A model for the continuum energy distribution of the ultraluminous galaxy IRAS Formula

If indeed early type galaxies used up most of their gas to form stars in atime short compared to their collapse time and if a roughly constant fractionof metals is locked up in dust grains, these galaxies may easily become opaqueto starlight and emit most of their luminosity in the far-IR. The correspondingspectral energy distribution matches remarkably well the observed continuumspectrum of the ultraluminous galaxy IRAS F$10214+4724$ from UV to sub-mmwavelengths, i.e. over almost four decades in frequency, for a galactic age$\lsim 1\,$Gyr. The bolometric luminosity in this model is $\simeq 2.7\times10^{14}\Lsol$ ($H_0 =50\,\hbox{km}\,\hbox{s}^{-1} \,\hbox{Mpc}^{-1}$, $\Omega=1$), i.e. somewhat lower than implied by previous models. In the presentframework, the bolometric luminosity of the galaxy is expected to decrease by afactor $\gsim 30$ during the subsequent evolution.Comment: TEX, 6 pages, 3 figures upon reques