Assist. Jon Judež

I am an astrophysicist at the University of Ljubljana, Faculty of Mathematics and Physics. I work as part of the research group led by Prof. Dr. Maruša Bradač. Our team utilizes data from the groundbreaking James Webb Space Telescope, enabling us to explore previously inaccessible regions of the universe. My primary focus is on investigating the earliest galaxies, studying their growth and evolution during the first billion years of cosmic history.

I completed my undergraduate studies in physics at the Faculty of Mathematics and Physics and pursued further education at Stockholm University, where I earned a Master's degree in astrophysics. During this time, I also gained valuable experience in research of planets orbiting other stars. Currently, I am a young researcher at our faculty, engaged in doctoral studies.

I am a member of the Near-Infrared Imager and Slitless Spectrograph (NIRISS) Guaranteed Time Observations (GTO) program CANUCS (CAnadian NIRISS Unbiased Cluster Survey). In the collaboration, we are using the data of five massive galaxy clusters obtained by the game-changing James Webb Space Telescope.

My research focuses on reconstruction of gravitationally lensed objects. In our data, we find numerous strongly lensed sources, which means they are magnified and distorted. I am working with a tool Lenstruction (Yang et al. 2020, Birrer & Amara 2018, and Birrer et al. 2015). By using the lensing models produced within our collaboration to perform forward modelling, I can infer the intrinsic properties of sources (sizes and shapes), just like if there was no distortion by lensing.

https://arxiv.org/abs/2412.04983

https://arxiv.org/abs/2502.07733