Extragalactic Background Light Measurements and Analysis
Summary
The extragalactic background light (EBL) encompasses all accumulated radiation from ultraviolet to far-infrared wavelengths produced by stars, galaxies and the interstellar medium since the epoch of recombination. Its precise characterisation offers critical insight into the history of cosmic star formation, galaxy evolution and large-scale structure. Direct photometric approaches rely on deep galaxy counts from space- and ground-based observatories, extrapolating number-flux distributions to infer the integrated galaxy light (IGL) while carefully subtracting foregrounds such as zodiacal light and diffuse Galactic emission. Complementary indirect methods exploit the attenuation imprint on high-energy gamma-ray spectra from distant blazars, providing an EBL spectrum largely free from evolutionary assumptions. Recent all-sky surveys with the Hubble Space Telescope have refined surface-brightness modelling to sub-per cent accuracy, and intensity-mapping experiments are extending measurements into the near-infrared by mitigating instrumental noise on large angular scales. Emerging strategies include dipole analyses of the cosmic infrared background to isolate kinematic and potential non-kinematic components. Together, these advances are converging on a self-consistent picture of the optical and infrared background, constraining reionisation, the build-up of dust-obscured star formation and cosmological parameters such as H₀ in an evolving Universe.
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Extragalactic Background Light Measurements and Analysis publication trend
The graph below shows the total number of articles in extragalactic background light measurements and analysis across all publications each year (not limited to Nature Index journals).
Technical terms
Extragalactic background light (EBL): The cumulative electromagnetic radiation from all extragalactic sources since recombination, spanning ultraviolet to far-infrared wavelengths.
Integrated galaxy light (IGL): The summed contribution of resolved galaxies to the EBL, obtained by integrating galaxy number-flux distributions.
Gamma-ray attenuation imprint: The reduction in high-energy gamma-ray flux from distant sources due to pair production with EBL photons, used to infer EBL intensity.
Zodiacal light: Foreground sunlight scattered by interplanetary dust, constituting a major contaminant in direct EBL photometry.
Compton–Getting effect: A kinematic modulation of observed background intensity resulting from the observer’s motion relative to the photon rest frame, employed to measure dipole anisotropies.
References
- MEASUREMENTS OF EXTRAGALACTIC BACKGROUND LIGHT FROM THE FAR UV TO THE FAR IR FROM DEEP GROUND- AND SPACE-BASED GALAXY COUNTS. The Astrophysical Journal (2016).
- The Cosmological Optical Convergence: Extragalactic Background Light from TeV Gamma Rays. The Astrophysical Journal Letters (2024).
- SKYSURF-4: Panchromatic Hubble Space Telescope All-Sky Surface-brightness Measurement Methods and Results. The Astronomical Journal (2023).
- Noise Reduction Methods for Large-scale Intensity-mapping Measurements with Infrared Detector Arrays. The Astrophysical Journal Supplement Series (2023).
- A Measurement of the Cosmic Optical Background and Diffuse Galactic Light Scaling from the R. The Astrophysical Journal (2023).
- Euclid preparation. Astronomy & Astrophysics (2024).
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