Coverage of the optical datasets used in this study. The SDSS images used in this study are represented in green, the CFHT/Megacam images in red, and the Calar Alto 1.23 m CCD observations are represented in light blue. The contour corresponding to an integrated intensity of ¹³CO of 30 K km s^-1 is represented in white. North is up and east is left. The angular scale is indicated in the lower left. Background photograph courtesy of Rogelio Bernal Andreo (DeepSkyColors.com).