  We investigate the dust energy balance for the edge-on galaxy IC 2531, one of
the seven galaxies in the HEROES sample. We perform a state-of-the-art
radiative transfer modelling based, for the first time, on a set of optical and
near-infrared galaxy images. We show that taking into account near-infrared
imaging in the modelling significantly improves the constraints on the
retrieved parameters of the dust content. We confirm the result from previous
studies that including a young stellar population in the modelling is important
for explaining the observed stellar energy distribution. However, the
discrepancy between the observed and modelled thermal emission at far-infrared
wavelengths, the so-called dust energy balance problem, is still present: the
model underestimates the observed fluxes by a factor of about two. We compare
two different dust models, and find that dust parameters and thus the spectral
energy distribution in the infrared domain are sensitive to the adopted dust
model. In general, the THEMIS model reproduces the observed emission in the
infrared wavelength domain better than the popular Zubko et al. BARE-GR-S
model. Our study of IC 2531 is a pilot case for detailed and uniform radiative
transfer modelling of the entire HEROES sample, which will shed more light on
the strength and origins of the dust energy balance problem.
