Discovery of shocked H2 around OH 231.8+4.2

TL;DR

This study uses advanced integral field spectroscopy to detect shocked H2 emission in the circumstellar envelope of the evolved star OH 231.8+4.2, revealing shock-related molecular hydrogen features and their spatial distribution.

Contribution

First detection of shocked H2 emission in the circumstellar envelope of OH 231.8+4.2 using integral field spectroscopy with adaptive optics.

Findings

H2 emission detected around the nebula's center and in clumps along the Western side of the Northern lobe.

H2 line ratio of 8.3+/-1.9 indicates shock excitation.

Spatial correlation between H2 emission and previously observed H-alpha emission.

Abstract

We present K-band integral field observations of the circumstellar envelope of the evolved star OH 231.8+4.2. Spatial and spectral information were simultaneously acquired using the Sinfoni integral field unit, with adaptive optics, on the Very Large Telescope. The observations reveal the discovery of H2 emission (1) around the centre of the nebula and (2) located in clumps along the Western side of the Northern lobe, presumably associated with the strong shocks that stimulate the previously reported H-alpha emission at the same location. An observed H2 1-0/2-1S(1) line ratio of 8.3+/-1.9 was calculated for the central field, a value consistent with shock excitation.