A Model for the Spectral Energy Distribution of the Ultraluminous Galaxy IRAS F10214+4724

If indeed early type galaxies used up most of their gas to form stars in a time short compared to their collapse time and if a roughly constant fraction of metals is locked up in dust grains, these galaxies may easily become opaque to starlight and emit most of their luminosity in the far-IR. The corresponding spectral energy distribution matches remarkably well the observed continuum spectrum of the ultraluminous galaxy IRAS F$10214+4724$ from UV to sub-mm wavelengths, i.e. over almost four decades in frequency, for a galactic age $\text{lsim}1$Gyr. The bolometric luminosity in this model is $\simeq 2.7\times 10^{14}\Lsol$($H_0 =50,\hbox{km},\hbox{s}^{-1} ,\hbox{Mpc}^{-1}$,$\Omega =1$), i.e. somewhat lower than implied by previous models. In the present framework, the bolometric luminosity of the galaxy is expected to decrease by a factor $\text{gsim}30$ during the subsequent evolution.