HERSCHEL OBSERVATIONS REVEAL ANOMALOUS MOLECULAR ABUNDANCES TOWARD THE GALACTIC CENTER

Journal Article · Sun Jan 20 04:00:00 EST 2013 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/763/1/L19· OSTI ID:22078316

Sonnentrucker, P ^[1]; Neufeld, D A; Indriolo, N ^[2]; Gerin, M; De Luca, M ^[3]; Lis, D C ^[4]

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1. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
2. Physics and Astronomy Department, Johns Hopkins University, Baltimore, MD 21218 (United States)
3. LERMA-LRA, UMR 8112 du CNRS, Observatoire de Paris, Ecole Normale Superieure, UPMC and UCP, 24 rue Lhomond, F-75231, Paris Cedex 05 (France)
4. Astronomy Department, California Institute of Technology, Pasadena, CA 91125 (United States)

We report the Herschel detections of hydrogen fluoride (HF) and para-water (p-H{sub 2}O) in gas intercepting the sight lines to two well-studied molecular clouds in the vicinity of the Sgr A complex: G-0.02-0.07 (the {sup +}50 km s{sup -1} cloud{sup )} and G-0.13-0.08 (the {sup +}20 km s{sup -1} cloud{sup )}. Toward both sight lines, HF and water absorption components are detected over a wide range of velocities covering {approx}250 km s{sup -1}. For all velocity components with V{sub LSR} > -85 km s{sup -1}, we find that the HF and water abundances are consistent with those measured toward other sight lines probing the Galactic disk gas. The velocity components with V{sub LSR} {<=} -85 km s{sup -1}, which are known to trace gas residing within {approx}200 pc of the Galactic center, however, exhibit water vapor abundances with respect to HF at least a factor three higher than those found in the Galactic disk gas. Comparison with CH data indicates that our observations are consistent with a picture where HF and a fraction of the H{sub 2}O absorption arise in diffuse molecular clouds showing Galactic disk-like abundances while the bulk of the water absorption arises in warmer (T {>=} 400 K) diffuse molecular gas for V{sub LSR} {<=} -85 km s{sup -1}. This diffuse Interstellar Medium (ISM) phase has also been recently revealed through observations of CO, HF, H{sup +}{sub 3}, and H{sub 3}O{sup +} absorption toward other sight lines probing the Galactic center inner region.

• OSTI ID: 22078316
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 763; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABSORPTION
ABUNDANCE
CARBON MONOXIDE
DETECTION
GALAXIES
HYDROGEN FLUORIDES
MOLECULES
OXONIUM IONS
VELOCITY
WATER
WATER VAPOR