## Luminous and Dark Matter in Massive Early-type Galaxies with Weak Gravitational Lensing and the KiDS-1000 Cosmic Shear Power Spectrum

Maryam Tajalli

The stellar initial mass function (IMF) is one of the fundamental properties of stellar populations and detecting a variation of the IMF with galaxy properties can give us insight into the physics of star formation. However, determining the stellar IMF of massive galaxies is still one of the open problems in cosmology. Future space-based surveys, such as Euclid, will provide unprecedented weak lensing shape measurements on scales of a few tens of kpc, enabling us to probe the very inner regions of galaxies. In the first part of this talk, I will present forecasted constraints on the stellar IMF and stellar-to-halo mass relation of massive early-type galaxies from the future Euclid survey based on the Bayesian hierarchical inference formalism that we have developed.

I will show that Euclid is expected to provide an answer to the question of whether the stellar IMF is a universal function or not. In the second part of the talk, I will describe our efforts to develop a survey-independent approach to obtain cosmological parameter constraints from cosmic shear measurements, given that there are signs of disagreements between the three main cosmic shear surveys currently reporting constraints on cosmological parameters (KiDS, DES, HSC). I will discuss how we reconstruct the three sets of KiDS-1000 two-point statistics (shear two-point correlation functions, band powers, Complete Orthogonal Sets of E/B-Integrals (COSEBIs)) by replacing survey-specific redshift distribution of galaxies in tomographic bins with standard functions, and derive constraints on cosmological parameters (σ8and ΩM) using COSMOSIS and the KiDS Cosmology Analysis Pipeline (KCAP).