Investigating Ultra-Large Large-Scale Structures: Potential Implications for Cosmology

TL;DR

This paper reviews recent discoveries of extremely large cosmic structures, the Giant Arc and Big Ring, which challenge current cosmological models and suggest the need for new physics beyond the standard model.

Contribution

It introduces a novel method for mapping faint matter at intermediate redshifts and discusses the implications of these large structures for cosmology.

Findings

Giant Arc (~1 Gpc) and Big Ring (~400 Mpc) challenge the scale of homogeneity.

Both structures are at similar redshift and close on the sky.

These structures may indicate physics beyond the Standard Model.

Abstract

Large-scale structure (LSS) studies in cosmology map and analyse matter in the Universe on the largest scales. Understanding the LSS can provide observational support for the Cosmological Principle (CP) and the Standard Cosmological Model ($\Lambda$CDM). In recent years, many discoveries have been made of LSSs that are so large that they become difficult to understand within $\Lambda$CDM. Reasons for this are: they potentially challenge the CP, (i.e. the scale of homogeneity); and their formation and origin are not fully understood. In this article we review two recent LSS discoveries: the Giant Arc (GA, $\sim 1$ Gpc) and the Big Ring (BR, $\sim 400$ Mpc). Both structures are in the same cosmological neighbourhood -- at the same redshift $z \sim 0.8$ and with a separation on the sky of only $\sim 12^\circ$. Both structures exceed the often-cited scale of homogeneity (Yadav+ 2010), so individually and together, these two intriguing structures raise more questions for the validity of the CP and potentially hint at new physics beyond the Standard Model. The GA and BR were discovered using a novel method of mapping faint matter at intermediate redshifts, interpreted from the MgII absorption doublets seen in the spectra of background quasars.