Bower, Geoffrey C. and Dexter, Jason and Asada, Keiichi and Brinkerink, Christiaan D. and Falcke, Heino and Ho, Paul and Inoue, Makoto and Markoff, Sera and Marrone, Daniel P. and Matsushita, Satoki and Moscibrodzka, Monika and Nakamura, Masanori and Peck, Alison and Rao, Ramprasad (2019) ALMA Observations of the Terahertz Spectrum of Sagittarius A*. The Astrophysical Journal, 881 (1). L2. ISSN 2041-8213
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Abstract
We present Atacama Large Millimeter/submillimeter Array (ALMA) observations at 233, 678, and 870 GHz of the Galactic Center black hole, Sagittarius A*. These observations reveal a flat spectrum over this frequency range with spectral index α ≈ −0.3, where the flux density S ∝ να. We model the submillimeter and far-infrared spectrum with a one-zone synchrotron model of thermal electrons. We infer electron densities n = (2–5) × 106 cm−3, electron temperatures Te = (1–3) × 1011 K, and magnetic field strength B = 10–50 G. The parameter range can be further constrained using the observed quiescent X-ray luminosity. The flat submillimeter spectrum results in a high electron temperature and implies that the emitting electrons are efficiently heated. We also find that the emission is most likely optically thin at 233 GHz. These results indicate that millimeter and submillimeter wavelength very long baseline interferometry of Sgr A* including those of the Event Horizon Telescope should see a transparent emission region down to event horizon scales.
Item Type: | Article |
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Subjects: | Euro Archives > Physics and Astronomy |
Depositing User: | Managing Editor |
Date Deposited: | 02 Jun 2023 03:58 |
Last Modified: | 04 Nov 2023 03:28 |
URI: | http://publish7promo.com/id/eprint/2629 |