  Cosmic far-infrared background (CFIRB) probes unresolved dusty star-forming
galaxies across cosmic time and is complementary to ultraviolet and optical
observations of galaxy evolution. In this work, we interpret the observed CFIRB
anisotropies using an empirical model based on resolved galaxies in ultraviolet
and optical surveys. Our model includes stellar mass functions, star-forming
main sequence, and dust attenuation. We find that the commonly used linear
Kennicutt relation between infrared luminosity and star formation rate
overproduces the observed CFIRB amplitudes. The observed CFIRB requires that
low-mass galaxies have lower infrared luminosities than expected from the
Kennicutt relation, implying that low-mass galaxies have lower dust content and
weaker dust attenuation. Our results demonstrate that CFIRB not only provides a
stringent consistency check for galaxy evolution models but also constrains the
dust content of low-mass galaxies.
