Other
Scientific paper
Jan 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995phdt........34c&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF MARYLAND COLLEGE PARK, 1995.Source: Dissertation Abstracts International, Volume: 57-03, Section:
Other
1
Circumnuclear Disk
Scientific paper
16-45 μm spectra of the central 80" of the Galaxy have been obtained using the Goddard Cryogenic Grating Spectrometer #2 on the Kuiper Airborne Observatory. A broad band of excess emission extending from 24 to 45 μm is present in the spectra of those positions covering the "tongue" and the inner edge of the circumnuclear disk. A similar emission dust feature has only been observed in some carbon -rich evolved stars, and therefore, this is the first time this emission dust feature has been observed in the interstellar medium. The origin of this 30 μm feature dust in the Galactic Center is unknown. We propose that it is due to either dust condensed from the ejecta of past supernovae or from the ejected mass of evolved massive stars. We find that the dust properties in the "tongue" and the inner edge of the circumnuclear disk are different from the cavity, so that we speculate they are now falling towards the Galactic Center. Two kinds of energy sources are argued to be responsible for the dust heating in the Galactic Center: (1) the IRS sources are the cause of the hot dust components (140-301 K), and they are distributed throughout the cavity; (2) a He I emission line star cluster is the energy source of the warm dust component (59-91 K) in the central 3 pc. We find a lower limit of ~1 times 10^6L _odot for the He I emission line star cluster. We find that the line of sight extinction across the cavity is not uniform. It is diminished and roughly constant in the northeastern side of the cavity, but increases to the southwestern side. From the other observations we find that there is a cool dust component of 40 K in the central 30". Based on these results we propose that there is a cool dust envelope with non-uniform distribution covering the cavity of the Galactic Center. Finally, our results here support the view that the southwestern side of the circumnuclear disk is in front of its northeastern side.
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