regions like Orion A [@Lada:2013aa] and the Rosette Molecular Cloud [@Ybarra:2013kh].

Class II sources clearly permeate the entire complex, while Class III sources appear to have a slightly more centrally condensed distribution in the IC 1795 region but are also present in the western edge of W3-Main and surrounding the areas of low extinction to the East of W3(OH).

![image](./f5im.eps){width="6.0in"}

Two aspects are important to notice. First, cluster regions are not separated clearly in the layout of the complex, which suggest at least some partial overlap along the line of sight perpendicular to the field. Second, the spatial distribution of young sources suggest that clusters are not single, centrally condensed systems. Instead, they appear to have sub-structure.

In the following we a) make a consistent separation of the individual cluster populations and b) provide evidence of the presence of sub-structure in the cluster population by using a surface density analysis. We make the following two definitions:

1.  We define a *Principal Cluster* as a surface density structure that can be associated to a single Gaussian peak with a FWHM of at least 1.0 pc (see $\S$\[s:analysis:ss:ysodist:sss:GMM\], below).

2.  We define a *sub-structure* as a significant surface density peak, smaller than 