The evolution of the UV-to-mm extragalactic background light: evidence for a top-heavy initial mass function?
We present predictions for the UV-to-mm extragalactic background light (EBL) from a recent version of the GALFORM semi-analytical model of galaxy formation which invokes a top-heavy stellar initial mass function (IMF) for galaxies undergoing dynamically triggered bursts of star formation. We combine GALFORM with the GRASIL radiative transfer code for computing fully self-consistent UV-to-mm spectral energy distributions for each simulated galaxy, accounting for the absorption and re-emission of stellar radiation by interstellar dust. The predicted EBL is in near-perfect agreement with recent observations over the whole UV-to-mm spectrum, as is the evolution of the cosmic spectral energy distribution over the redshift range for which observations are available (z ≲ 1). We show that approximately 90 per cent of the EBL is produced at z < 2 although this shifts to higher redshifts for sub-mm wavelengths. We assess whether the top-heavy IMF in starbursts is necessary in order to reproduce the EBL at the same time as other key observables, and find that variant models with a universal solar-neighbourhood IMF display poorer agreement with EBL observations over the whole UV-to-mm spectrum and fail to match the counts of galaxies in the sub-mm.
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 2019
- galaxies: evolution;
- galaxies: formation;
- infrared: galaxies;
- submillimetre: galaxies;
- ultraviolet: galaxies;
- Astrophysics - Astrophysics of Galaxies
- 15 pages (+6 of Appendices), 9 figures (+5 in Appendices), Main results in Figs. 1 and 6. Accepted for publication in MNRAS