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tokens: to Bolatto et al. ( 2003 ). This ratio of 0.9 is consistent with the massive star-forming region in the MW (e.g., Nishimura et al. 2015 ). For source A, of and of 186 K km s −1 pc 2 yield of cm −2 (K km s −1 ) −1 . In addition, we obtained a similar from source B, cm −2 (K km s −1 ) −1 , from of and of 81 K km s −1 pc 2 . The averaged of cm −2 (K km s −1 ) −1 is four times higher than that in the MW disk, which is in good agreement with that in N83 obtained by Bolatto et al. ( 2003 ), (7.0 ± 3.4) cm −2 (K km s −1 ) −1 . 4.2. Properties of Molecular Gas and Star Formation in N83C We summarize the properties of the molecular gas based on our ALMA observations and discuss their relation to star formation in N83C. The derived gas density of cm −3 is significantly higher than the typical gas density of cm −3 in the Orion A/B molecular clouds (Nishimura et al. 2015 ), even though both gas densities are derived from the same molecular line, 12 CO(). Such a difference in derived gas densities is presumably due to the low metallicity in the SMC. The low metallicity corresponds to the small-dust content in molecular clouds, which causes the reduction of the shielding against far-UV radiation. In this condition, external far-UV radiation from the ii region associated with N83C easily penetrates and photodissociates the outer layer of the 12 CO molecule in the molecular clouds. Thus we can only observe the innermost parts of the molecular clouds, whose gas density is cm −3 , even in 12 CO emission. It is to be noted that theoretical simulations examined by Glover Clark ( 2012 ) support our results: their simulations suggest that diffuse CO emission becomes unobservable, but dense gas continues to produce observable CO emission as metallicity decreases. The observational fact that even 12 CO emission traces the high-density ( cm −3 ) regions in N83C just corresponds to this situation. Then, we consider the meaning of the derived kinetic temperature of molecular gas, 30–50 K. Bolatto et al. ( 2003 ) suggested that warm (∼40 K) clumps exist in some regions of N83 whose 12 CO()/ 12 CO() ratios exceed 2. Although the 12 CO()/ 12 CO() ratio of 0.9 in N83C is not so high (Bolatto et al. 2003 , 2005 ), it is possible that the global gas temperature exceeds 30 K in N83C considering that the bright ii region, which is a likely heating source, spreads over N83. In addition, the kinetic temperature of molecular gas is consistent with the dust temperature of 35 K (Takekoshi et al. 2017 ). Recent observational studies in the MW can also support our results: Nishimura et al. ( 2015 ) reported that the kinetic temperature in Orion A/B molecular clouds is 20–50 K, which is similar to that in the N83C, although the typical temperature of molecular clouds in the MW is 10–20 K. Considering that both N83C and Orion A/B molecular clouds are associated with bright ii regions, it is suggested that their temperature increase is due to the heating by far-UV radiation. However,