Models for infrared and submillimetre counts and backgrounds

Abstract

A simple and versatile parameterized approach to the star formation history allows a quantitative investigation of the constraints from far infrared and submillimetre counts and background intensity measurements. The models include four spectral components: infrared cirrus, an M82-like starburst, an Arp220-like starburst and an AGN dust torus. The 60 $μ$m luminosity function is determined for each chosen rate of evolution using the PSCz redshift data for 15000 galaxies. The proportions of each spectral type as a function of 60 $μ$m luminosity are chosen for consistency with IRAS and SCUBA colour-luminosity relations, and with the fraction of AGN as a function of luminosity found in 12 $μ$m samples. A good fit to the observed counts at 0.44, 2.2, 15, 60, 90, 175 and 850 $μ$m can be found with pure luminosity evolution in all 3 cosmological models investigated: $Ω_o$ = 1, $Ω_o$ = 0.3 ($Λ$ = 0), and $Ω_o$ = 0.3, $Λ$ = 0.7. All 3 models also give an acceptable fit to the integrated background spectrum. The total mass-density of stars generated is consistent with that observed, in all 3 cosmological models.