Abstract

Invited Talk - Plenary

Tuesday, 16 September 2025, 11:30   (Kuppelsaal / virtual plenum)

Testing large scale cosmology with radio catalogues

Jonah Wagenveld
Max Planck Institute for Radio Astronomy

The cosmic radio dipole is an anisotropy in the number counts of radio sources, analogous to the dipole seen in the cosmic microwave background (CMB). Measurements of the radio dipole with large radio surveys have shown that although the radio dipole is aligned with the direction of the CMB dipole, the amplitudes are in disagreement, presenting a potential challenge to the cosmological principle itself. In this talk, I present my thesis work, in which I aimed to measure the cosmic dipole with large scale radio surveys. This includes the most sensitive measurement of the cosmic radio dipole at the time using novel Bayesian estimators. I will also focus on my measurement of the dipole with the MeerKAT Absorption Line Survey (MALS), a unique survey given its sparsity and depth compared to surveys more commonly used for dipole measurements. For this measurement, we aimed to understand all aspects of the survey, performing a deep analysis of the complete set of processing steps, from observations to cataloguing, to characterise and quantify potential systematic effects which could hamper a dipole measurement. I will detail the challenges and surprises of the dipole measurement using all MALS pointings, and the consequences of our results for understanding the nature of the cosmic radio dipole.