The Energy Output of the Universe from 0.1 to 1000 microns

Authors: Simon P. Driver, Cristina C. Popescu, Richard J. Tuffs, Alister W. Graham, Jochen Liske, Ivan Baldry

Abstract: The dominant source of electromagnetic energy in the Universe today (over ultraviolet, optical and near-infrared wavelengths) is starlight. However, quantifying the amount of starlight produced has proven difficult due to interstellar dust grains which attenuate some unknown fraction of the light. Combining a recently calibrated galactic dust model with observations of 10,000 nearby galaxies we find that (integrated over all galaxy types and orientations) only (11±2)% of the 0.1 micron photons escape their host galaxies; this value rises linearly with the logarithm of the wavelength to (87±3)% at 2.1 microns. We deduce that the energy output from stars in the nearby Universe is (1.6±0.2) x 1035 W Mpc-3 of which only (0.9±0.1) x 1035 W Mpc-3 escapes directly into the inter-galactic medium. Some further ramifications of dust attenuation are discussed, and equations that correct individual galaxy flux measurements for its effect are provided.