The many colors of the TNG100 simulation

TL;DR

This study applies advanced radiative transfer modeling to TNG100 simulated galaxies, producing realistic spectral energy distributions that closely match observations, with some discrepancies in ultraviolet colors and mid-infrared fluxes.

Contribution

It demonstrates a detailed post-processing pipeline for TNG100 galaxies using SKIRT, producing publicly available mock SEDs that enhance the simulation's observational relevance.

Findings

TNG100 reproduces low-redshift luminosity functions accurately.

Simulated galaxies show UV colors slightly too blue compared to observations.

Mid-infrared fluxes are elevated due to dust heating effects.

Abstract

We apply the 3D dust radiative transfer code SKIRT to the low-redshift ($z\leq0.1$) galaxy population in the TNG100 cosmological simulation, the fiducial run of the IllustrisTNG project. We compute global fluxes and spectral energy distributions (SEDs) from the far-ultraviolet to the sub-millimeter for $\approx\,$60 000 galaxies. Our post-processing methodology follows the study of Tr\v{c}ka et al. (2022) of the higher-resolution TNG50 simulation. We verify that TNG100 reproduces observational luminosity functions at low redshifts to excellent precision, unlike TNG50. Additionally, we test the realism of our TNG100 plus SKIRT fluxes by comparing various flux and color relations to data from the GAMA survey. TNG100 broadly reproduces the observed distributions, but we predict ultraviolet colors that are too blue by $\approx\,$0.4 mag, possibly related to the extinction in the star-forming regions subgrid model not being selective enough. Furthermore, we find that the simulated galaxies exhibit mid-infrared fluxes elevated by up to $\approx\,$0.5 mag that we attribute to overly effective stochastic heating of the diffuse dust. All synthetic broadband fluxes and SEDs are made publicly available in three orientations and four apertures, and can readily be used to study TNG100 galaxies in a mock observational fashion.