Acetone in Orion: high-resolution images of a special oxygen-bearing molecule
Résumé
The Orion Molecular Cloud (414 pc) is one of the most-studied astrophysical testbeds in the sky, where the interstellar medium interacts strongly with the ultraviolet radiation from the Trapezium cluster. Inside the cloud, the luminous Orion BN/KL region is well-known for its rich and complex chemistry, especially in the vicinity of the Orion hot molecular core, or Hot Core. It has been known that large oxygen- and nitrogen-bearing molecules have different distributions in this region, where N-bearing species are located near the Hot Core but O-bearing species are located close to the Orion Compact Ridge. However, (CH_3)_2CO (acetone) is one molecule which does not show this tendency. Therefore, it is of interest to carry out detailed study on the distribution of the acetone emission in the Orion BN/KL region. Our high-resolution images (1.8''× 0.8'') from the IRAM Plateau de Bure Interferometer show that the acetone emission is originated mostly from the southwest of the Hot Core and the regions close to the infrared sources IRc7 and IRc6, where the CS J=1-0 emission has been detected before. It also indicates that the acetone emission in the Orion BN/KL region is associated with dense cores in a size of a few hundred AU. We will discuss the velocity structure of the acetone emission and its physical properties in this region.