A Giant Ring on the sky

TL;DR

This paper reports the discovery and analysis of a large-scale ring-like structure at redshift ~0.8, supported by multiple statistical methods and evidence, suggesting a complex, overlapping cosmic feature.

Contribution

It introduces the discovery of a giant ring structure, supported by novel statistical assessments and the identification of overlapping features in large-scale cosmic data.

Findings

Two >4σ elliptical features consistent with the ring prediction and visual identification.

Significant clustering detected at scales of approximately 320 Mpc.

Random and simulated data do not replicate the observed ring features.

Abstract

We present the discovery of `A Giant Ring on the Sky' (GR); a ring-like, ultra-large-scale structure at z~0.8, located in the same field that contains the previously-documented Giant Arc (GA) and Big Ring (BR). The GR was predicted from the presence of a Northern Arc (NA) filament (noted in previous work), which looked like it could, with more or enhanced data, connect with the GA to form a giant ring that encompasses the BR. There is now much evidence to support the reality of a GR. There appear to be two overlapping versions of the GR which differ by only the left-hand-side trajectory; this branching in the LHS of the GR was identified with the FilFinder algorithm and appears to correspond to both the GR prediction (the extended, elliptical, GR from the GA+NA ellipse), and the visually-identified ellipse (the visually-impressive, almost contiguous, roughly circular, GR which is enhanced by a tilted viewing angle). The branching in the GR seems to be hinting at multiple, overlapping ring features. The GR consists of a thin, filamentary northern region, a clustered, ambiguous southern region (including the members of the GA), and filamentary branching towards the LHS. Statistical assessment with elliptical shells, and optimum elliptical-shell-matching, identified two $> 4\sigma$ ellipse features corresponding to the GR prediction and to the visually-identified GR. Additionally, the 2D Power Spectrum Analysis identified significant ($3.5 \sigma$) clustering on scales ~320Mpc. We also applied our statistical assessments to random data and to FLAMINGO-10K simulated data. The results demonstrate that, while superficially `significant' elliptical shells can be reproduced in random data with the optimum ellipse-matching method (many trials giving the `look-elsewhere' effect), with 2D PSA all of the random fields, and FLAMINGO-10K fields, were found to be entirely consistent with random.