Ratios of the EQWs of the Ca ii IRT emission lines. The circle symbols represent the PMS stars in the molecular clouds and moving groups. The PMS stars are separated into two groups by the median of their FWHM_λ8542; the open circles show the group of PMS stars with a broader FWHM_λ8542 than the median. The filled circles represent the narrower group. The low-mass stars in the young open clusters IC 2391 and IC 2602 are plotted as cross symbols (Marsden et al. 2009). The dotted line represents isothermal slabs (T = 5000 K) in LTE (Herbig & Soderblom 1980; Hamann & Persson 1992). The black star symbols on the line correspond to slab optical depths of 10, 100, and 1000, beginning from the upper right. The arrow in the lower right is the redding vector with A_V = 10 mag.