Ultra-Large-Scale Structures in Cosmology

Ultra-large-scale structures in cosmology are physically huge (exceeding the estimated scale of homogeneity), statistically-significant features in the distribution of matter in the Universe. The accumulating list of uLSSs raises questions about the assumption of homogeneity on large scales, which the Cosmological Principle --- the foundation of the standard cosmological model --- requires. Alexia uses a method of mapping intervening absorption features detected in the spectra of bright, background quasars, to trace the underlying matter distribution. In particular, singly-ionised magnesium (MgII) is well known to trace galaxies and galaxy clusters.

Alexia will present the discovery of `A Giant Ring on the Sky’, which is a ring-like uLSS that appears to extend from the previously-reported Giant Arc. The Giant Ring (GR) is an almost contiguous, overdense filament of MgII absorbers which appears as a Giant Ring, approximately 1Gpc across, from our line of sight.

Nested rings (such as the BR and GR)…