On the angular distribution of IceCube high-energy events

TL;DR

This paper investigates the angular distribution of high-energy neutrino events detected by IceCube, finding modest evidence for anisotropy and suggesting sources may be either nearby or part of large-scale cosmic structures.

Contribution

It applies Monte Carlo techniques to analyze the isotropy of IceCube neutrino events, revealing potential anisotropies and insights into their cosmic origins.

Findings

Evidence of anisotropy in event distribution

Possible sources near the Milky Way or beyond 40 Mpc

Events organized in a fractal-like structure at cosmological distances

Abstract

The detection of high-energy astrophysical neutrinos of extraterrestrial origin by the IceCube neutrino observatory in Antarctica has opened a unique window to the cosmos that may help to probe both the distant Universe and our cosmic backyard. The arrival directions of these high-energy events have been interpreted as uniformly distributed on the celestial sphere. Here, we revisit the topic of the putative isotropic angular distribution of these events applying Monte Carlo techniques to investigate a possible anisotropy. A modest evidence for anisotropy is found. An excess of events appears projected towards a section of the Local Void, where the density of galaxies with radial velocities below 3000 km/s is rather low, suggesting that this particular group of somewhat clustered sources are located either very close to the Milky Way or perhaps beyond 40 Mpc. The results of further analyses of the subsample of southern hemisphere events favour an origin at cosmological distances with the arrival directions of the events organized in a fractal-like structure. Although a small fraction of closer sources is possible, remote hierarchical structures appear to be the main source of these very energetic neutrinos. Some of the events may have their origin at the IBEX ribbon.