RADEX calculations on modeling the line ratios toward the peak position in region C2 (α_J2000 = 22^h17^m27^s.4, δ_J2000 = 61°42′42′′) indicated by the cross in Figs. 12c and d. (a) The modeled line ratios, (red) and (blue), as a function of kinetic temperature and H₂ number density. The solid lines and the dotted lines represent the observed line ratios and their 1σ uncertainties for and . The shadowed region in the intersection represents χ² <2.3, corresponding to the 1σ range. (b) The modeled as a functionof H₂ number density at a given kinetic temperature of 21 K.