Orateur
Description
Rotational lines of carbon monoxide (CO) emitted by star-forming galaxies are redshifted into the frequency bands of CMB experiments. Because these bands are broad, many transitions emitted over a wide redshift range add up to a continuum-like signal that is strongly correlated with the cosmic infrared background (CIB). Current predictions of this foreground rely mostly on simulations. I will present an analytic, full-shape halo model for the CO auto-spectrum and the CO×CIB cross-spectrum in CMB bands. It has separate occupation distributions for CO and infrared emitters, includes central and satellite galaxies and CO transitions up to J = 13, and covers all frequency combinations. CO and infrared luminosities derive from the same star formation rate. At ℓ = 3000, the CO×CIB contribution reaches 0.6 and 1.6 µK² at 150 and 220 GHz, comparable to the kSZ power. The star formation history and CO excitation dominate the modelling uncertainty. Fisher forecasts show that, for an ACT-like experiment, neglecting CO biases the radio and SZ foreground parameters by 1–2.5σ while leaving cosmology unaffected. For a CMB-HD-like experiment, CO is detected at high significance, and ignoring it biases cosmological parameters by up to ~2σ. CO should therefore be part of the foreground model of future high-resolution CMB analyses.