Enclosed projected mass per unit length as a function of enclosing width w, for the ISF and L1641, shown separately. As in Fig. 4, the east and west subsets are shown separately (after multiplying by 2). The ISF is extremely well approximated by a pure power law, which is explicitly indicated as a red line. L1641 shows the same power law (both slope and normalization) for 2.5 pc ≲ w< 8.5 pc, but the surface density falls off substantially more slowly in the inner 2.5 pc.