Extragalactic Background Light: Measurements and Applications

Abstract

This review covers the measurements related to the extragalactic background light (EBL) intensity from gamma-rays to radio in the electromagnetic spectrum over 20 decades in the wavelength. The cosmic microwave background (CMB) remains the best measured spectrum with an accuracy better than 1%. The measurements related to the cosmic optical background (COB), centered at 1 microns, are impacted by the large zodiacal light associated with interplanetary dust in the inner Solar system. The best measurements of COB come from an indirect technique involving Gamma-ray spectra of bright blazars with an absorption feature resulting from pair-production off of COB photons. The cosmic infrared background (CIB) peaking at around 100 microns established an energetically important background with an intensity comparable to the optical background. This discovery paved the path for large aperture far-infrared and sub-millimeter observations resulting in the discovery of dusty, starbursting galaxies. Their role in galaxy formation and evolution remains an active area of research in modern-day astrophysics. The extreme UV background remains mostly unexplored and will be a challenge to measure due to the high Galactic background and absorption of extragalactic photons by the intergalactic medium at these EUV/soft X-ray energies. We also summarize our understanding of the spatial anisotropies and angular power spectra of intensity fluctuations. We motivate a precise direct measurement of the COB between 0.1 to 5 microns using a small aperture telescope observing either from the outer Solar system, at distances of 5 AU or more, or out of the ecliptic plane. Other future applications include improving our understanding of the background at TeV energies and spectral distortions of CMB and CIB.

24 pages, 3 figures; invited review for Royal Society Open Science (RSOS), see http://rsos.royalsocietypublishing.org. Electronic files and data related to Figure 1 are available at http://herschel.uci.edu

References in corpus (21)

• The synthesis of the cosmic X-ray background in the Chandra and XMM-Newton era
• The Cosmic Infrared Background Resolved by Spitzer. Contributions of Mid-Infrared Galaxies to the Far-Infrared Background
• Strong support for the millisecond pulsar origin of the Galactic center GeV excess
• The Global 21 Centimeter Background from High Redshifts
• Search for Gamma-Ray Emission from DES Dwarf Spheroidal Galaxy Candidates with Fermi-LAT Data
• INTEGRAL observations of the cosmic X-ray background in the 5-100 keV range via occultation by the Earth
• Cosmology with the SPHEREX All-Sky Spectral Survey
• Indication of Gamma-ray Emission from the Newly Discovered Dwarf Galaxy Reticulum II
• Gamma Ray Spectrum from Gravitino Dark Matter Decay
• The nature of the Diffuse Gamma-Ray Background
• On the Origin of Near-Infrared Extragalactic Background Light Anisotropy
• Correlated Anisotropies in the Cosmic Far-Infrared Background Detected by MIPS/Spitzer: Constraint on the Bias
• Constraints on decaying dark matter from the extragalactic gamma-ray background
• Resolving the Origin of the Diffuse Soft X-ray Background
• Young Pulsars and the Galactic Center GeV Gamma-ray Excess
• The 1 um discontinuity in the Extragalactic Background Light spectrum: an artefact of foreground subtraction
• Anisotropy Studies of the Unresolved Far-infrared Background
• Diffuse Extragalactic Background Radiation
• Clustering of the IR Background Light with Spitzer: Contribution from Resolved Sources
• HerMES: Current Cosmic Infrared Background Estimates Can be Explained by Known Galaxies and their Faint Companions at z < 4
• Science with CMB spectral distortions

Cited by in corpus (1)

• Quantum gravity phenomenology at the dawn of the multi-messenger era -- A review