Grain alignment in starless cores (Jones et al. 2015, AJ, 149, 31). The line labeled Pmax is the maximum polarization in transmission for perfect grain alignment with the magnetic field
in the plane of the sky. The line labeled JKD includes the effects of turbulence, and fits the main trend in the ISM. The small plus marks and solid squares are measurements of  stars
shining through starless cores from behind. The show a further decline in polairzation efficiency (P/Tau) at higher Av than can be explained by turbulence alone. The trend is shown as
a dashed line from a power-law fit by Whitett et al. (2008, ApJ, 674, 304). The open circles are submm observations of fractional polarization scaled to match the high extinction end
of  the trend in stellar polarization (Jones, 2015). A model invoking loss of alignment with optical depth is shown as a solid line.