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An Indication of Anisotropy in Arrival Directions of Ultra-high-energy Cosmic Rays through Comparison to the Flux Pattern of Extragalactic Gamma-Ray Sources
- Source :
- Astrophysical Journal Letters, 853, 1-10, Astrophysical Journal Letters, 853(2):29. IOP PUBLISHING LTD, CONICET Digital (CONICET), Consejo Nacional de Investigaciones Científicas y Técnicas, instacron:CONICET, Repositório Institucional da USP (Biblioteca Digital da Produção Intelectual), Universidade de São Paulo (USP), instacron:USP, Astrophys.J., Astrophys.J., 2018, 853 (2), pp.L29. ⟨10.3847/2041-8213/aaa66d⟩, Astrophys.J., 2018, 853 (2), pp.L29. 〈10.3847/2041-8213/aaa66d〉, The Astrophysical journal letters, The Astrophysical journal letters, Bristol : IOP Publishing, 2018, 853 (2), pp.L29. ⟨10.3847/2041-8213/aaa66d⟩, Astrophysical Journal Letters, 853, 2, pp. 1-10, Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos), Agência para a Sociedade do Conhecimento (UMIC)-FCT-Sociedade da Informação, instacron:RCAAP, SEDICI (UNLP), Universidad Nacional de La Plata, instacron:UNLP, NASA Astrophysics Data System
- Publication Year :
- 2018
-
Abstract
- A new analysis of the dataset from the Pierre Auger Observatory provides evidence for anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate angular scale, which is indicative of excess arrivals from strong, nearby sources. The data consist of 5514 events above 20 EeV with zenith angles up to 80 deg recorded before 2017 April 30. Sky models have been created for two distinct populations of extragalactic gamma-ray emitters: active galactic nuclei from the second catalog of hard Fermi-LAT sources (2FHL) and starburst galaxies from a sample that was examined with Fermi-LAT. Flux-limited samples, which include all types of galaxies from the Swift-BAT and 2MASS surveys, have been investigated for comparison. The sky model of cosmic-ray density constructed using each catalog has two free parameters, the fraction of events correlating with astrophysical objects and an angular scale characterizing the clustering of cosmic rays around extragalactic sources. A maximum-likelihood ratio test is used to evaluate the best values of these parameters and to quantify the strength of each model by contrast with isotropy. It is found that the starburst model fits the data better than the hypothesis of isotropy with a statistical significance of 4.0 sigma, the highest value of the test statistic being for energies above 39 EeV. The three alternative models are favored against isotropy with 2.7-3.2 sigma significance. The origin of the indicated deviation from isotropy is examined and prospects for more sensitive future studies are discussed.<br />Instituto de Física La Plata
- Subjects :
- Astronomy
[ PHYS.ASTR ] Physics [physics]/Astrophysics [astro-ph]
Ciencias Físicas
cosmic radiation: density
galaxies: starburst
Astrophysics
01 natural sciences
purl.org/becyt/ford/1 [https]
methods: data analysis Supporting material: FITS file
Ultra-high-energy cosmic ray
data analysis [Methods]
Anisotropy
cosmic radiation: model
010303 astronomy & astrophysics
cosmic ray
High Energy Astrophysical Phenomena (astro-ph.HE)
Physics
OBSERVATÓRIOS
Settore FIS/01 - Fisica Sperimentale
Astrophysics::Instrumentation and Methods for Astrophysics
astroparticle physic
astroparticle physics
cosmic rays
galaxies: active
methods: data analysis Supporting material: FITS files
Astronomy and Astrophysics
Space and Planetary Science
Auger
observatory
gamma ray: emission
data analysis Supporting material: FITS file [methods]
Astrophysics - High Energy Astrophysical Phenomena
CIENCIAS NATURALES Y EXACTAS
Astrophysics - Cosmology and Nongalactic Astrophysics
Cosmology and Nongalactic Astrophysics (astro-ph.CO)
Active galactic nucleus
active [Galaxies]
Astrophysics::High Energy Astrophysical Phenomena
Data analysis
FOS: Physical sciences
Starburst
Cosmic ray
anisotropy
Astrophysics::Cosmology and Extragalactic Astrophysics
Otras Ciencias Físicas
GLAST
0103 physical sciences
High Energy Physics
cosmic radiation: UHE
AGN
Cosmic rays
Astrophysics::Galaxy Astrophysics
Zenith
Pierre Auger Observatory
SPECTRUM
010308 nuclear & particles physics
Isotropy
Física
purl.org/becyt/ford/1.3 [https]
Astronomy and Astrophysic
methods: data analysis
Galaxy
flux
starburst [Galaxies]
Experimental High Energy Physics
Active galaxies
galaxy
Astroparticle physics
[PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
statistical
Subjects
Details
- ISSN :
- 20418205 and 20418213
- Database :
- OpenAIRE
- Journal :
- Astrophysical Journal Letters, 853, 1-10, Astrophysical Journal Letters, 853(2):29. IOP PUBLISHING LTD, CONICET Digital (CONICET), Consejo Nacional de Investigaciones Científicas y Técnicas, instacron:CONICET, Repositório Institucional da USP (Biblioteca Digital da Produção Intelectual), Universidade de São Paulo (USP), instacron:USP, Astrophys.J., Astrophys.J., 2018, 853 (2), pp.L29. ⟨10.3847/2041-8213/aaa66d⟩, Astrophys.J., 2018, 853 (2), pp.L29. 〈10.3847/2041-8213/aaa66d〉, The Astrophysical journal letters, The Astrophysical journal letters, Bristol : IOP Publishing, 2018, 853 (2), pp.L29. ⟨10.3847/2041-8213/aaa66d⟩, Astrophysical Journal Letters, 853, 2, pp. 1-10, Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos), Agência para a Sociedade do Conhecimento (UMIC)-FCT-Sociedade da Informação, instacron:RCAAP, SEDICI (UNLP), Universidad Nacional de La Plata, instacron:UNLP, NASA Astrophysics Data System
- Accession number :
- edsair.doi.dedup.....189561935096fa2eb4178233a056a4df