The Giant Arc -- Filament or Figment?

TL;DR

The paper investigates the 'Giant Arc' of MgII absorbers, demonstrating that such large-scale patterns are common in a homogeneous universe and are not evidence of large-scale inhomogeneity.

Contribution

The study refutes claims that the 'Giant Arc' contradicts cosmological homogeneity by showing similar patterns are prevalent in random and simulated data.

Findings

Large patterns like the 'Giant Arc' are common in homogeneous universes.

Previous claims of contradiction are based on parameter choices that do not indicate inhomogeneity.

The pattern's ubiquity does not challenge the standard cosmological model.

Abstract

The so-called "Giant Arc" is a sparse pattern of MgII absorbers spanning approximately 740 comoving Mpc, whose discovery has been claimed to contradict the large-scale homogeneity inherent to the standard cosmological model. We previously showed that, with the same algorithm and parameters used for its discovery, very similar patterns are abundant in uniform random distributions, and among equivalent halo samples in a cosmological simulation of the standard model. In a response, the original discoverers of the "Giant Arc" have argued that these parameters were only appropriate for their specific observational data, but that a smaller linking length should be used for control studies, in which case far fewer patterns are detected. We briefly review and disprove these arguments, and demonstrate that large patterns like the "Giant Arc" are indeed ubiquitous in a statistically homogeneous universe.