Constraining the physics of star formation from CIB-cosmic shear cross-correlations

Understanding the physics of star formation is one of the key problems facing modern astrophysics. The Cosmic Infrared Background (CIB), sourced by the emission from all dusty star-forming galaxies since the epoch of reionisation, is a complementary probe to study the star formation history, as well as an important extragalactic foreground for studies of the Cosmic Microwave Background (CMB). Understanding the physics of the CIB is therefore of high importance for both cosmology and galaxy formation studies. In this paper, we make high signal-to-noise measurements of the cross-correlation between maps of the CIB from the Planck experiment, and cosmic shear measurements from the Dark Energy Survey and Kilo-Degree Survey. Cosmic shear, sourced mainly by the weak gravitational lensing of photons emitted by background galaxies, is a direct tracer of the matter distribution, and thus we can use its cross-correlation with the CIB to directly test our understanding of the link between the star formation rate (SFR) density and the matter density. We use our measurements to place constraints on a halo-based model of the SFR that parametrises the efficiency with which gas is transformed into stars as a function of halo mass and redshift. These constraints are enhanced by combining our data with model-independent measurements of the bias-weighted SFR density extracted from the tomographic cross-correlation of galaxies and the CIB. We are able to place constraints on the peak efficiency at low redshifts, $\eta=0.445^{+0.055}_{-0.11}$, and on the halo mass at which this peak efficiency is achieved today $\log_{10}(M_1/M_\odot) = 12.17\pm0.25$. Our constraints are in excellent agreement with direct measurements of the SFR density, as well as other CIB-based studies.