Colours and luminosities of z=0.1 simulated galaxies in the EAGLE simulations

TL;DR

This study uses the EAGLE simulations and population synthesis models to analyze galaxy colours and luminosities at z=0.1, finding broad agreement with observed galaxy populations but noting some discrepancies in luminosity and colour distributions.

Contribution

It introduces a detailed dust obscuration model in EAGLE galaxy simulations and compares simulated galaxy colours and luminosities with observations, highlighting areas of agreement and discrepancy.

Findings

EAGLE reproduces the red sequence and blue cloud with correct fractions.

Simulated galaxy colours are within 0.1 magnitudes of observed values.

Discrepancies include an overextension of the blue cloud to higher luminosities.

Abstract

We calculate the colours and luminosities of redshift z = 0.1 galaxies from the EAGLE simulation suite using the GALAXEV population synthesis models. We take into account obscuration by dust in birth clouds and diffuse ISM using a two-component screen model, following the prescription of Charlot and Fall. We compare models in which the dust optical depth is constant to models where it depends on gas metallicity, gas fraction and orientation. The colours of EAGLE galaxies for the more sophisticated models are in broad agreement with those of observed galaxies. In particular, EAGLE produces a red sequence of passive galaxies and a blue cloud of star forming galaxies, with approximately the correct fraction of galaxies in each population and with g-r colours within 0.1 magnitudes of those observed. Luminosity functions from UV to NIR wavelengths differ from observations at a level comparable to systematic shifts resulting from a choice between Petrosian and Kron photometric apertures. Despite the generally good agreement there are clear discrepancies with observations. The blue cloud of EAGLE galaxies extends to somewhat higher luminosities than in the data, consistent with the modest underestimate of the passive fraction in massive EAGLE galaxies. There is also a moderate excess of bright blue galaxies compared to observations. The overall level of agreement with the observed colour distribution suggests that EAGLE galaxies at z = 0.1 have ages, metallicities and levels of obscuration that are comparable to those of observed galaxies.