Dust attenuation, dust content and geometry of star-forming galaxies

TL;DR

This study investigates the dust properties and geometry in star-forming galaxies across redshifts 0 to 2.5, using observational data and radiative transfer models to understand dust attenuation and distribution.

Contribution

It introduces a comprehensive analysis combining observational datasets with radiative transfer models to infer dust geometry and reconcile different dust mass estimates across redshifts.

Findings

Attenuation-based dust mass estimates conflict with far-infrared constraints at high redshift.

Clumpier dust geometries can reconcile UV-to-NIR and far-infrared observations.

Dust distribution affects observed galaxy sizes and surface brightness profiles.

Abstract

We analyse the joint distribution of dust attenuation and projected axis ratios, together with galaxy size and surface brightness profile information, to infer lessons on the dust content and star/dust geometry within star-forming galaxies at 0 < z <2.5. To do so, we make use of large observational datasets from KiDS+VIKING+HSC-SSP and extend the analysis out to redshift z = 2.5 using the HST surveys CANDELS and 3D-DASH. We construct suites of SKIRT radiative transfer models for idealized galaxies observed under random viewing angles with the aim of reproducing the aforementioned distributions, including the level and inclination dependence of dust attenuation. We find that attenuation-based dust mass estimates are at odds with constraints from far-infrared observations, especially at higher redshifts, when assuming smooth star and dust geometries of equal extent. We demonstrate that UV-to-near-IR and far-infrared constraints can be reconciled by invoking clumpier dust geometries for galaxies at higher redshifts and/or very compact dust cores. We discuss implications for the significant wavelength- and redshift-dependent differences between half-light and half-mass radii that result from spatially varying dust columns within -- especially massive -- star-forming galaxies.