The contours show the distributions of the maximum likelihood for a given density and temperature in the single-component LVG fitting. Contours are drawn from 0.1 to 0.9 by 0.2. Background gray scale levels show the velocity gradient associated with the best LVG fitting results, for each given temperature and density. The dashed lines indicate the thermal pressure log (n_H2×T_kin) in units of K cm^-3.