High-resolution Imaging of the OH Megamaser Emission in IRAS12032+1707 and IRAS14070+0525

TL;DR

This study uses VLBA and Arecibo observations to analyze OH megamaser emissions in two galaxies, revealing compact emission regions, potential torus structures, and complex gas dynamics related to galaxy interactions.

Contribution

First high-resolution imaging of OH megamasers in IRAS12032+1707 and IRAS14070+0525, exploring their gas structures and kinematics with implications for galaxy merger processes.

Findings

IRAS12032+1707's emission is on a <100 pc scale with a possible disk or torus structure.

Redshifted maser features may be linked to inflow caused by tidal interactions.

IRAS14070+0525 shows unresolved emission with no clear velocity pattern due to low SNR.

Abstract

We present results from VLBA observations of the 1667 and 1665 MHz OH lines in the two OH megamaser galaxies IRAS12032+1707 and IRAS14070+0525. For IRAS12032+1707 we also present Arecibo HI absorption data. Almost all OH emission previously detected by single dish observations has been recovered in IRAS12032+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 is also consistent with a scenario including two physically different gas components. We explore this possibility, in which the two strongest and most blueshifted 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. HI absorption covers the velocities of the redshifted maser emission, suggesting a common origin. In the second source, IRAS14070+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 due to a very low signal-to-noise ratio.