Compatibility of the Huge-LQG with concordance cosmology

Compatibility of the large quasar groups with the concordance
cosmological model
Monthly Notices of the Royal Astronomical Society (2016), 461, 2267.

Compatibility of the large quasar groups with the concordance
cosmological model

Gabriel E. Marinello1, Roger G. Clowes1, Luis E. Campusano2,
Gerard M. Williger1,3, Ilona K. Söchting4 and Matthew J. Graham5

1 Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
2 Observatorio Astronómico Cerro Calán, Departamento de Astronomía, Universidad de Chile, Casilla 36-D, 7591245 Santiago, Chile
3 Department of Physics and Astronomy, University of Louisville, Louisville, KY 40292, USA
4 Astrophysics, Denys Wilkinson Building, Keble Road, University of Oxford, Oxford OX1 3RH, UK
5 California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA

We study the compatibility of large quasar groups with the concordance cosmological model.
Large quasar groups are very large spatial associations of quasars in the cosmic web, with sizes of 50–250 h−1 Mpc. In particular, the largest large quasar group known, named Huge-LQG, has a longest axis of ∼ 860 h−1 Mpc, larger than the scale of homogeneity (∼ 260 Mpc), which has been noted as a possible violation of the cosmological principle. Using mock catalogues constructed from the Horizon Run 2 cosmological simulation, we found that large quasar groups size, quasar member number and mean overdensity distributions in the mocks agree with observations. The Huge-LQG is found to be a rare group with a probability of 0.3 per cent of finding a group as large or larger than the observed, but an extreme value analysis shows that it is an expected maximum in the sample volume with a probability of 19 per cent of observing a largest quasar group as large or larger than Huge-LQG. The Huge-LQG is expected to be the largest structure in a volume at least 5.3 ± 1 times larger than the one currently studied.