High‐Resolution Imaging of the OH Megamaser Emission in IRAS 12032+1707 and IRAS 14070+0525

Abstract

We present results from Very Long Baseline Array (VLBA) observations of the 1667 and 1665 MHz OH lines in two OH megamaser galaxies, IRAS 12032+1707 and IRAS 14070+0525. For IRAS 12032+1707 we also present Arecibo H I absorption data. Almost all OH emission previously detected by single-dish observations has been recovered in IRAS 12032+1707 and is found on a compact scale of <100 pc. The emission shows an ordered velocity field that is consistent with a single disk. However, the data are also consistent with a scenario including two physically different gas components. We explore this possibility, in which the two strongest and most blue-shifted maser features are identified as the tangent points of a circumnuclear torus. The redshifted maser features would be extended in a direction perpendicular to the torus, which is in the direction of the merger companion. Thus, redshifted emission could be associated with an inflow triggered by a tidal interaction. H I absorption covers the velocities of the redshifted maser emission, suggesting a common origin. In the second source, IRAS 14070+0525, a large fraction of the OH emission is resolved out with the VLBA. We find no significant evidence of an ordered velocity field in this source, but these results are inconclusive because of a very low signal-to-noise ratio.