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arXiv · 0902.4068

H_2O maser and a plasma obscuring torus in the radio galaxy NGC 1052

S. Sawada-Satoh·S. Kameno·K. Nakamura·D. Namikawa·K. M. Shibata·M. Inoue
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Abstract

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.

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S. Sawada-Satoh, S. Kameno, K. Nakamura, D. Namikawa, K. M. Shibata, M. Inoue. 2009-02-24. H_2O maser and a plasma obscuring torus in the radio galaxy NGC 1052. https://doi.org/10.1002/asna.200811168

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