We present new multicolor photopolarimetry of stars behind the Southern Coalsack. Analyzed together with multiband polarization data from the literature, probing the Chamaeleon I, Musca, rho Opiuchus, R CrA, and Taurus clouds, we show that the wavelength of maximum polarization ({lambda}max) is linearly correlated with the radiation environment of the grains. Using far-infrared emission data, we show that the large scatter seen in previous studies of {lambda}max as a function of Av is primarily due to line-of-sight effects causing some Av measurements to not be a good tracer of the extinction (radiation field strength) seen by the grains being probed.

Cone search capability for table J/ApJ/665/369/table2 (Coalsack Polarimetry Results)

Cone search capability for table J/ApJ/665/369/table4 (Stars with data from archives and the literature)