EXTENDED SUBMILLIMETER EMISSION OF THE GALACTIC CENTER AND NEAR-INFRARED/SUBMILLIMETER VARIABILITY OF ITS SUPERMASSIVE BLACK HOLE
- I. Physikalisches Institut, Universitaet zu Koeln, Zuelpicher Str. 77, 50937 Koeln (Germany)
- Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany)
- Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States)
- Instituto de Astrofisica de Andalucia, Camino Bajo del Huetor 50, 18008 Granada (Spain)
- Department of Astronomy, Kyoto University, Kyoto 6006-8502 (Japan)
- Center for Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139-4307 (United States)
- Astronomical Institute, Academy of Sciences, BocnI II, 14131 Prague (Czech Republic)
- Instituts fuer Theoretische Physic und Astrophysik, Christian-Albrechts-Universitaet zu Kiel, Leibnizstr. 15, 24118 Kiel (Germany)
- LATT, Universite de Toulouse, CNRS, 14 avenue Edouard Belin, 31400 Toulouse (France)
- Centro de AstrobiologIa (CSIC/INTA), Ctra de Torrejon a Ajalvir, km 4, 28850 Torrejon de Ardoz, Madrid (Spain)
- Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M55 3H4 (Canada)
The innermost tens of parsecs of our Galaxy are characterized by the presence of molecular cloud complexes surrounding Sgr A*, the radiative counterpart of the supermassive black hole ({approx}4 x 10{sup 6} M{sub sun}) at the Galactic center. We seek to distinguish the different physical mechanisms that dominate the molecular clouds at the Galactic center, with special emphasis on the circumnuclear disk (CND). We also want to study the energy flow and model the variable emission of Sgr A*. Our study is based on NIR and submillimeter (sub-mm) observations. Using sub-mm maps, we describe the complex morphology of the molecular clouds and the circumnuclear disk, along with their masses (of order 10{sup 5}-10{sup 6} M{sub sun}), and derive also the temperature and spectral index maps of the regions under study. We conclude that the average temperature of the dust is 14 {+-} 4 K. The spectral index map shows that the 20 and 50 km s{sup -1} clouds are dominated by dust emission. Comparatively, in the CND and its surroundings the spectral indices decrease toward Sgr A* and range between about 1 and -0.6. These values are mostly explained with a combination of dust, synchrotron, and free-free emission in different ratios. The presence of non-thermal emission also accounts for the apparent low temperatures derived in these areas, indicating their unreliability. The Sgr A* light curves show significant flux density excursions in both the NIR and sub-mm domains. We have defined a classification system to account for the NIR variability of Sgr A*. Also, we have modeled on the NIR/sub-mm events. From our modeling results we can infer a sub-mm emission delay with respect to the NIR; we argue that the delay is due to the adiabatic expansion of the synchrotron source components.
- OSTI ID:
- 21584869
- Journal Information:
- Astrophysical Journal, Vol. 738, Issue 2; Other Information: DOI: 10.1088/0004-637X/738/2/158; Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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