a) Temperature map (colours) at a time t = 24 282 yr in a grey simulation of the collapse of a 1 M_⊙ cloud. The data are presented as a function of radius and height over the mid-plane; the data have been averaged around the azimuthal direction. The black lines are logarithmically spaced density contours, in the range 10^-16<ρ< 10^-9 g cm^-3 (two contours per order of magnitude). The arrows represent the velocity vector field in the r-z plane. b) Same as for a) but using 20 frequency groups. c) Map of the logarithm of the ratio of the multigroup temperature over the grey temperature. The colour red indicates where the gas temperature in the multigroup simulation is higher than for the grey run, and vice versa for blue.