Extragalactic Background Light

Extragalactic Background Light
Name	Extragalactic Background Light
Epoch	Cosmic
Components	Infrared, optical, ultraviolet, microwave, X-ray
Discovered	1960s
Major contributors	Galaxies, Active Galactic Nuclei, Star formation, Dust emission

Extragalactic Background Light The Extragalactic Background Light is the integrated diffuse radiation from all extragalactic sources across cosmic history, observed primarily at ultraviolet, optical, and infrared wavelengths. It connects empirical programs such as the Hubble Space Telescope deep fields, the Spitzer Space Telescope surveys, and the Planck cosmological analyses, while informing theoretical frameworks developed by groups at institutions like the Institute for Advanced Study, Max Planck Institute for Astrophysics, and Princeton University.

Introduction

The background arises as an all-sky irradiance produced by cumulative emission from objects studied in campaigns by the Sloan Digital Sky Survey, the Two Micron All Sky Survey, and the Chandra X-ray Observatory, and it is central to debates in forums including the American Astronomical Society meetings and workshops at the Kavli Institute for Theoretical Physics. Measurements intersect programs led by investigators at NASA, the European Space Agency, and observatories such as the Very Large Telescope and Keck Observatory. The quantity informs landmark theoretical constructs from teams associated with the Harvard–Smithsonian Center for Astrophysics, the University of Cambridge, and the California Institute of Technology.

Composition and Spectral Properties

The spectrum comprises ultraviolet emission traced by surveys from the Galaxy Evolution Explorer, optical light characterized by the deepest exposures from the Hubble Deep Field and Hubble Ultra Deep Field, and infrared components measured by the Infrared Astronomical Satellite, AKARI, and Herschel Space Observatory, with energy redistributed by dust heating studied in projects at the Max Planck Institute for Extraterrestrial Physics and Jet Propulsion Laboratory. High-energy tails overlap with observations from the Fermi Gamma-ray Space Telescope and the International Gamma-Ray Astrophysics Laboratory, linking to attenuation signatures in spectra of sources catalogued by the VERITAS and MAGIC collaborations. The spectrum shows peaks tied to stellar population synthesis models developed by research groups at Rutgers University, University of Oxford, and Columbia University, and features influenced by metallicity studies from the European Southern Observatory programs.

Sources and Origins

Primary contributors include integrated starlight from galaxies catalogued by the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey, dusty star-forming galaxies identified by the Atacama Large Millimeter/submillimeter Array, and accretion-related emission from active nuclei in catalogs maintained by the Sloan Digital Sky Survey and the ROSAT mission. Early-universe sources invoke populations studied in surveys by the James Webb Space Telescope teams and theoretical proposals developed at Harvard University and Yale University about contributions from Population III stars, while black hole growth scenarios feature in models from the Kavli Institute and the Max Planck Society. Contributions from diffuse intrahalo light are analyzed in projects led by investigators at University of Chicago and Princeton University, and reionization-era signals connect to results from the Wilkinson Microwave Anisotropy Probe and Planck collaborations.

Measurement Techniques and Observational Challenges

Direct photometric measurements use instruments aboard COBE, Spitzer Space Telescope, Herschel Space Observatory, and ground-based telescopes such as Subaru Telescope and Gemini Observatory, with calibration efforts coordinated through teams at National Aeronautics and Space Administration facilities and the European Southern Observatory. Indirect constraints derive from gamma-ray attenuation studies of blazars observed by Fermi Gamma-ray Space Telescope, H.E.S.S., and VERITAS, and from cross-correlation analyses between catalogs like the Sloan Digital Sky Survey and maps from Planck. Foreground subtraction requires modeling zodiacal light informed by measurements from Pioneer 10 and Ulysses, and Galactic cirrus corrections implemented using datasets from the Infrared Astronomical Satellite and the Wide-field Infrared Survey Explorer. Systematic uncertainties are debated in working groups at the International Astronomical Union and in collaborations including the European Space Agency science teams.

Cosmological and Astrophysical Implications

The light encodes the integrated star-formation history constrained by comparisons to the Madau–Dickinson star formation rate compilations and to simulations from the Illustris and EAGLE projects, and it impacts propagation of very high-energy photons in studies performed by the Fermi Gamma-ray Space Telescope and the High Energy Stereoscopic System. Constraints on dark-matter annihilation scenarios and on exotic energy injection have been explored by theorists at CERN, Perimeter Institute, and SLAC National Accelerator Laboratory, while implications for galaxy formation and feedback processes are central to research at the Max Planck Institute for Astronomy and the Space Telescope Science Institute. Measurements inform cosmological parameter estimation alongside results from Planck, Wilkinson Microwave Anisotropy Probe, and large-scale structure surveys like the Dark Energy Survey.

Modeling and Theoretical Interpretations

Semi-analytic models constructed by teams at Stanford University and University College London combine stellar population synthesis codes from the Padova group and dust models calibrated against observations from Herschel Space Observatory and Spitzer Space Telescope. Radiative transfer implementations used in projects at Max Planck Institute for Astrophysics and Princeton University connect to hydrodynamical simulations run by the Illustris and EAGLE consortia, and analytic approaches link to formation histories studied at Caltech and University of California, Berkeley. Ongoing theoretical debates occur in seminars at the Institute for Advanced Study and workshops organized by the Kavli Foundation, where interpretations balance empirical constraints from missions such as Hubble Space Telescope, James Webb Space Telescope, and Fermi Gamma-ray Space Telescope.

Category:Cosmology