in all bands. a) $J-H$ vs. $K-[4.5]$ two-color diagram. The solid curve is a model for dwarf main sequence population from the Dartmouth [@Dotter:2008aa] grid; the solid line at its right side is the Classic T-Tauri star locus [@Meyer:1997aa] adapted to this color space as in @Teixeira:2012aa. b) \[3.6\]-\[4.5\] vs. \[4.5\]-\[8.0\] two-color diagram, showing a clear separation between evolutionary classes.[]{data-label="fig:diagrams"}](f4b.pdf "fig:"){width="3.0in"}

Dust Extinction and the Spatial Distribution of YSOs \[analysis:extmap\]
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In Figure \[fig:ysodist\] we plot the spatial distribution of the YSOs on a dust extinction map. This dust extinction (A$_V$) map for the DR15 region was constructed with the near-IR catalog an optimized version of the near-infrared excess (NICER) algorithm of @Lombardi:2001aa, which estimates extinction using the dust-reddened colors of stars in the background of the cloud. In order to construct the map, we removed all sources with colors indicative of intrinsic infrared excess, which would bias the estimated extinction towards higher values. We used a sigma-clipping scheme to remove outlier values from the final weighted averages at each position. The map was constructed using Nyquist sampling on a equally spaced equatorial grid, smoothing the individual extinction estimates of background stars with a Gaussian filter of 30$\arcsec$ FWHM (this 