INFRARED PROPERTIES OF z=7 GALAXIES FROM COSMOLOGICAL SIMULATIONS

Three-dimensional panchromatic dust radiative transfer calculations are performed on a set of 198 galaxies of stellar masses in the range of 5 x 10(8) to 3 x 10(10) M-circle dot from a cosmological hydrodynamic simulation (resolved at 29 h(-1) pc) at z similar to 7. In a companion paper, the stellar mass and UV luminosity functions and the UV-optical and FUV-NUV colors are shown to be in good agreement with observations if a Small Magellanic Cloud type dust extinction curve is adopted. Here, we make useful predictions, self-consistently, of the infrared properties of these z similar to 7 simulated galaxies that can be confronted with upcoming ALMA data. Our findings are as follows. (1) The effective radius in the rest-frame MIPS70 mu m band is in the range of 80-400 pc proper for z = 7 galaxies with L-FIR = 10(11.3)-10(12) L-circle dot. (2) The median of the peak wavelength of the far-infrared (FIR) spectral energy distribution is in the range of 45-60 mu m, depending on the dust-to-metal ratio. (3) For star formation rate in the range of 3-100 M-circle dot yr(-1), the median FIR to bolometric luminosity ratio is 60%-90%. (4) The FIR luminosity function displays a power law in the high end with a slope of -3.1 +/- 0.4 instead of the usual exponential decline.