Uncovering the truth about M101, NGC 3938, and their significant others through radiative transfer

TL;DR

This study uses radiative transfer models to decode the distribution of dust, gas, and stars in nearby face-on galaxies, providing insights into their physical properties and structural relations, with implications for understanding galaxy evolution.

Contribution

The paper introduces a radiative transfer modeling approach applied to multiple galaxies, confirming the consistency of Milky Way-type dust properties and revealing a structural relation in star formation and stellar mass densities.

Findings

Milky Way-type dust fits observed data well.

No evidence of submm excess or modified dust properties.

Discovered a steeper structural relation in SFR vs. stellar mass surface density.

Abstract

Solving the inverse problem in spiral galaxies, that allows the derivation of the spatial distribution of dust, gas and stars, together with their associated physical properties, directly from panchromatic imaging observations, is one of the main goals of this work. To this end we used radiative transfer models to decode the spatial and spectral distribution of the nearby face-on galaxies M101 and NGC 3938. In both cases we provide excellent fits to the surface-brightness distributions derived from GALEX, SDSS, 2MASS, Spitzer and Herschel imaging observations. Together with previous results from M33, NGC 628, M51 and the Milky Way, we obtain a small statistical sample of modelled nearby galaxies that we analyse in this work. We find that in all cases Milky Way-type dust with Draine-like optical properties provide consistent and successful solutions. We do not find any "submm excess", and no need for modified dust-grain properties. Intrinsic fundamental quantities like star-formation rates (SFR), specific SFR (sSFR), dust opacities and attenuations are derived as a function of position in the galaxy and overall trends are discussed. In the SFR surface density versus stellar mass surface density space we find a structurally resolved relation (SRR) for the morphological components of our galaxies, that is steeper than the main sequence (MS). Exception to this is for NGC 628, where the SRR is parallel to the MS.