Distribution of the background-diluted dust temperature for protostellar cores, which are either luminous or are low-luminosity (red and blue histograms, respectively), and for prestellar cores (gray histogram). These temperatures, which approximate the background temperature of cores, are lower than those reported in Fig. 6 for protostellar cores and higher for prestellar cores. While the background-diluted dust temperature of low-luminosity protostars and prestellar cores span a narrow range, 20 − 40 K, the one of luminous protostars is twice larger.