Bounds on the density of sources of ultra-high energy cosmic rays from the Pierre Auger Observatory

Abstract

We derive lower bounds on the density of sources of ultra-high energy cosmic rays from the lack of significant clustering in the arrival directions of the highest energy events detected at the Pierre Auger Observatory. The density of uniformly distributed sources of equal intrinsic intensity was found to be larger than ∼ (0.06 − 5) × 10 −4 Mpc −3 at 95% CL, depending on the magnitude of the magnetic deflections. Similar bounds, in the range (0.2 − 7) × 10 −4 Mpc −3 , were obtained for sources following the local matter distribution.

Can astrophysical neutrinos trace the origin of the detected ultra-high energy cosmic rays?

“…Besides cosmic ray-neutrino correlations and neutrinoneutrino correlations, limits on the local source density can also be obtained from cosmic ray-cosmic ray correlations. This is what the Pierre Auger Collaboration has done in Abreu et al (2013). The limits obtained there show that ρ 0 (0.06−7)×10 5 Gpc −3 , even stronger than the limits from the neutrino multiplet constraints, making it even less likely that neutrino-UHECR correlations will be found.…”

“…2 left panel). In addition, a different minimal energy threshold for cosmic rays is considered in Abreu et al (2013) compared with our results (E CR ≥ 60 EeV versus E CR ≥ 10 18.5 eV, respectively). It should also be noted that the bounds in Abreu et al (2013) were derived from the lack of significant clustering in arrival directions of the highest energy events detected at the Pierre Auger Observatory between 1 January 2004 and 31 December 2011.…”

“…In addition, a different minimal energy threshold for cosmic rays is considered in Abreu et al (2013) compared with our results (E CR ≥ 60 EeV versus E CR ≥ 10 18.5 eV, respectively). It should also be noted that the bounds in Abreu et al (2013) were derived from the lack of significant clustering in arrival directions of the highest energy events detected at the Pierre Auger Observatory between 1 January 2004 and 31 December 2011. By now, the number of detected events at these energies has increased significantly and hints of anisotropies have been found (Aab et al 2018;Caccianiga et al 2019), which could affect the bounds on the density of UHECR sources.…”

Gravitational slingshots around black holes in a binary

“…Incidentally, the population density for b 3000M tot , as displayed in the first row of Tb. 1, is just above the lower bound set by [75] according to clustering considerations (when assuming magnetic deflection angles appropriate for a mixed composition). Thanks to this large population, the demand on particle supply at each site is also lower in the steady case, for which [65]…”

“…Moreover, the number density of such BBH systems is very high (first two rows of Tb. 1), which contrasts with other possible steady sources such as clusters of galaxies or radio galaxies (at P op ∼ 1 − 10Gpc −3 , see e.g., [74]), and helps the RS mechanism to better reconcile with the lack of significant small scale clustering in observed UHECR directions [75,76]. Incidentally, the population density for b 3000M tot , as displayed in the first row of Tb.…”