Peak optical depth of the water ice (τ_3.0) plotted against the visual extinction on the line of sight (A_V). The three panels are all identical, but the area shown is smaller going from left to right. The enlarged areas are shown by dotted lines in the left panels. The canonical relation between τ_3.0 and A_V in Taurus found by Whittet et al. (2001) is shown by dashed lines. The measurements toward the Pipe Nebula are shown by filled yellow circles. Other measurements shown in the panels are from star-forming regions such as Taurus (Whittet et al. 1988; Smith et al. 1993; Murakawa et al. 2000), Lupus (Boogert et al. 2013), and IC 5146 (the Cocoon Nebula, Chiar et al. 2011). Two starless cores, L 183 (Whittet et al. 2013), L 429 (Boogert et al. 2011), and the globules in the Southern Coalsack (Smith et al. 2002) are shown as well. The linear regression fit to the data points from the Pipe Nebula is depicted by the gray line. Filled gray circles are the same as yellow circles, but after reducing A_V by 25% from those in Román-Zúñiga et al. (2010).