Extragalactic background light

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Extragalactic background light (CUVOB) in the spectral course of the entire diffuse extragalactic background radiation

The extragalactic background light ( English extragalactic background light ; also CUVOB , i.e. Cosmic Ultraviolet / Optical Background , German cosmic ultraviolet and optical background ) is a diffuse isotropic electromagnetic radiation in the range of infrared , ultraviolet and optical radiation. It is composed of red-shifted radiation from star formation plus a small proportion of active galactic nuclei .

classification

The extragalactic background light is part of the metagalactic radiation field or the diffuse extragalactic background radiation, which comprises the entire range of electromagnetic radiation from radio to gamma radiation . Other parts of the diffuse extragalactic background radiation are:

  • the cosmic radio background ( cosmic radio background CRB )
  • the cosmic microwave background radiation ( cosmic microwave background CMB )
  • the cosmic ray background ( cosmic X-ray background CXB )
  • the diffuse extragalactic gamma radiation ( diffuse extragalactic gamma-ray radiation or cosmic gamma-ray background CGB ).

proof

A direct detection of the extragalactic background light with wavelengths of 0.1 µm to 1 mm is difficult, since the contribution of the zodiacal light and of non-resolved sources is difficult to determine. Because of these uncertainties, different values ​​for the radiation field of the CUVOB have been given in the literature. The direct detection is still limited to the optical range because of the low sensitivity of the detectors in the UV range and a low resolution in the far infrared.

In the case of a high redshift with z  > 2 in the area of ​​the Lyman alpha forest , the extragalactic background light modulates the absorption in the spectra of some quasars and blazars . The modulations make it possible to set an upper limit for the contribution of the CUVOB.

In the area of ​​high-energy gamma radiation, an interaction with the extragalactic background light has been suspected. The interaction leads to a conversion of the gamma radiation with the creation of electron - positron pairs. These highly relativistic electron-positron pairs in turn should scatter the cosmic microwave background radiation via the inverse Compton effect and generate secondary gamma radiation. A proof of this secondary gamma radiation has not yet been successful. The attenuation of the gamma radiation can be used to set upper limits on the development and amplitude of the extragalactic background light.

meaning

The extragalactic background light is part of the observational cosmology . It represents a significant part of the electromagnetic radiation released by nuclear and gravitational processes since the age of recombination . The radiation is shifted by the cosmic redshift and modified by absorption and re -emission by dust. Therefore the intensity and the spectral course of the extragalactic background light provide information about the formation and development of galaxies and their components.

literature

  • Vikram Khaire, Raghunathan Srianand: Star formation history, dust attenuation and extragalactic background light . In: Astrophysics. Solar and Stellar Astrophysics . 2014, arxiv : 1405.7038v1 .
  • Luigi Costamante: Gamma-rays from Blazars and the Extragalactic Background Light . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1309.0612v1 .
  • Yan Gong, Asantha Cooray: THE EXTRAGALACTIC BACKGROUND LIGHT FROM THE MEASUREMENTS OF THE ATTENUATION OF HIGH-ENERGY GAMMA-RAY SPECTRUM . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1305.5249v2 .
  • M. Ackermann et al .: The Imprint of The Extragalactic Background Light in the Gamma-Ray Spectra of Blazars . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1211.1671v1 .
  • Eli Dwek, Frank Krennrich: The Extragalactic Background Light and the Gamma-ray Opacity of the Universe . In: Astrophysics. Solar and Stellar Astrophysics . 2012, arxiv : 1209.4661v2 .