Luminosity Density of Galaxies and Cosmic Star Formation Rate from Λ Cold Dark Matter Hydrodynamical Simulations

We compute the cosmic star formation rate (SFR) and the rest-frame comovingluminosity density in various pass-bands as a function of redshift usinglarge-scale \Lambda-CDM hydrodynamical simulations with the aim ofunderstanding their behavior as a function of redshift. To calculate theluminosity density of galaxies, we use an updated isochrone synthesis modelwhich takes metallicity variations into account. The computed SFR and theUV-luminosity density have a steep rise from z=0 to 1, a moderate plateaubetween z=1 - 3, and a gradual decrease beyond z=3. The raw calculated resultsare significantly above the observed luminosity density, which can be explainedeither by dust extinction or the possibly inappropriate input parameters of thesimulation. We model the dust extinction by introducing a parameter f; thefraction of the total stellar luminosity (not galaxy population) that isheavily obscured and thus only appears in the far-infrared to sub-millimeterwavelength range. When we correct our input parameters, and apply dustextinction with f=0.65, the resulting luminosity density fits variousobservations reasonably well, including the present stellar mass density, thelocal B-band galaxy luminosity density, and the FIR-to-submm extragalacticbackground. Our result is consistent with the picture that \sim 2/3 of thetotal stellar emission is heavily obscured by dust and observed only in theFIR. The rest of the emission is only moderately obscured which can be observedin the optical to near-IR wavelength range. We also argue that the steepfalloff of the SFR from z=1 to 0 is partly due to the shock-heating of theuniverse at late times, which produces gas which is too hot to easily condenseinto star-forming regions.Comment: 25 pages, 6 figures. Accepted version in ApJ. Substantially revised from the previous version. More emphasis on the comparison with various observations and the hidden star formation by dust extinctio