A Giant Arc on the Sky

Abstract

We present the serendipitous discovery of a `Giant Arc on the Sky' at $z\sim 0.8$. The Giant Arc (GA) spans $\sim 1$ Gpc (proper size, present epoch), and appears to be almost symmetrical on the sky. It was discovered via intervening MgII absorbers in the spectra of background quasars, using the catalogues of Zhu \& Ménard. The use of MgII absorbers represents a new approach to the investigation of large-scale structures (LSSs) at redshifts $0.45\lesssim z\lesssim 2.25$. We present the observational properties of the GA, and we assess it statistically using methods based on: (i) single-linkage hierarchical clustering ($\sim 4.5\sigma$); (ii) the Cuzick-Edwards test ($\sim 3.0\sigma$); and (iii) power spectrum analysis ($\sim 4.8\sigma$). Each of these methods has distinctive attributes and powers, and we advise considering the evidence from the ensemble. We discuss our approaches to mitigating any {\it post-hoc} aspects of analysing significance after discovery. The overdensity of the GA is $\delta \rho /\rho \sim 1.3\pm 0.3$. The GA is the newest and one of the largest of a steadily accumulating set of very large LSSs that may (cautiously) challenge the Cosmological Principle, upon which the `standard model' of cosmology is founded. Conceivably, the GA is the precursor of a structure like the Sloan Great Wall (but the GA is about twice the size), seen when the Universe was about half its present age.

arXiv commentAccepted for MNRAS

References in corpus (39)

• The Sloan Digital Sky Survey Quasar Catalog V. Seventh Data Release
• The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release
• A Map of the Universe
• CMB Anomalies after Planck
• A Test of the Cosmological Principle with Quasars
• Evidence for anisotropy of cosmic acceleration
• The Kinematic Connection Between QSO-Absorbing Gas and Galaxies at Intermediate Redshift
• Evidence for a ~300 Mpc Scale Under-density in the Local Galaxy Distribution
• Probing cosmic isotropy with a new X-ray galaxy cluster sample through the $L_{\text{X}}-T$ scaling relation
• The JHU-SDSS metal absorption line catalog: redshift evolution and properties of Mg II absorbers
• Mapping extreme-scale alignments of quasar polarization vectors
• A structure in the early universe at z ~ 1.3 that exceeds the homogeneity scale of the R-W concordance cosmology
• Halo Gas Cross Sections And Covering Fractions of MgII Absorption Selected Galaxies
• What Determines the Incidence and Extent of MgII Absorbing Gas Around Galaxies?
• Confirmation of the existence of coherent orientations of quasar polarization vectors on cosmological scales
• Fractal Dimension as a measure of the scale of Homogeneity
• Alignment of quasar polarizations with large-scale structures
• Possible structure in the GRB sky distribution at redshift two
• Modeling the distribution of Mg II absorbers around galaxies using Background Galaxies & Quasars
• Seeing patterns in noise: Gigaparsec-scale `structures' that do not violate homogeneity
• A giant ring-like structure at 0.78<z<0.86 displayed by GRBs
• Excess Clustering on Large Scales in the MegaZ DR7 Photometric Redshift Survey
• Probabilistic multi-catalogue positional cross-match
• Galaxy Clusters from the DESI Legacy Imaging Surveys. I. Cluster Detection
• Discovery of a massive supercluster system at $z\sim 0.47$
• Two close Large Quasar Groups of size ~ 350 Mpc at z ~ 1.2
• Saraswati: An Extremely Massive ~ 200 Megaparsec Scale Supercluster
• Optical identifications of high-redshift galaxy clusters from Planck Sunyaev-Zeldovich survey
• The clustering of gamma-ray bursts in the Hercules-Corona Borealis Great Wall: the largest structure in the Universe?
• Cosmicflows-3: The South Pole Wall
• The galaxy luminosity function and the Local Hole
• Large Scale Structure at z=1.2 Outlined by MgII Absorbers
• Correlated orientations of the axes of large quasar groups on Gpc scales
• Searching for MgII absorbers in and around galaxy clusters
• HI 21-cm absorption from $z\sim 0.35$ strong MgII absorbers
• Large-scale clustering amongst Fermi blazars; evidence for axis alignments?
• The Redshift Distribution of Intervening Weak MgII Quasar Absorbers and a Curious Dependence on Quasar Luminosity
• Compatibility of the Large Quasar Groups with the Concordance Cosmological Model
• Re-Examining the Evidence of the Hercules-Corona-Borealis Great Wall

Cited by in corpus (20)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• Is the Observable Universe Consistent with the Cosmological Principle?
• The redshift dependence of the inferred $H_0$ in a local void solution to the Hubble tension
• Testing the local void hypothesis using baryon acoustic oscillation measurements over the last twenty years
• The binding of cosmological structures by massless topological defects
• The Scale of Homogeneity in the $R_h=ct$ Universe
• What if the universe expands linearly? A local general relativity to solve the "zero active mass" problem
• Spatially Homogeneous Universes with Late-Time Anisotropy
• The maximum extent of the filaments and sheets in the cosmic web: an analysis of the SDSS DR17
• Scanning the Universe for Large-Scale Structures using Gamma-Ray Bursts
• Analyzing the 21-cm signal brightness temperature in the Universe with inhomogeneities
• Time behaviour of Hubble parameter by torsion
• The Hidden Role of Anisotropies in Shaping Structure Formation in Cosmological N-Body Simulations
• Evolution of Cluster Alignments as Evidence of Large-scale Structure Formation in the Universe
• Constraining the Hubble parameter with the 21 cm brightness temperature signal in a universe with inhomogeneities
• Reanalysing large-scale structure using an updated gamma-ray burst spatial density approach
• Tracing the high-z cosmic web with Quaia: catalogues of voids and clusters in the quasar distribution
• Backreaction in cosmic screening approach
• Time evolution of the mutual information between disjoint regions in the Universe
• The Manticore Project II: Bayesian digital twins of cosmic structure across the SDSS and BOSS volumes