Exploring the superwind mechanism for generating ultrahigh-energy cosmic rays using large-scale modeling of starbursts

Luis A. Anchordoqui and Diego F. Torres

Phys. Rev. D 102, 023034 – Published 27 July 2020

Abstract

The Pierre Auger collaboration has provided a compelling indication for a possible correlation between the arrival directions of ultrahigh-energy cosmic rays and nearby starburst galaxies. Herein we show how the latest large-scale modeling of starburst galaxies is compatible with the cosmic rays producing the anisotropy signal being accelerated at the terminal shock of superwinds.

Received 27 April 2020
Accepted 16 July 2020

DOI:https://doi.org/10.1103/PhysRevD.102.023034

Physics Subject Headings (PhySH)

Cosmic ray acceleration Cosmic ray sources

Gravitation, Cosmology & Astrophysics

Authors & Affiliations

Luis A. Anchordoqui^1,2,3 and Diego F. Torres ^4,5,6

¹Department of Physics and Astronomy, Lehman College, City University of New York, New York, New York 10468, USA
²Department of Physics, Graduate Center, City University of New York, New York, New York 10016, USA
³Department of Astrophysics, American Museum of Natural History, New York, New York 10024, USA
⁴Institute of Space Sciences (ICE-CSIC), Campus UAB, Carrer de Magrans s/n, 08193 Barcelona, Spain
⁵Institució Catalana de Recerca i Estudis Avanćats (ICREA), E-08010 Barcelona, Spain
⁶Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain

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Vol. 102, Iss. 2 — 15 July 2020

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Figure 1
Model flux skymap of UHECR emission from the 23 brightest nearby starbursts, with a radio flux larger than 0.3 Jy (selected out the 63 objects within 250 Mpc search for $γ$ -ray emission by the Fermi-LAT collaboration [14]) [11]. The continuum emission at 1.4 GHz has been used as a proxy to weight the UHECR emission and an attenuation factor accounting for energy losses incurred by UHECRs during propagation has been included. The map has been smoothed using a Fisher-Von Mises distribution with concentration parameter corresponding to a search radius of 15.0° [12]. The color scale indicates the probability density of the source skymap as a function of position on the sky. The hot spot near the Galactic South Pole originates in NGC 253, located at Galactic coordinates ( $l = 97.4 °$ , $b = - 88 °$ ); the hot spot concentrated in the north-left region of the map is dominated by M82 ( $l = 141.4 °$ , $b = 40.6 °$ ); the hot spot near the Galactic plane on the right-side of the map is dominantly produced by NGC 4945 ( $l = 305 °$ , $b = 13.3 °$ ), but it has a non-negligible contribution from M83 ( $l = 314.6 °$ , $b = 32 °$ ). The white dashed line indicates the Supergalactic Plane. This figure is courtesy of Toni Venters.
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Figure 2
The evolution of $⟨ X_{\max} ⟩$ (left) and $σ (X_{\max})$ (right) with energy in comparison with the predictions of extensive air shower simulations generated using the post-LHC hadronic interaction model EPOS-LHC. For details see [16].
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Figure 3
The ratio $B_{\exp} / B_{pow}$ along the minor axis, i.e., for $R = 0$ for model $B^{'}$ .
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Figure 4
The ratio $B_{pow} (R, z) / B_{pow} (R = 0, z)$ for model $B^{'}$ , with $R = 0.5$ , 1, 2 kpc downwards.
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Figure 5
Energy loss during the acceleration process. The solid lines indicate the time independent cutoff energy for each particle species. This would be a brainwork situation in which the source produces an infinite number of identical shocks, with fresh injection at each shock and decompression between the shocks, such that the acceleration timescale $≫ 50 Myr$ [74, 75, 76, 77]. It is very unlikely that particles above the cutoff energy would have not suffered at least one photodisintegration. The bands encompass 68% of the nuclei in the statistical sample. This means that only 16% of the nuclei would reach energies above the upper border of the shaded bands and 16% would only reach energies below the lower border. The dashed lines indicate the maximum acceleration energy as given by (2) in a time period of 50 Myr. This means that the maximum energy attained by the particles is the minimum between the solid and dashed lines: $E_{\max} = \min$ (solid, dashed) lines, for each particle species. Note that for a timescale of 50 Myr, the particles cannot reach extreme energies unless the magnetic field is $O (100 μ G)$ . For $τ \sim 50 Myr$ and $15 ≲ \bar{B} / μ G ≲ 150$ , the photodisintegration energy loss for particle species with $Z < 10$ can be neglected, and the maximum energy is given by (2).
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Physical Review D

covering particles, fields, gravitation, and cosmology

Exploring the superwind mechanism for generating ultrahigh-energy cosmic rays using large-scale modeling of starbursts

Luis A. Anchordoqui and Diego F. Torres

Phys. Rev. D 102, 023034 – Published 27 July 2020

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Physical Review D

covering particles, fields, gravitation, and cosmology

Exploring the superwind mechanism for generating ultrahigh-energy cosmic rays using large-scale modeling of starbursts

Luis A. Anchordoqui and Diego F. Torres

Phys. Rev. D 102, 023034 – Published 27 July 2020

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