Gravitationally Imaging Dark Matter (MPRG)

Gravitationally Imaging Dark Matter (MPRG)

Strong gravitational lensing is a powerful tool to investiagete a wide range of astrophysical phenomena. Our group focuses on deriving observational constraints on the properties of dark matter, the interplay between dark matter physics and baryonic processes and its effect on the physics of structure formation. By constraining the detailed physical properties of high-redshift lensed galaxies we also aim to quantify star formation processes and AGN activity at cosmologically-interesting epochs on sub-kpc scales. We constantly develop new approaches to gravitational lens modelling and the analysis of high-angular resolution data from optical imaging and radio/mm/sub-mm interferometeric observations.

Group members:

Dr. Simona Vegetti

Vegetti, Simona

Scientific Staff

My research focuses on the nature of dark matter and on the connection between computational astrophysics and observational data. I use numerical simulations to derive predictions and constrains on dark matter models, comparing them with observational probles, such as strong gravitational lensing. In particular, I analyze the effects of warm and self-interacting dark matter, as well as their interplay with the baryonic component, running high-resolution simulations and then link their properties to the evolution of large scale structures.

Wolfgang Enzi

Enzi, Wolfgang

PhD student

In my research, I consider galaxy-galaxy strong gravitational lens systems to study the nature of dark matter. Low-mass dark matter haloes within these lens systems give rise to perturbations in the observed images of the background galaxies, thereby making their presence apparent even when they are non-luminous. Studying these perturbations requires an accurate description of the lenses overall mass distribution. For this reason, I develop new statistical methods to infer the mass distribution of the main lens and derive constraints on the mass function of dark haloes.

My work focuses on the analysis of galaxy-galaxy strong lensing observations from the Hubble Space Telescope and Keck II, that were collected by the SHARP program. The aim of the project is to gravitationally detect low-mass dark matter haloes with masses in the regime between 10^8 and 10^9 solar masses. My goal is to deliver observational constraints on the low-mass end of the halo mass function and test predictions from different dark matter models. 

Simon Ndiritu

Ndiritu, Simon

PhD student

My work aims at using strong gravitational lensing observations to measure the properties of magnetic fields in distant galaxies. To this end, I am developing a lens modelling code that simultaneously reconstructs the source surface brightness distribution in its four polarisation states and the magnetic field of the lens via differential Faraday rotation of the lensed images. By analysing VLBI and LOFAR data, and comparing the results with magnetohydrodynamical simulations of galaxy formation, I aim to understand the evolution of magnetic fields in galaxies and their influence on the properties of the galaxies themselves.

My work focuses on the search for low-mass dark matter haloes, with the goal of constraining dark matter particle models via the halo mass function. The main component of my work is to develop a gravitational lens modelling code to handle very long baseline interferometric (VLBI) radio data. This is advantageous because our ability to measure the abundance of low-mass dark matter haloes depends strongly on the angular resolution of the observation. While VLBI provides some of the best angular resolution in astronomy these datasets are large and therefore present unique computational challenges for modelling.

I am interested in the ways in which galaxies form and evolve across cosmic time. In particular, my research focuses on the galaxy kinematics. Trough this kind of studies, I learn how different physical processes shaped the variety of galaxies that we observe today. During my PhD, I developed a Bayesian lens modelling methodology, that offers the unique opportunity to exploit the great spatial resolution and signal-to-noise ratio achievable with gravitational lensing to perform a robust analysis of the kinematic properties of high-z lensed galaxies.

I work on Bayesian modelling of strong gravitational lensing by galaxy clusters. After having finished my master's degree at the Ludwig Maximilian University, where I developed a Bayesian imaging algorithm for combining different measurement methods in the radio regime, I joined Simona Vegetti's group at the Max Planck Institute for Astrophysics in Garching. My current work focuses on the use of galaxy clusters as cosmic telescopes to study the detailed properties of high-redshift galaxies. Here I am primarily interested in finding an efficient description of the underlying inference problem.

My research focuses on radio/mm/sub-mm interferometric imaging of gravitational lenses. The interplay between AGN and star formation is thought to be important to understand how galaxies evolve. By studying gravitationally lensed galaxies with telescopes such as the Atacama Large sub-Millimetre Array (ALMA) we can resolve structures in distant galaxies at the peak of cosmic star formation and black hole accretion, which can help understand this interplay. The high-resolution data we can obtain with interferometry can also be useful to investigate small-scale mass structures in the lens, which can help us test models for dark matter.

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