The dark Universe in the light of its morphology

• Applicant: Dr. Alexander Wiegand
• Subject Area: Astrophysics and Astronomy
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 268308816

Over the last decade, galaxy redshift surveys have been extremely successful in measuring the structure of the galaxy distribution on ever larger scales. The large number of ongoing and planned spectroscopic surveys like BOSS, eBOSS, DESI, 4Most and Euclid will finally deliver a three dimensional map of a significant fraction of the observable universe.The aim of this project is to develop analysis tools that are based on Minkowski Functionals and fully exploit the wealth of information contained in this map of galaxy positions. In the era of precision cosmology, the supplement of information that we will access will be crucial to uncover the physical origin of the dark components that govern the fate of the universe.The four Minkowski Functionals we use uniquely quantify the shape of any extended body. The first functional gives the volume of the body, the second its surface area, the third its integrated mean curvature and the last its Euler characteristic. Together with a prescription that converts a set of points into a smooth body, the functionals characterize the complex shapes that we see in the distribution of galaxies, such as filaments and voids.This rich structure seen in galaxy surveys is not entirely captured by the usual analysis, based on the two-point correlation function. This latter only measures how strongly structure enhances the probability of finding two galaxies at a given distance from one another. The key advantage of using Minkowski Functionals is that, in addition to the standard two-point properties, they include information from all higher-order correlations, through an analytic relation. We will use this extra information in Minkowski Functionals to test cosmological models more precisely.To achieve this goal, we first analyse which cosmological parameters we can test the best with the method we will develop. In particular we will try to identify a standard ruler for a precise measurement of cosmic distances, and thus of dark energy. We will also attempt to use Minkowski Functionals to improve the analysis of the difference of clustering of dark matter and galaxies. In a next step, we will test commonly employed modelling assumptions which connect cosmological models to observations. In the third step, we will apply the method developed in the first step with the best modelling assumptions identified in the second step to perform a numerical test of cosmological models. To do so we will analyze current and future galaxy redshift surveys with our numerical codes.Finally, Minkowski Functionals are actively employed in different areas of Science from solid state physics, to biophysics and are even used in medical applications. Consequently, the impact of the theoretical methods and efficient codes we will develop during this project can go beyond cosmological applications.

• DFG Programme: Research Fellowships
• International Connection: USA
• Host: Professor Dr. Daniel Eisenstein