Panchromatic Spectral Energy Distributions of simulated galaxies: results at redshift $z=0$

TL;DR

This paper predicts the spectral energy distributions of simulated galaxies at redshift zero, comparing them with observations and analyzing correlations with galaxy properties to understand dust heating and selection biases.

Contribution

It introduces a method combining N-body+hydro simulations with radiative transfer to produce realistic galaxy SEDs at z=0, and analyzes their properties and correlations.

Findings

Simulated galaxy SEDs resemble observed ones when normalized at 3.6 μm.

IR luminosity correlates best with SFR up to 160 μm, then with molecular and dust mass.

Cold dust heating is mainly driven by SFR, with stellar mass playing a minor role.

Abstract

We present predictions of Spectral Energy Distributions (SEDs), from the UV to the FIR, of simulated galaxies at $z=0$. These were obtained by post-processing the results of an N-body+hydro simulation of a small cosmological volume, that uses the Multi-Phase Particle Integrator (MUPPI) for star formation and stellar feedback, with the GRASIL-3D radiative transfer code, that includes reprocessing of UV light by dust. Physical properties of galaxies resemble observed ones, though with some tension at small and large stellar masses. Comparing predicted SEDs of simulated galaxies with different samples of local galaxies, we find that these resemble observed ones, when normalised at 3.6 $\mu$m. A comparison with the Herschel Reference Survey shows that, when binning galaxies in Star Formation Rate (SFR), average SEDs are reproduced to within a factor of $\sim2$ even in normalization, while binning in stellar mass highlights the same tension that is present in the stellar mass -- SFR plane. We use our sample to investigate the correlation of IR luminosity in Spitzer and Herschel bands with several galaxy properties. SFR is the quantity that best correlates with IR light up to $160\ \mu$m, while at longer wavelengths better correlations are found with molecular mass and, at $500\ \mu$m, with dust mass. However, using the position of the FIR peak as a proxy for cold dust temperature, we assess that heating of cold dust is mostly determined by SFR, with stellar mass giving only a minor contribution. We finally show how our sample of simulated galaxies can be used as a guide to understand the physical properties and selection biases of observed samples.