Speaker
Description
The Cosmological Principle (CP) asserts that the universe is isotropic and homogeneous on large scales. It attributes the CMB thermal dipole to our local peculiar motion, hence giving rise to the term kinematic dipole. If this attribution is correct, then all-sky surveys of other cosmological probes should show a similar dipole in their distribution across the sky. More than forty years ago, researchers postulated the presence of a number-count dipole in the source distribution (dubbed the matter dipole) as a test of the CP. Over the years, a number of studies have calculated the matter dipole using cosmological surveys conducted at radio and infrared frequencies, and have reported a disagreement between the matter and kinematic dipoles. Recent results indicate that the disagreement between the two exceeds 5σ!
In this talk, I will present the first determination of the matter dipole at optical frequencies. We use Bayesian statistics to calculate the matter dipole in the Quaia quasar sample. While the inferred direction of the matter dipole is in agreement with the kinematic dipole, its amplitude exceeds that of the latter. Our results motivate the need for further investigation into this discrepancy and lay the groundwork for future analyses at higher frequencies.
DOI: doi.org/10.1093/mnras/stad3706