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

Abstract

We present constraints on the dust emission and attenuation properties of galaxies across 0&lt;z&lt;7 using JWST imaging from the COSMOS-Web Survey combined with deep FIR/(sub)millimeter data from Spitzer, Herschel, SCUBA-2, NIKA-2 and ALMA. We analyze over 500,000 galaxies to independently constrain attenuation 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 ~3x at 0.5&lt;z&lt;7 and up to an order of magnitude for <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⋆</mml:mo> </mml:msub> <mml:mo>&gt;</mml:mo> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>10.5</mml:mn> </mml:msup> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⊙</mml:mo> </mml:msub> </mml:mrow> </mml:math> . We derive empirical relationships for the effective attenuation, dust temperature, fraction of star formation that is unobscured, and dust-to-stellar mass ratio as functions of redshift and stellar mass. We separate the first order effect of star/dust geometry from dust grain properties by combining constraints on the IR SED, UV SED, and dust mass surface density. Importantly, we measure over an order of magnitude decrease in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msub> <mml:mi>κ</mml:mi> <mml:mrow> <mml:mi>U</mml:mi> <mml:mi>V</mml:mi> </mml:mrow> </mml:msub> <mml:mi>/</mml:mi> <mml:msub> <mml:mi>κ</mml:mi> <mml:mrow> <mml:mi>F</mml:mi> <mml:mi>I</mml:mi> <mml:mi>R</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> –the ratio of dust mass absorption coefficients in the UV at 1600Å and FIR at 500 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>μ</mml:mi> </mml:math> m–from z~0 to z~7. A depressed <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msub> <mml:mi>κ</mml:mi> <mml:mrow> <mml:mi>U</mml:mi> <mml:mi>V</mml:mi> </mml:mrow> </mml:msub> <mml:mi>/</mml:mi> <mml:msub> <mml:mi>κ</mml:mi> <mml:mrow> <mml:mi>F</mml:mi> <mml:mi>I</mml:mi> <mml:mi>R</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> is consistent with a deficit of small dust grains, possibly attributable to the intense radiation fields of high- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>z</mml:mi> </mml:math> star formation; indeed, we find a redshift-invariant inverse relationship between <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msub> <mml:mi>κ</mml:mi> <mml:mrow> <mml:mi>U</mml:mi> <mml:mi>V</mml:mi> </mml:mrow> </mml:msub> <mml:mi>/</mml:mi> <mml:msub> <mml:mi>κ</mml:mi> <mml:mrow> <mml:mi>F</mml:mi> <mml:mi>I</mml:mi> <mml:mi>R</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msub> <mml:mi>Σ</mml:mi> <mml:mrow> <mml:mi>S</mml:mi> <mml:mi>F</mml:mi> <mml:mi>R</mml:mi> </mml:mrow> </mml:msub> </mml:math> . Most evolution in the dust-to-stellar ratio is at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>z</mml:mi> <mml:mo>&lt;</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:math> , 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:msub> <mml:mi>κ</mml:mi> <mml:mrow> <mml:mi>U</mml:mi> <mml:mi>V</mml:mi> </mml:mrow> </mml:msub> <mml:mi>/</mml:mi> <mml:msub> <mml:mi>κ</mml:mi> <mml:mrow> <mml:mi>F</mml:mi> <mml:mi>I</mml:mi> <mml:mi>R</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mi>z</mml:mi> <mml:mo>&lt;</mml:mo> <mml:mn>7</mml:mn> </mml:mrow> </mml:math> , not just the most extreme star-formers.