An important observational systematic are contributions by the cosmic infrared background (CIB) to the observed tSZ signal.
The CIB traces the same large-scale structures of matter in the Universe as does the tSZ effect and gravitational lensing. This makes disentangling these signals difficult. The Fellow quantified the effect of CIB contamination on the observed lensing-tSZ cross-correlation (Yan et al. 2019, arXiv:1809.09636).
In order to model the expected cross-correlation signal between gravitational lensing and the tSZ effect, the Fellow developed a new modelling framework that jointly describes the distribution of dark matter, gas, and stars in the Universe (Mead, Tröster et al. 2020, arXiv:2005.00009).
This model allowed for a detailed, quantitive forecasting of the constraining power of the planned joint analysis of cross-correlations of the gravitational lensing of galaxies, the tSZ effect, and lensing of the CMB. This forecasting analysis revealed that the envisaged joint analysis was suboptimal, since the cross-correlation between galaxy and CMB lensing contributes negligibly and the CMB lensing-tSZ cross-correlation is beset by observational systematics. On the other hand, it was found that joint analysis of cosmic shear, and the cross-correlation between weak lensing of galaxies and the tSZ has the potential to strongly constrain both cosmological parameters and the effects of galaxy formation, as set out in the objectives of the action.
To aid the statistical inference of the tSZ-lensing cross-correlation analysis, the Fellow developed a method to augment dark-matter only simulations with gas using deep learning techniques (Tröster et al. 2019, arXiv:1903.12173). This important development allows the rapid generation of mock data that would otherwise require running computationally very expensive hydrodynamical simulations that incorporate galaxy formation.
In preparation of the joint analysis of cosmic shear and the tSZ-lensing cross-correlation, the Fellow joined the Kilo-Degree Survey team to gain expertise in the analysis of cosmic shear data and develop the required tools, resulting in a number of high-impact publications (among others: Tröster et al. 2020, arXiv:1909.11006; Asgari, Tröster et al. 2020, arXiv:1910.05336; Hildebrandt et al. 2020, arXiv:1812.06076).
Resampling techniques, such as the bootstrap, are an attractive statistical method to find the properties of observed data, such as their statistical uncertainty. To validate the performance of these methods they can be inspected in simplified situations where the exact result is know. For the case of two-point correlations, such as the proposed lensing-tSZ cross-correlation, it was found that no such exact result exists, neither in the astronomy nor statistics literature. The Fellow as now derived this exact result (Tröster, 2020, in prep.).
The results of the action were disseminated in international conferences and workshops (nine in total, including invited and contributed talks), as well as, scientific publications. At the time of this report, the actions has produced 15 publications, of which 13 have been peer-reviewed.
No website has been developed for the project.
