Letter to the Editor

Red-shifted H₂O emission in NGC 3079: More evidence for a pc-scale circumnuclear torus? ^*

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
² Westerbork Observatory, PO Box 2, 7990 AA Dwingeloo, The Netherlands

Y. Hagiwara, Dwingeloo

Received: 23 January 2002
Accepted: 2 April 2002

Abstract

Using the Effelsberg 100-m telescope, sensitive measurements of the H₂O megamaser in NGC 3079 are presented. During 2000–2001, “high velocity” features are seen that are red-shifted up to 225  with respect to the systemic velocity of the galaxy (V_LSR ~ 1120 ). Symmetrically bracketing the systemic velocity, the H₂O emission covers a velocity range of ~450  with only one potential narrow gap (~20 ) near the systemic velocity itself. Velocity drifts of individual components are not convincingly detected. It is shown that the presence of red-shifted emission and the absence of detectable velocity drifts are not inconsistent with the existence of a rotating circumnuclear maser disk at the very center of the galaxy. Significant differences in the overall line profile compared to NGC 4258 and a complex morphology of the radio continuum leave, however, space for scepticism.