Research ArticleASTRONOMY

Filaments of galaxies as a clue to the origin of ultrahigh-energy cosmic rays

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Science Advances  02 Jan 2019:
Vol. 5, no. 1, eaau8227
DOI: 10.1126/sciadv.aau8227
  • Fig. 1 Hammer projection of nearby galaxies within 50 Mpc (gray dots) and TA UHECR events above 5.7 × 1019 eV (large black dots) in equatorial coordinates.

    The concentration of galaxies, represented by dark gray dots, is the Virgo Cluster. The red square marks the center of the TA hotspot. The pink and sky blue lines indicate the Galactic and Supergalactic planes, respectively. The purple line indicates the field of view limit of the TA experiment.

  • Fig. 2 Six filaments of galaxies connected to the Virgo Cluster, F1 to F6.

    The color dots show the galaxies that belong to the filaments, and the color lines draw the spines of the filaments. The color codes the distance from us to the galaxies and the spines (h is the Hubble parameter). The TA events above 5.7 × 1019 eV (large black dots), nearby galaxies within 50 Mpc (gray dots), the Virgo Cluster galaxies (dark gray dots), and the center of the TA hotspot (red square) are also shown.

  • Fig. 3 Cumulative binomial probability for the excess of TA hotspot events around filaments F1 to F3 as a function of angular separation.
  • Fig. 4 Schematic drawing of a model for the origin of TA hotspot events.

    UHECRs are postulated to be produced at a source or sources inside the Virgo Cluster. After they are confined by cluster magnetic fields and roam around for a while, UHECRs escape to the filaments connected to the cluster. Then, they propagate along the filaments. Some of them are eventually scattered by the random component of magnetic fields and may come to our Galaxy. Here, the Virgo Cluster, represented by a gray circle, and filaments F1 to F6 are plotted in the Supergalactic coordinates. Our Galaxy is located at the coordinate origin.

  • Fig. 5 Trajectories of two UHE protons with 6 × 1019 eV around a simulated cluster.

    The cluster has the x-ray weighted temperature, T = 3.5 keV, and the core magnetic field of ~1.5 μG. Colors code the magnetic field strength; the cluster is represented by the blue tone, while filaments are represented by the red tone. The box drawn with white lines has the volume of 42 × 17.5 × 17.5 (h−1 Mpc)3. The trajectories are plotted with white dots.

  • Fig. 6 Displacement of two UHE protons, shown in Fig. 5, from their launching positions.

    Case 1 is the one shown in the top panel of Fig. 5, and case 2 is in the bottom panel. Colors map the magnetic field strength that the UHECRs experience.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/1/eaau8227/DC1

    Supplementary Materials

    Fig. S1. Leo Minor filament, or F3, in the three-dimensional Supergalactic coordinates.

    Fig. S2. Six filaments dynamically connected to the Virgo Cluster and their names.

    Fig. S3. Blow-up of a sky region including the Virgo Cluster and filaments F1 to F3.

    Data File S1. Sky positions of galaxies for six filaments connected the Virgo Cluster.

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Materials
    • Fig. S1. Leo Minor filament, or F3, in the three-dimensional Supergalactic coordinates.
    • Fig. S2. Six filaments dynamically connected to the Virgo Cluster and their names.
    • Fig. S3. Blow-up of a sky region including the Virgo Cluster and filaments F1 to F3.
    • Data File S1. Sky positions of galaxies for six filaments connected the Virgo Cluster.

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