Searches for correlation between UHECR events and high-energy gamma-ray Fermi-LAT data
The astrophysical sources responsible for ultra high-energy cosmic rays (UHECRs) continue to be one of the most intriguing mysteries in astrophysics. Here, we present a comprehensive search for correlations between high-energy (≳ 1 GeV) gamma-ray events from the Fermi Large Area Telescope (LAT) and UHECRs (≳ 60 EeV) detected by the Telescope Array and the Pierre Auger Observatory. We perform two separate searches. First, we conduct a standard cross-correlation analysis between the arrival directions of 148 UHECRs and 360 gamma-ray sources in the Second Catalog of Hard Fermi-LAT sources (2FHL). Second, we search for a possible correlation between UHECR directions and unresolved Fermi-LAT gamma-ray emission. For the latter, we use three different methods: a stacking technique with both a model-dependent and model-independent background estimate, and a cross-correlation function analysis. We also test for statistically significant excesses in gamma rays from signal regions centered on Cen A and the Telescope Array hotspot. There was no significant correlation is found in any of the analyses performed, except a weak (≲ 2σ) hint of signal with the correlation function method on scales ~ 1°. Upper limits on the flux of possible power-law gamma-ray sources of UHECRs are derived.
- Authors:
-
[1];
[2];
[3];
[4]
- Inst. of Physics Buenos Aires (IFIBA CONICET-UBA) and International Center for Advanced Studies (ICAS)(Argentina)
- RWTH Aachen Univ. (Germany). Inst. for Theoretical Particle Physics and Cosmology (TTK)
- NASA Goddard Space Flight Center (GSFC), Greenbelt, MD (United States). Astrophysics Division and NASA Postdoctoral Program Fellow
- Univ. of Nova Gorica (Slovenia). Lab. for Astroparticle Physics; National Inst. of Nuclear Physics (INFN), Trieste (Italy)
- Publication Date:
- Grant/Contract Number:
- AC02-76SF00515
- Type:
- Accepted Manuscript
- Journal Name:
- Journal of Cosmology and Astroparticle Physics
- Additional Journal Information:
- Journal Volume: 2016; Journal Issue: 12; Journal ID: ISSN 1475-7516
- Publisher:
- Institute of Physics (IOP)
- Research Org:
- SLAC National Accelerator Lab., Menlo Park, CA (United States)
- Sponsoring Org:
- USDOE
- Contributing Orgs:
- Fermi LAT Collaboration
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 79 ASTRONOMY AND ASTROPHYSICS; ultra high energy cosmic rays; gamma ray experiments; gamma ray theory
- OSTI Identifier:
- 1355719