Other
Scientific paper
May 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011iaus..280p.262m&link_type=abstract
The Molecular Universe, Posters from the proceedings of the 280th Symposium of the International Astronomical Union held in Tole
Other
Scientific paper
Observations of the HF J=1-0 transition with Herschel/HIFI instrument have revealed the presence of widespread absorption by hydrogen fluoride towards a variety of galactic environments (Sonnertrucker et al. 2010; Neufeld et al. 2010; Phillips et a. 2010). A spectral line strip of a region of size 2' north and south toward the massive star-forming region of Sgr B2 (M) reveals three significant features. First, absorption by foreground HF is detectable at local standard of rest (LSR) velocities in the range of -130 to 0 km s-1 at almost every observed position. This absorption is attributable to the foreground gas within the Galactocentric radii of 5 kpc. Second, small emission feature by HF is detectable at LSR velocities in the range of 90-120 km s-1 marginally extended ˜1.2pc north from Sgr B2 (M). Third, strong absorption by HF is observed at LSR velocities in the range of 60-82 km s-1 and -10-35 km s-1, related to the gas associated with Sgr B2 and the spiral arms, respectively. An analysis of this absorption yields HF abundances relative to H2 of 1-5 x 10-8, in good agreement with estimates from the chemical models which state that HF is the main reservoir of gas-phase fluorine under a wide variety of interstellar conditions (Neufeld et al. 2003; Neufeld & Wolfire 2009). Another interesting observation is that water is more abundant than hydrogen fluoride toward Sgr B2 over a wide range of velocities, in contrast to the remarkably constant H_2O/HF line ratio with average of ˜1.2 measured towards other galactic sources. The higher H_2O/HF line ratio in the 0 to 100 km s-1 LSR velocity interval could be attributed to the fact that Sgr B2 envelope shows a much extended distribution of H2O Doppler velocity space, while HF absorption spectra in that LSR velocity interval is associated to both the foreground spiral arms and the gas associated to Sgr B2.
Goldsmith Paul F.
Lis Darek C.
Monje Raquel R.
Neufeld David
Phillips Thomas G.
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