Exploring galaxy evolution from infrared number counts and cosmic infraredbackground

Recently reported infrared (IR) galaxy number counts and cosmic infrared ba ckground (CIRB) all suggest that galaxies have experienced strong evolution sometime in their lifetime. We statistically estimate the galaxy evolution history from these data. We find that an order-of-magnitude increase of th e far-infrared (FIR) luminosity at redshift z = 0.5-1.0 is necessary to rep roduce the very high CIRB intensity at 140 mum reported by Hauser et al. (1 998, AAA 070.161.559) and decreases to, even at most, a factor of 10 toward z similar to 5, though many variants are allowed within these constraints. This evolution history also satisfies the constraints from the galaxy numb er counts obtained by IRAS, ISO and, roughly, SCUBA, The rapid evolution of the comoving IR luminosity density required from the CIRB well reproduces the very steep slope of galaxy number counts obtained by ISO. We also estim ate the cosmic star formation history (SFH) from the obtained FIR luminosit y density, considering the effect of the metal enrichment in galaxies. The derived SFH increases steeply with redshift in 0 < z < 0.75, and becomes fl at or even declines at z > 0.75. This is consistent with the SFH estimated from the reported ultraviolet luminosity density. In addition, we present t he performance of the Japanese ASTRO-F FIR galaxy survey. We show the expec ted number counts in the survey. We also evaluate how large a sky area is n ecessary to derive secure information of galaxy evolution up to z similar t o 1 from the survey, and find that at least 50-300 deg(2) is required.