Diagnostic two-phase gas ratios as a function of the observed [ CI ] (2−1)/(1−0) line flux ratio. The left panel shows the behavior of the ‘warm/cold/ratio of total CO line luminosities, taken from Kamenetzky et al. (2014) versus the [ CI ] line ratio from this paper. The center panel shows the corresponding “warm/cold” ratio of molecular gas masses. The right panel shows the fraction of the ¹²COJ = 2−1 flux that is ascribed to “dense” gas, based on the results published by Israel (2009b, and references therein). All three quantities increase in favor of “warm” and “dense” with increasing [ CI ] line flux ratio.