Dust in the Average Galaxy: Attenuation, Emission, and Opacity from 0 < Z < 7

We present constraints on the dust emission and attenuation properties of galaxies across 0<z<7 using JWST imaging from the COSMOS-Web Survey combined with deep far-infrared (FIR) and (sub)millimeter data from Spitzer, Herschel, SCUBA-2, NIKA2 and ALMA. We analyze over 500,000 galaxies to independently constrain attenuation as inferred in the rest-frame ultraviolet (UV) and optical as well as dust emission from stacked FIR spectral energy distributions (SEDs), enabling a direct comparison between the two. We find UV/optical attenuation systematically underpredicts IR luminosity by a factor of ∼3× at 0.5 < z < 7 and up to an order of magnitude for M⋆ > 1010.5 M⊙. We derive empirical relationships for the effective attenuation (AUV and AV), dust temperature, fraction of star formation that is unobscured, and dust-to-stellar mass ratio as functions of redshift and stellar mass. On galaxy-integrated scales, we separate the first order effect of star/dust geometry from dust grain properties by combining constraints on the IR SED, the UV SED, and the dust mass surface density. Importantly, we measure over an order of magnitude decrease in κUV/κFIR— the ratio of dust mass absorption coefficients in the UV at 1600˚A and FIR at 500μm — from z ∼ 0 to z ∼ 7. A depressed κUV/κFIR ratio is consistent with a deficit of small dust grains, possibly attributable to the intense radiation fields of high-z star formation; indeed, we find a redshift-invariant inverse relationship between κUV/κFIR and ΣSFR. Assuming the varying dust opacity is dominated by changes to small grains and not large grains, we infer a modest evolution in the dust-to-stellar mass ratio ∝ (1+z)^1.36 with secondary stellar mass dependence, ∝ M_⋆^−0.3. Most evolution in the dust-to-stellar ratio is at z < 1, the product of mild downward evolution in the dust-to-gas ratio combined with steep evolution in the gas-to-stellar ratio. The significant evolution and dynamic range of κUV/κFIR and prevailing disconnect between the UV/optical and FIR regimes emphasize that direct dust constraints are irreplaceable for the majority of star-forming galaxies at z < 7, not just the most extreme starformers.