1999ApJ...527L..59I

Large-scale mapping observations of the ³P₁-³P₀ fine-structure transition of atomic carbon (C I, 492 GHz) and the J=3-2 transition of CO (346 GHz) toward the Orion A molecular cloud have been carried out with the Mount Fuji submillimeter-wave telescope. The observations cover 9 deg² and include the Orion Nebula M42 and the L1641 dark cloud complex. The C I emission extends over almost the entire region of the Orion A cloud and is surprisingly similar to that of ¹³CO (J=1-0). The CO (J=3-2) emission shows a more featureless and extended distribution than C I. The C I/CO (J=3-2) integrated intensity ratio shows a spatial gradient running from the north (0.10) to the south (1.2) of the Orion A cloud, which we interpret as a consequence of the temperature gradient. On the other hand, the C I/¹³CO (J=1-0) intensity ratio shows no systematic gradient. We have found a good correlation between the C I and ¹³CO (J=1-0) intensities over the Orion A cloud. This result is discussed on the basis of photodissociation region models.