Dust temperature estimated by including additional heating sources. The purple dashed line displays the initial estimate of the dust temperature as given by Hollenbach et al. (1991). The black solid line is the dust temperature that takes into account the depth dependence of infrared radiation by using a simple scaling with opacity. The red dot-dashed line also considers the gas-grain heating for which the variables Λ_gg and n_H are fixed here to serve in this example.