  Utilizing state-of-the-art, adaptive mesh-refinement cosmological
hydrodynamic simulations with ultra-high resolution (114h-1pc) and large sample
size (>3300 galaxies of stellar mass >10^9Msun), we show how the stellar light
of Lyman Break Galaxies at z=2 is distributed between optical/ultra-violet (UV)
and far-infrared (FIR) bands. With a single scalar parameter for dust
obscuration we can simultaneously reproduce the observed UV luminosity function
for the entire range (3-100 Msun/yr) and extant FIR luminosity function at the
bright end (>20Msun/yr). We quantify that galaxies more massive or having
higher SFR tend to have larger amounts of dust obscuration mostly due to a
trend in column density and in a minor part due to a mass (or SFR)-metallicity
relation. It is predicted that the FIR luminosity function in the range
SFR=1-100Msun/yr is a powerlaw with a slope about -1.7. We further predict that
there is a "galaxy desert" at SFR(FIR) < 0.02 (SFR(UV)/10Msun/yr)^2.1 Msun/yr
in the SFR(UV)-SFR(FIR) plane. Detailed distributions of SFR(FIR) at a fixed
SFR(UV) are presented. Upcoming observations by ALMA should test this model. If
confirmed, it validates the predictions of the standard cold dark matter model
and has important implications on the intrinsic SFR function of galaxies at
high redshift.
