No indications of axionlike particles from Fermi
- Department of Physics, University of Chicago, Chicago, Illinois 60637-1433 (United States)
As very high energy (> or approx. 100 GeV) gamma rays travel over cosmological distances, their flux is attenuated through interactions with the extragalactic background light. Observations of distant gamma ray sources at energies between {approx}200 GeV and a few TeV by ground-based gamma-ray telescopes such as HESS, however, have motivated the possibility that the universe is more transparent to very high energy photons than had been anticipated. One proposed explanation for this is the existence of axionlike particles (ALPs) which gamma rays can efficiently oscillate into, enabling them to travel cosmological distances without attenuation. In this article, we use a state-of-the-art model for the extragalactic background light (which is somewhat lower at {approx}{mu}m wavelengths than in previous models) and data from the Fermi Gamma Ray Space Telescope to calculate the spectra at 1-100 GeV of two gamma-ray sources, 1ES1101-232 at redshift z=0.186 and H2356-309 at z=0.165, in conjunction with the measurements of ground-based telescopes, to test the ALP hypothesis. We find that these observations can be well fit by an intrinsic power-law source spectrum with indices of -1.72 and -2.1 for 1ES1101-232 and H2356-309, respectively, and that no ALPs or other exotic physics is necessary to explain the observed degree of attenuation. While this does not exclude the possibility that ALPs are involved in the cosmological propagation of gamma rays, it does reduce the motivation for such new physics.
- OSTI ID:
- 21537492
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 83, Issue 6; Other Information: DOI: 10.1103/PhysRevD.83.063005; (c) 2011 American Institute of Physics; ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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RED SHIFT
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BOSONS
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