6.7 GHz methanol absorption toward the Seyfert 2 galaxy NGC 3079

TL;DR

This paper reports the first detection of 6.7 GHz methanol absorption in a galaxy beyond the Magellanic Clouds, revealing complex gas dynamics near the galaxy's nucleus.

Contribution

First detection of 6.7 GHz methanol absorption in an external galaxy, providing insights into molecular gas and outflows in NGC 3079.

Findings

Detected two methanol absorption features toward NGC 3079

Absorption likely occurs against nuclear radio continuum sources

Molecular gas covers the nuclear region (~4 pc)

Abstract

The detection of the 6.7 GHz line of methanol (CH3OH) is reported for the first time toward an object beyond the Magellanic Clouds. Using the Effelsberg 100 m telescope, two absorption features were identified toward the Seyfert 2 galaxy NGC 3079. Both components probably originated on lines-of-sight toward the central region, presumably absorbing the radio continuum of the nuclear sources A, B, and E of NGC 3079. One absorption feature, at the systemic velocity, is narrow and may arise from gas not related to the nuclear environment of the galaxy. The weaker blue-shifted component is wider and may trace outflowing gas. Total A-type CH3OH column densities are estimated to be between a few times 10^13 and a few times 10^15 cm^-2. Because of a highly frequency-dependent continuum background, the overall similarity of HI, OH, and CH3OH absorption profiles hints at molecular clouds that cover the entire area occupied by the nuclear radio continuum sources ~ 4 pc.