Colloquium on 24 August 2017
Testing cosmological isotropy with the large-scale structure

Details

Title: Testing cosmological isotropy with the large-scale structure
Speaker: Dr. Carlos Bengaly (University of the Western Cape)
Date: Thursday, 24 August 2017
Time: 11:00 - 12:00
Venue: SAAO Auditorium

Abstract

The current standard model of cosmology, called ΛCDM, assumes that its background metric is Friedman-Lemaître-Robertson-Walker (FLRW) and the Universe is approximately homogeneous and isotropic on large scales, a feature of the so-called ’Cosmological Principle’ (CP). Despite the good agreement between ΛCDM and a plethora of cosmological observations, direct tests of the CP need to be performed in order to assess whether it is a valid hypothesis or just a mathematical simplification. In this talk, I will focus on a test of the cosmic isotropy using the angular distribution of WISExSCOS galaxy number counts (GNCs), in which we use the dipole anisotropy of these GNCs for this purpose, verifying if its amplitude is consistent with sets of ΛCDM-based mocks, and also if its direction agrees with other low-z probes. We obtain no strong evidence against the isotropy assumption, but we are still very limited by the systematics of the data,besides the possibility of large unaccounted low-z inhomogeneities especially in the z < 0.15 range. I will also briefly discuss other analyses I carried out with galaxy clusters and Type Ia Supernovae, in addition to future expectations of CP tests with the SKA.

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