A CONDITIONAL LUMINOSITY FUNCTION MODEL OF THE COSMIC FAR-INFRARED BACKGROUND ANISOTROPY POWER SPECTRUM

The cosmic far-infrared background (CFIRB) is expected to be generated by faint, dusty star-forming galaxies during the peak epoch of galaxy formation. The anisotropy power spectrum of the CFIRB captures the spatial distribution of these galaxies in dark matter halos and the spatial distribution of dark matter halos in the large-scale structure. Existing halo models of CFIRB anisotropy power spectrum either are incomplete or lead to halo model parameters that are inconsistent with the galaxy distribution selected at other wavelengths. Here, we present a conditional luminosity function approach to describe the far-IR bright galaxies. We model the 250 mu m luminosity function and its evolution with redshift and model-fit the CFIRB power spectrum at 250 mu m measured by the Herschel Space Observatory. We introduce a redshift-dependent duty cycle parameter so that we are able to estimate the typical duration of the dusty star formation process in the dark matter halos as a function of redshifts. We find that the duty cycle of galaxies contributing to the far-IR background is 0.3-0.5 with a dusty star formation phase lasting for similar to 0.3-1.6 Gyr. This result confirms the general expectation that the far-IR background is dominated by star-forming galaxies in an extended phase, not bright starbursts that are driven by galaxy mergers and last similar to 10-100 Myr. The halo occupation number for satellite galaxies has a power-law slope that is close to unity over 0 < z < 4. We find that the minimum halo mass for dusty, star-forming galaxies with L-250 > 10(10) L-circle dot is 2 x 10(11) M-circle dot and 3 x 10(10) M-circle dot at z = 1 and 2, respectively. Integrating over the galaxy population with L-250 > 10(9) L-circle dot, we find that the cosmic density of dust residing in the dusty, star-forming galaxies is responsible for the background anisotropies Omega(dust) similar to 3 x 10(-6) to 2 x 10(-5), relative to the critical density of the universe.