The clustering of gamma-ray bursts in the Hercules–Corona Borealis Great Wall: the largest structure in the Universe?

Abstract

The Hercules–Corona Borealis Great Wall is a statistically significant clustering of gamma-ray bursts around redshift 2. Motivated by recent theoretical results indicating that a maximal Universal structure size may indeed coincide with its estimated size (2−3 Gpc), we reexamine the question of this Great Wall’s existence from both observational and theoretical perspectives. Our statistical analyses confirm the clustering’s presence in the most reliable data set currently available, and we present a video showing what this data set looks like in 3D. Cosmological explanations (i.e. having to do with the distribution of gravitating matter) and astrophysical explanations (i.e. having to do with the rate of star formation over cosmic time and space) regarding the origin of such a structure are presented and briefly discussed, but the role of observational bias is also noted to be possibly serious. This, together with the scientific importance of using gamma-ray bursts as unique cosmological probes, emphasises the need for future missions such as the THESEUS satellite which will provide us with unprecedentedly homogeneous data of gamma-ray bursts with measured redshifts. We conclude from all this that the Hercules–Corona Borealis Great Wall may indeed be the largest structure in the Universe – but to be able to decide conclusively whether it actually exists, we need THESEUS.

Large-scale clustering amongst Fermi blazars; evidence for axis alignments?

“…In the widely accepted concordance model of cosmology the largest structures expected in the Universe are 1 Gpc (Yadav et al, 2010;Marinello et al, 2016). However, there have been observational claims for the detection of significantly larger structures, for example amongst the polarization alignments of quasars (Hutsémekers, et al, 1998(Hutsémekers, et al, , 2005(Hutsémekers, et al, , 2011 and amongst GRBs (Horváth et al, 2014, Horváth et al 2020, Balazs et al, 2015.Since these claims, if substantiated, would have profound implications for large scale structure formation it is important to see if it is possible to find independent evidence to back them up.…”

“…• The clustering of radio source axes on scales of 6 degree in the LoTSS survey (Osinga et al 2020, arXiv:2008 • The claim that gamma ray bursts are clustered on scales of tens of degrees (Horváth et al 2015, Horváth et al 2014, Horváth et al 2020.…”

Can an infinitely long object fit in an expanding universe?

“…While questions regarding the fundamental nature of expanding space may seem esoteric, it is interesting to consider the potential physical implications of relativistic peculiar velocity decays within our own universe. Super-clusters form filaments that can span up to 10 Gly, occupying up to 5% of the observable universe (Horvath, Hakkila, & Bagoly 2013). Given the existence of structure at such large scales, it is interesting to consider whether analogues of proper tethers exist on cosmological scales.…”

Local alignments of parsec-scale AGN radiojets

“…On the other hand, there are works that dispute this violation (e.g., Nadathur 2013) or even question the existence of these structures (e.g., Ukwatta & Woźniak 2016;Christian 2020). The discussion is still inconclusive but future missions are expected to provide more decisive results (Horvath et al 2020).…”