Line Derived Infrared Extinction toward the Galactic Center

We derive the extinction curve toward the Galactic center (GC) from 1 to 19 Delta *mm. We use hydrogen emission lines of the minispiral observed by ISO-SWS and SINFONI. The extinction-free flux reference is the 2 cm continuum emission observed by the Very Large Array. Toward the inner 14''...

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Bibliographic Details
Published in:The Astrophysical journal 2011-08, Vol.737 (2), p.73-jQuery1323904830973='48'
Main Authors: Fritz, T. K, Gillessen, S, Dodds-Eden, K, Lutz, D, Genzel, R, Raab, W, Ott, T, Pfuhl, O, Eisenhauer, F, Yusef-Zadeh, F
Format: Article
Language:English
Subjects:
Astronomy
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
DISTANCE
Earth, ocean, space
ELEMENTS
EMISSION
Exact sciences and technology
GALAXIES
HYDROGEN
NONMETALS
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Summary:We derive the extinction curve toward the Galactic center (GC) from 1 to 19 Delta *mm. We use hydrogen emission lines of the minispiral observed by ISO-SWS and SINFONI. The extinction-free flux reference is the 2 cm continuum emission observed by the Very Large Array. Toward the inner 14'' X 20'', we find an extinction of A 2.166 Delta *mm = 2.62 ? 0.11, with a power-law slope of Delta *a = --2.11 ? 0.06 shortward of 2.8 Delta *mm, consistent with the average near-infrared slope from the recent literature. At longer wavelengths, however, we find that the extinction is grayer than shortward of 2.8 Delta *mm. We find that it is not possible to fit the observed extinction curve with a dust model consisting of pure carbonaceous and silicate grains only, and the addition of composite particles, including ices, is needed to explain the observations. Combining a distance-dependent extinction with our distance-independent extinction, we derive the distance to the GC to be R 0 = 7.94 ? 0.65 kpc. Toward Sgr A* (r < 05), we obtain AH = 4.21 ? 0.10, AKs = 2.42 ? 0.10, and A L' = 1.09 ? 0.13.
ISSN:0004-637X
1538-4357
DOI:10.1088/0004-637X/737/2/73