H2O maser and a plasma obscuring torus in the radio galaxy NGC 1052

Autor: Makoto Inoue, K. M. Shibata, D. Namikawa, Seiji Kameno, Satoko Sawada-Satoh, Kayoko Nakamura
Rok vydání: 2009
Předmět:
Zdroj: Astronomische Nachrichten. 330:249-252
ISSN: 1521-3994
0004-6337
DOI: 10.1002/asna.200811168
Popis: We present multi-frequency simultaneous VLBA observations at 15, 22 and 43 GHz towards the nucleus of the nearby radio galaxy NGC 1052. These three continuum images reveal a double-sided jet structure, whose relative intensity ratios imply that the jet axis is oriented close to the sky plane. The steeply rising spectra at 15-43 GHz at the inner edges of the jets strongly suggest that synchrotron emission is absorbed by foreground thermal plasma. We detected H_2O maser emission in the velocity range of 1550-1850 km/s, which is redshifted by 50-350 km/s with respect to the systemic velocity of NGC 1052. The redshifted maser gas appears projected against both sides of the jet, similar to the HI seen in absorption. The H_2O maser gas is located where the free-free absorption opacity is large. This probably implies that the masers in NGC 1052 are associated with a circumnuclear torus or disk as in the nucleus of NGC 4258. Such circumnuclear structure can be the sense of accreting onto the central engine.
Comment: 4 pages, 5 figures, accepted for publication in Astronomische Nachrichten (issue dedicated to the Proceedings of "The 4th Workshop on Compact Steep Spectrum and GHz-Peaked Spectrum Radio Sources" held at Riccione, Italy, 26-29 May 2008)
Databáze: OpenAIRE
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