We analyze the spatial distribution of dusty young stellar objects ( YSOs ) identified in the Spitzer Survey of the Orion Molecular clouds , augmenting these data with Chandra X-ray observations to correct for incompleteness in dense clustered regions .
We also devise a scheme to correct for spatially varying incompleteness when X-ray data are not available .
The local surface densities of the YSOs range from 1 pc ^ { -2 } to over 10,000 pc ^ { -2 } , with protostars tending to be in higher density regions .
This range of densities is similar to other surveyed molecular clouds with clusters , but broader than clouds without clusters .
By identifying clusters and groups as continuous regions with surface densities \geq 10 pc ^ { -2 } , we find that 59 % of the YSOs are in the largest cluster , the Orion Nebular Cluster ( ONC ) , while 13 % of the YSOs are found in a distributed population .
A lower fraction of protostars in the distributed population is evidence that it is somewhat older than the groups and clusters .
An examination of the structural properties of the clusters and groups show that the peak surface densities of the clusters increase approximately linearly with the number of members .
Furthermore , all clusters with more than 70 members exhibit asymmetric and/or highly elongated structures .
The ONC becomes azimuthally symmetric in the inner 0.1 pc , suggesting that the cluster is only \sim 2 Myr in age .
We find the star formation efficiency ( SFE ) of the Orion B cloud is unusually low , and that the SFEs of individual groups and clusters are an order of magnitude higher than those of the clouds .
Finally , we discuss the relationship between the young low mass stars in the Orion clouds and the Orion OB 1 association , and we determine upper limits to the fraction of disks that may be affected by UV radiation from OB stars or by dynamical interactions in dense , clustered regions .