Probing the Dipole of the Diffuse Gamma-Ray Background

  1. Kashlinsky, A. 245
  2. Atrio-Barandela, F. 1
  3. Shrader, C. S. 23
  1. 1 Universidad de Salamanca
    info

    Universidad de Salamanca

    Salamanca, España

    ROR https://ror.org/02f40zc51

  2. 2 Goddard Space Flight Center
    info

    Goddard Space Flight Center

    Greenbelt, Estados Unidos

    ROR https://ror.org/0171mag52

  3. 3 Catholic University of America
    info

    Catholic University of America

    Washington, Estados Unidos

    ROR https://ror.org/047yk3s18

  4. 4 SSAI, Lanham, MD 20770, USA
  5. 5 University of Maryland, College Park
    info

    University of Maryland, College Park

    College Park, Estados Unidos

    ROR https://ror.org/047s2c258

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Revista:
The Astrophysical Journal Letters

ISSN: 2041-8205,  2041-8213

Año de publicación: 2024

Volumen: 961

Número: 1

Páginas: L1

Tipo: Artículo

DOI: 10.3847/2041-8213/ACFEDD GOOGLE SCHOLAR lock_openAcceso abierto editor

Otras publicaciones en: The Astrophysical Journal Letters

Resumen

We measured the dipole of the diffuse γ-ray background (DGB), identifying a highly significant time-independent signal coincidental with that of the Pierre Auger UHECR. The DGB dipole is determined from flux maps in narrow energy bands constructed from 13 yr of observations by the Large Area Telescope (LAT) of the Fermi satellite. The γ-ray maps were clipped iteratively of sources and foregrounds similar to that done for the cosmic infrared background. The clipped narrow energy band maps were then assembled into one broad energy map out to the given energy starting at E = 2.74 GeV, where the LAT beam falls below the sky's pixel resolution. Next we consider cuts in Galactic latitude and longitude to probe residual foreground contaminations from the Galactic plane and center. In the broad energy range 2.74 < E ≤ 115.5 GeV, the measured dipoles are stable with respect to the various Galactic cuts, consistent with an extragalactic origin. The γ-ray sky's dipole/monopole ratio is much greater than that expected from the DGB clustering component and the Compton–Getting effect origin with reasonable velocities. At ≃(6.5–7)% it is similar to the Pierre Auger UHECRs with EUHECR ≥ 8 EeV, pointing to a common origin of the two dipoles. However, the DGB flux associated with the found DGB dipole reaches parity with that of the UHECR around EUHECR ≤ 1 EeV, perhaps arguing for a non-cascading mechanism if the DGB dipole were to come from the higher-energy UHECRs. The signal-to-noise ratio of the DGB dipole is largest in the 5–30 GeV range, possibly suggesting the γ-photons at these energies are the ones related to cosmic rays.

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Financiadores

  • NASA Fermi
    • 80NSSC20K1597

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