Discovery of shocked H2 around OH 231.8+4.2




We present K-band integral field observations of the circumstellar envelope of the evolved star OH 231.8+4.2. Spatial and spectral information was 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 Hα 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.