Detection of OH absorption against PSR B1718-35

TL;DR

This paper reports the discovery of OH absorption lines against PSR B1718-35, revealing details about the interstellar medium near a star-forming region using radio observations.

Contribution

First detection of OH absorption against a pulsar at 1665 and 1667 MHz, linking it to an HII region and molecular cloud in NGC 6334.

Findings

OH absorption arises at the interface of an HII region and molecular cloud.

Beam dilution affects the observed opacity differences.

The OH cloud is approximately 3 by 1.3 parsecs in size.

Abstract

OH absorption against PSR B1718-35 at (l,b) =351.688,+0.671 has been discovered at 1665 and 1667 MHz using the Green Bank Telescope. The absorption appears to arise at the interface of an HII region and a molecular cloud which are likely associated with the high mass star forming region NGC 6334. Beam dilution is found to be the cause of differences in the opacity of the OH against the Galactic background continuum emission and against the pulsar. The OH cloud is approximately 3 by 1.3 pc and is located behind the HII region.