ISM: H II REGIONS; ISM: INDIVIDUAL ALPHANUMERIC: W48; RADIO LINES: ISM full text sources ADS | data products SIMBAD (8)