PhD Thesis Defense: Georgios Zacharegkas

10:00–11:00 am ERC 501

Georgios Zacharegkas "Modeling the non-linear scales in Cosmology via the galaxy-halo connection with applications in DES Y3"

We develop a framework to model the non-linear scales around galaxies in cosmological two-point functions. Our model is able to model the small scales that are usually ignored in cosmological analyses due to our limited understanding of how to consistently model them simultaneously with the linear scales while analyzing the data.

We utilize the Halo Occupation Distribution (HOD) model to push analyses of galaxy-galaxy lensing and galaxy clustering deep into the non-linear regime. We have successfully applied our model to data from the Dark Energy Survey (DES) in order to constraint the relation between galaxies and their host dark matter halos. For the first application, we have reanalyzed the galaxy samples used in DES Year 3 (Y3) for the key cosmological studies and we were able to constrain the average halo mass, satellite fraction and galaxy bias of the lenses via galaxy-galaxy lensing alone. In the second application we expand our model to include galaxy clustering and more features of the galaxy-halo connection and we generated a new lens galaxy sample with which to perform a joint lensing and clustering analysis.

We conclude that our framework is successful in describing the data. Therefore, our results motivate further investigation on how small scales can improve data analysis from galaxy surveys. Using a framework such as our HOD model we can not only constrain the galaxy-halo connection, which is important for cosmology and astrophysics by itself, but also potentially improve the constraints on the cosmological parameters.

Event Type

PhD Thesis Defenses

Jul 14