Abstract
DISTANT radio galaxies provide valuable insights into the properties of the young Universe—they are the only known extended optical sources at high redshift and might represent an early stage in the formation and evolution of galaxies in general. This extended optical emission often has very complex morphologies, but the origin of the light is still unclear. Here we report spectroscopic observations for several distant radio galaxies (0.75≤ z ≤ 1.1) in which the rest-frame spectra exhibit featureless continua between 2,500 Å and 5,000 Å. We see no evidence for the break in the spectrum at 4,000 Å expected for an old stellar population1–3, and suggest that young stars or scattered emissions from the active nuclei are responsible for most of the observed light. In either case, this implies that the source of the optical emission is com-parable in age to the associated radio source, namely 107 years or less.
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Hammer, F., Fèvre, O. & Angonin, M. A young source of optical emission from distant radio galaxies. Nature 362, 324–326 (1993). https://doi.org/10.1038/362324a0
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DOI: https://doi.org/10.1038/362324a0
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