Large-scale [TSUP]13[/TSUP]CO [ITAL]J[/ITAL] = 5 → 4 and [C [CSC]i[/CSC]] Mapping of Orion A

Abstract

We present maps of the 13CO J=5-->4 (551 GHz) and [C I] 3P1-->3P0 (492 GHz) emission in the Orion A molecular cloud, covering a 0.5d×2deg area. A large velocity gradient (LVG) analysis of 13CO J=5-->4 and J=1-->0 suggests that the gas temperatures in the northern part of OMC-1 (north of Δδ=-20') are ~45 K and are, on average, at least 20 K higher than those to the south. The average 13CO column density is log(N/cm-2)=16.4+/-0.3 and is fairly constant throughout the cloud, even in the low-temperature region south of BN/KL. LVG modeling of the [C I] emission shows a typical C0 column density of 2×1017 cm-2, which yields a C/CO abundance ratio in the cloud of ~0.1 (rising to levels in excess of 0.5 at the cloud edges). Comparison of the Δ-variance (which measures spatial structure in a manner similar to a power spectrum) of the Submillimeter Wave Astronomy Satellite [C I], Five College Radio Astronomy Observatory 13CO J=1-->0, and CS J=1-->0 velocity-integrated maps suggests that the [C I] and 13CO emission arise from the same gas. In contrast, the CS emission likely originates in gas that is considerably more clumpy.