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Scattering And Absorption of Light in Planetary Regoliths
Published on: July 1, 2019
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The diffuse γ-ray background is dominated by star-forming galaxies.
Matt A Roth1, Mark R Krumholz2,3, Roland M Crocker2
1Research School of Astronomy and Astrophysics, The Australian National University, Canberra, Australian Capital Territory, Australia. matt.roth@anu.edu.au.
Nature
|September 16, 2021
Summary
Star-forming galaxies alone explain the diffuse gamma-ray background. A new physical model accurately predicts gamma-ray emission from cosmic ray interactions in galaxies, matching Fermi telescope observations.
Area of Science:
- Astrophysics
- Cosmic Ray Physics
- Galactic Astronomy
Background:
- The Fermi Gamma-ray Space Telescope detected a diffuse gamma-ray background.
- Previous models struggled to constrain contributions from active galactic nuclei and star-forming galaxies.
Purpose of the Study:
- To develop a physical model for gamma-ray emission from star-forming galaxies.
- To determine if star-forming galaxies can fully account for the isotropic gamma-ray background.
Main Methods:
- Developed a physical model for gamma-ray emission from cosmic ray interactions with the interstellar medium.
- Validated the model against local galaxy observations.
- Applied the model to the cosmological star-forming galaxy population.
Main Results:
- The physical model accurately matches the intensity and spectral slope of the observed gamma-ray background.
- Star-forming galaxies alone can explain the full diffuse, isotropic gamma-ray background.
- The model does not rely on empirical scalings.
Conclusions:
- Star-forming galaxies are the primary contributors to the diffuse extragalactic gamma-ray background.
- This study provides a robust physical explanation for the observed gamma-ray background.
- The findings resolve a long-standing question in high-energy astrophysics.
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