Fermi LAT measurements of diffuse γ-ray emission: results at the first-year milestone
Abstract
For more than one year the Fermi Large Area Telescope has been surveying the γ-ray sky from 20 MeV to more than 300 GeV with unprecedented statistics and angular resolution. One of the key science targets of the Fermi mission is diffuse γ-ray emission. Galactic interstellar γ-ray emission is produced by interactions of high-energy cosmic rays with the interstellar gas and radiation field. We review the most important results on the subject obtained so far: the non-confirmation of the excess of diffuse GeV emission seen by EGRET, the measurement of the γ-ray emissivity spectrum of local interstellar gas, the study of the gradient of cosmic-ray densities and of the XCO = N(H2)/WCO ratio in the outer Galaxy. We also catch a glimpse at diffuse γ-ray emission in the Large Magellanic Cloud. These results allow the improvement of large-scale models of Galactic diffuse γ-ray emission and new measurements of the extragalactic γ-ray background.
- Publication:
-
Science with the New Generation of High Energy Gamma-ray Experiments
- Pub Date:
- March 2010
- DOI:
- 10.1063/1.3396000
- arXiv:
- arXiv:1002.1576
- Bibcode:
- 2010AIPC.1223...89T
- Keywords:
-
- astronomical telescopes;
- gamma-ray sources (astronomical);
- cosmic rays;
- interstellar matter;
- dark matter;
- magnetic field effects;
- 95.55.Ka;
- 95.85.Pw;
- 96.50.S-;
- 98.58.Ca;
- 95.35.+d;
- 95.85.Sz;
- X- and gamma-ray telescopes and instrumentation;
- gamma-ray;
- Cosmic rays;
- Interstellar dust grains;
- diffuse emission;
- infrared cirrus;
- Dark matter;
- Gravitational radiation magnetic fields and other observations;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Contribution to the Workshop SciNeGHe 2009/Gamma-ray Physics in the LHC era (Assisi - Italy, Oct. 7-9 2009)