In this paper we present a novel method to identify and characterize stellar
clusters deeply embedded in a dark molecular cloud. The method is based on
measuring stellar surface density in wide-field infrared images using star
counting techniques. It takes advantage of the differing H-band luminosity
functions (HLFs) of field stars and young stellar populations and is able to
statistically associate each star in an image as a member of either the
background stellar population or a young stellar population projected on or
near the cloud. Moreover, the technique corrects for the effects of
differential extinction toward each individual star. We have tested this method
against simulations as well as observations. In particular, we have applied the
method to 2MASS point sources observed in the Orion A and B complexes, and the
results obtained compare very well with those obtained from deep Spitzer and
Chandra observations where presence of infrared excess or X-ray emission
directly determines membership status for every star. Additionally, our method
also identifies unobscured clusters and a low resolution version of the Orion
stellar surface density map shows clearly the relatively unobscured and diffuse
OB 1a and 1b sub-groups and provides useful insights on their spatial
distribution.Comment: A&A, in press; 13 pages, multi-layer figures can be displayed with
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