Niko Šarčević is a cosmologist working at Newcastle University, and is part of the LSST DESC. Her research focuses on modelling and mitigating the intrinsic alignment of galaxies in weak lensing measurements. She is also interested in the statistical problems for late-time cosmology. Niko has previously worked in the XENON collaboration where she designed the electric field cage of XENONnT detector. Apart from research, Niko is absolutely obsessed with data visualization, she very much enjoys teaching, and the writing/editing/reviewing process. You can find Niko on Twitter/X @NikoSarcevic
Title: Joint modeling of astrophysical systematics for cosmological surveys
Abstract: In this talk, I will present a novel framework for modeling the weak lensing source galaxy redshift distribution and galaxy intrinsic alignment via a shared luminosity function. In the context of LSST Year 1 and Year 10 cosmic shear analysis, I demonstrate the significant impact of the luminosity function on source galaxy redshift distributions and intrinsic alignment contamination. I establish the influence of Schechter luminosity function parameters on the redshift distribution of a magnitude-limited sample and show the effects of marginalizing over these parameters in intrinsic alignment modeling. I forecast how this joint modeling approach affects cosmological parameter constraints, finding that it yields constraints comparable to standard analyses while mitigating potential biases from incorrectly fixed luminosity function parameters. I highlight the specific impact of the luminosity function shape on the cosmic shear data vector and discuss the method's potential for modeling generic selection functions and extending to a 3x2pt analysis with galaxy bias incorporation. While focused on LSST cosmic shear, this framework is broadly applicable to weak lensing surveys.