Detection of a Water-Vapor Megamaser in the Active Galaxy NGC 5793
Open Access
- 1 April 1997
- journal article
- research article
- Published by Oxford University Press (OUP) in Publications of the Astronomical Society of Japan
- Vol. 49 (2) , 171-177
- https://doi.org/10.1093/pasj/49.2.171
Abstract
We have found an extragalactic water-vapor megamaser source in NGC 5793, an edge-on spiral galaxy. Its spectral profile shows two distinct high-velocity maser features, one on each side of the systemic velocity of the galaxy. They are almost symmetrically offset from the systemic velocity. The isotropic luminosity of the features is as large as 125 L⊙ at a distance of 50 Mpc. Weaker features at the systemic velocity were possibly detected. We have constructed a model which explains our observational data. The HO maser emission is emitted from a nearly edge-on circumnuclear disk, or torus, whose diameter is estimated to be larger than 4–20 pc, with a rotation velocity of Vrot = 245 km s−1 at an inferred inclination angle of 73°. The high-velocity features arise from gas at the tangential regions of the disk, or torus, and the systemic features from the region in our line of sight toward the center. In our model, the nuclear mass confined within the disk or torus is larger than 1.5 × 108M⊙.Keywords
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