Mid-J CO emission from the Orion BN/KL explosive outflow

¹ Max-Planck-Institut für Radioastronomie (MPIfR), Auf dem Hügel 69, 53121 Bonn, Germany
² Univ. Bordeaux, LAB, UMR 5804, 33270 Floirac, France
³ CNRS, LAB, UMR 5804, 33270 Floirac, France
e-mail: Tzu-Cheng.Peng@obs.u-bordeaux1.fr
⁴ Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, 58090 Morelia, Mexico

Received: 2 July 2012
Accepted: 27 July 2012

Abstract

High spatial resolution low-J¹²CO observations have shown that the wide-angle outflow seen in the Orion BN/KL region correlates with the famous H₂ fingers. Recently, high-resolution large-scale mappings of mid- and higher-J CO emissions have been reported toward the Orion molecular cloud 1 core region using the APEX telescope. Therefore, it is of interest to investigate this outflow in the higher-J¹²CO emission, which is likely excited by shocks. The observations were carried out using the dual-color heterodyne array CHAMP⁺ on the APEX telescope. The images of the Orion BN/KL region were obtained in the ¹²CO J = 6−5 and J = 7−6 transitions with angular resolutions of $\mathrm{8}\stackrel{\mathrm{″}}{.}\mathrm{6}$ and $\mathrm{7}\stackrel{\mathrm{″}}{.}\mathrm{4}$, respectively. The results show a good agreement between our higher-J¹²CO emission and SMA low-J¹²CO data, which indicates that this wide-angle outflow in Orion BN/KL is likely the result of an explosive event that is related to the runaway objects from a dynamically decayed multiple system. From our observations, we estimate that the kinetic energy of this explosive outflow is about 1−2 × 10⁴⁷ erg. In addition, a scenario has been proposed where part of the outflow is decelerated and absorbed in the cloud to explain the lack of CO bullets in the southern part of BN/KL, which in turn induces the methanol masers seen in this region.