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SEAGLE - Simulating EAGle LEnses

Deciphering galaxy formation via strong lens simulations
PhD ceremony:Mr S. (Sampath) Mukherjee
When:January 11, 2019
Supervisors:prof. dr. L.V.E. (Léon) Koopmans, prof. dr. J. Schaye
Co-supervisor:dr. R.B. Metcalf
Where:Academy building RUG
Faculty:Science and Engineering
SEAGLE - Simulating EAGle LEnses

Strong gravitational lensing is a robust tool for studying the mass structure and evolution of early-type galaxies (ETGs). In this thesis, I introduce the SEAGLE (i.e. Simulating EAGLE LEnses) pipeline, that approaches the study of galaxy formation through strong gravitational lensing, using a suite of high-resolution hydrodynamic simulations, Evolution, and Assembly of GaLaxies and their Environments (EAGLE) project. I showed that the galaxy evolution models with either too weak or too strong stellar and/or AGN feedback fail to explain the distribution of observed mass-density slopes. On the other hand, models with constant stellar feedback, or AGN feedback with a higher duty cycle but milder temperature increases of their surrounding gas, produce strong lenses with total mass density slopes close to isothermal. For the first time, I discovered a major discrepancy between simulations and strong lensing observations in their projected dark matter fraction within half of the effective radius. This discrepancy is however lifted when a variable bottom heavy stellar initial mass function (IMF) is used in the simulation. This could also indicate a yet unaccounted dependency of the properties of ETGs on stellar and AGN feedback and the assumed stellar IMF. In this thesis, I have investigated some of the key but open questions related to galaxy formation via strong lensing and opened up some new thought-provoking questions for the future.