Silvan Fischbacher

Research area

I am a PhD student in the Cosmology Research Group of Prof. Refregier since November 2021. I am a member of the Dark Energy Survey (DES) and the Vera Rubin Observatory's Legacy Survey of Space and Time (LSST). My research focuses on cosmic shear analysis, particularly on systematics like intrinsic alignment and photometric redshifts.

In my first project (see JCAP01(2023)033), we investigated how systematic redshift errors are coupled to intrinsic alignment modelling. As one of the main results, we calculated the redshift requirements for current and upcoming surveys for different intrinsic alignment models.

My current work focuses on GalSBI, a phenomenological galaxy population model that is constrained by data using simulation-based inference. GalSBI models the galaxy population with analytical descriptions of galaxy luminosity functions, morphologies and spectral energy distributions. In arXiv:2412.08701, we constrained the parameters of the model by comparing image simulations with HSC deep field data using iterative Approximate Bayesian Computation. The simulated images are created with UFig and include a forward model of instrumental, observational, and source extraction effects. To accelerate the analysis, we developed an emulator based on a detection classifier and a normalizing flow. GalSBI is an open-source project, and the galsbi Python package is described in arXiv:2412.08722. Additionally, we released UFig publicly, as detailed in arXiv:2412.08716.