Probing the Obscuring Medium Around Active Nuclei Using Masers: The Case of 3C 403 |
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Authors: | A. Tarchi C. Henkel M. Chiaberge K. M. Menten A. Brunthaler L. Moscadelli |
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Affiliation: | (1) Istituto di Radioastronomia, CNR, Via Gobetti 101, Bologna, Italy;(2) INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, Capoterra (CA), Italy;(3) Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, Bonn, Germany;(4) JIVE, Joint Institute for VLBI in Europe, AA Dwingeloo, The Netherlands |
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Abstract: | We report the first detection of a water megamaser in a radio-loud galaxy, 3C 403, and present a follow-up study using the VLA. 3C 403 has been observed as a part of a small sample of FR II galaxies with evidence of nuclear obscuration. The isotropic luminosity of the maser is 1200 L. With a recessional velocity of cz 17680 km s–1 it is the most distant water maser so far reported. The line arises from the densest (> 108 cm–3) interstellar gas component ever observed in a radio-loud galaxy. Two spectral features are identified, likely bracketing the systemic velocity of the galaxy. Our interferometric data clearly indicate that these arise from a location within 0.1 (110 pc) from the active galactic nucleus. We conclude that the maser spots are most likely associated with the tangentially seen parts of a nuclear accretion disk, while an association with dense warm gas interacting with the radio jets cannot yet be ruled out entirely. |
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Keywords: | 3C 403 active galaxies masers |
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