Correlation between ∫TdV (200 pc), the integrated intensity in the 557 GHz line scaled to a distance of 200 pc, and (1000 AU), the H2 envelope density at 1000 AU. Data points are from Kristensen et al. (2012) and labeled according to their Tbol classification (filled circles =Class 0, open circles = Class 1). The borderline Class 0/1 sources according to our 557 GHz line modeling (see text) are indicated with a vertical cross. Predictions for the four models in Table 1 are represented as rectangles: red = X0, pink = S0, green = X1, blue = S1. The vertical bars illustrate the ∫TdV range for = 3.2–25 AU, and i = 30°–80°. Horizontal bars illustrate the range of (1000 AU) assuming an envelope in free fall at a rate of 1–3 times the disk accretion rate in each model.
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