COMPLEX ORGANIC MOLECULES AT HIGH SPATIAL RESOLUTION TOWARD ORION-KL. II. KINEMATICS

It has recently been suggested that chemical processing can shape the spatial distributions of complex molecules in the Orion-KL region and leads to the nitrogen-oxygen 'chemical differentiation' seen in previous observations of this source. Orion-KL is a very dynamic region, and it is therefore also possible that physical conditions can shape the molecular distributions in this source. Only high spatial resolution observations can provide the information needed to disentangle these effects. Here, we present millimeter imaging studies of Orion-KL at various beam sizes using the Combined Array for Research in Millimeter-wave Astronomy. We compare molecular images with high spatial resolution images that trace the temperature, density, and kinematics of the source in order to investigate the effects of physical conditions on molecular distributions. These observations were conducted at λ = 3 mm and included transitions of ethyl cyanide [C2H5CN], methyl formate [HCOOCH3], formic acid [HCOOH], acetone [(CH3)2CO], SiO, and methanol [CH3OH]. We find differences in the molecular distributions as a function of each of the aforementioned physical factors. These results indicate that acetone may be produced by chemical processing and is robust to large changes in physical conditions, while formic acid is readily destroyed by gas-phase processing in warm and dense regions. We also find that while the spatial distributions of ethyl cyanide and methyl formate are not distinct as is suggested by the concept of 'chemical differentiation', local physical conditions shape the small-scale emission structure for these species.