Filamentary Structure in the Orion Molecular Cloud.

We present a large scale sup 13 CO map (containing 33,000 spectra on a 1' grid) of the giant molecular cloud located in the southern part of Orion which contains the Orion Nebula, NGC1977, and the L1641 dark cloud complex. The overall structure of the cloud is filamentary, with individual features having a length up to 40 times their width. The northern portion of the cloud is compressed, dynamically relaxed, and supports massive star formation. In contrast, the southern part of the Orion A cloud is diffuse, exhibits chaotic spatial and velocity structure, and supports only intermediate to low mass star formation.