\subsection{Near-Infrared Extinction Map from 2MASS}
We use the extinction map presented in \citet{Ridge_2006} and \citet{Alves_2006}, made by applying the Near-Infrared Color Excess Revisited technique (NICER; \citet{Lombardi_2001}) to the Two Mircon All-Sky Survey (2MASS) point source catalog. The resulting K-band extinction is then converted to V-band extinction by the relation $A_K = 0.112 A_V$ (\citet{Rieke_1985}). The derived extinction map has a fixed resolution of 3$'$, with a Nyquist-sampled pixel size of 1.5$'$. The map is made public on the COordinated Molecular Probe Line Extinction Thermal Emission (COMPLETE) project website. 

The 2MASS/NICER extinction map is accurate up to $A_V \simeq$ 10 mag, limited by the number of background stars that can be used to derive the extinction. The confusion of more evolved YSOs embedded in the cloud with the background stars (with their J, H, and K band colors in the same range) limits the accuracy of the extinction on the low end. See \S3.4 for more details on how we deall with these limits and the related data editing.