Model-extrapolated molecular gas mass, assuming a single lower cutoff temperature of 49 K vs. the total molecular gas mass obtained from ﹩{L}_{\mathrm{CO}}﹩ measurements using ﹩{\alpha }_{\mathrm{CO},\mathrm{Gal}}﹩. Different symbols represent different galactic systems as indicated. The solid line is one-to-one correspondence while the dashed and dotted lines are ﹩2\times ﹩ and ﹩3\times ﹩ the value respectively.