UHECR deflections in the coherent Galactic magnetic field

Abstract

We study the deflections of ultra-high-energy cosmic rays in several widely used models of the coherent Galactic magnetic field (GMF), including PT11 (Pshirkov et al. [1]), JF12 (Jansson and Farrar [2]), UF23 (Unger and Farrar [3]) and KST24 (Korochkin, Semikoz, and Tinyakov [4]). We propagate particles with rigidities of 5, 10, and 20 EV and analyze the differences in deflection predictions across these GMF models. We identify the GMF components responsible for deflections in various regions of the sky and discuss the uncertainties in modeling these components, as well as potential future improvements.

Figures (5)

• Figure 1: Angular deflections of $R=20$ EV (upper panels) and $R=10$ EV (lower panels) particles in PT11, JF12, UF23 base and KST24 models of the coherent GMF. The position of the dipole is for the energies $E^\mathrm{TA}_\mathrm{Auger} \ge {}^{10~\mathrm{Eev}}_{8.55~\mathrm{Eev}}$ from PierreAuger:2023mvf. The skymaps are shown in the Galactic coordinates using the Mollweide projection. The Galactic center is at the center of the maps and longitude increases to the left. Note that all small-scale features visible on the maps will be washed out by the turbulent GMF, see Sec. \ref{['sec:defl_turb']} for details.
• Figure 2: Same as Fig. \ref{['fig:defl_skymaps']} but for particles with a rigidity of $R=5$ EV.
• Figure 3: Histogram of angular deflections of $R=10$ EV particles, backtracked in PT11, JF12, UF23 base and KST24 GMF models. The initial momenta of the particles were uniformly distributed over the sky, corresponding to the centers of the pixels in the HEALPix binning scheme with $\mathrm{NSIDE}=128$. The arrows indicate the medians of the corresponding distributions.
• Figure 4: Directions of deflections of $R=20$ EV particles after backtracking in the JF12, UF23 (all eight models), and KST24 GMF models. The initial directions of the particles are shown with dots. The final directions at the edge of the Galaxy are marked with arrows for the KST24 model and encircled with colored ellipses for the JF12 and UF23 collection of models. Different colors correspond to different particles' initial latitudes for better visibility.
• Figure 5: Localization of the source of the Amaterasu particle. The observed direction of Amaterasu is shown with a blue dot. A purple contour shows the localization using KST24 model assuming Amaterasu is an iron nucleus. A green contour corresponds to a localization region obtained in Unger:2023hnu for the UF23 collection of models. For both contours the Amaterasu energy was rescaled to $E=212$ EeV to account for the systematic bias of the energy reconstruction for the heavy primaries TelescopeArray:2023sbd. Black stars mark bright starburst galaxies from the catalog of 2019JCAP...10..073L.