Dr. Guillaume Mahler - Astrophysicist

Me in a nutshell

My name is Guillaume Mahler (He/Him). I am an active researcher in astrophysics since 2017. I am now a researcher and teacher at the Univeristy of Liège since October 2023.  Over there I am trying to uncovered the true nature of Dark Matter. I am devolloping original statistical tools combined with observations of galaxy clusters with Hubble Space Telescope, Euclid, the JWST and the spectrograph MUSE. I am also interested in the resolved properties of highly magnified galaxies and the epoch of reionisation and I like to "unlensed" them to get a better understanding of their morphology. 

During my Ph. D. I built detailed map of the dark matter within clusters of galaxies. this involved a lot of physically motivated modeling.  After my Ph. D. I moved to the U.S.A as a postdoc at the University of Michigan. These two years allowed me to improve on my english skills, get more involved in managing students and advancing several projects at the same time as well as give talks in front of international audiences. In october 2020 I was awarded an individual Marie-Curie fellowship at Durham university (U.K), where I spent 3 years working on galaxy clusters and the dark matter within them.


Keywords: Minimization procedure / Data analysis / Image processing / Numercial calculations.

NEWS

Recent publication:

Check on the web page we built for it - here

What do I do?

I would say I have two main areas of science focus.

On one side, I am using what we people call gravitational lensing to study dark matter. Our current models say that dark matter is about 70% of the mass content of our universe but we've never seen it. A lot of experience have tried, either on Earth (e.g. Icecube to only cite one)  but so far it remains a non-detection. One way to find it is to observe where it is dominant, clusters of galaxies for example, and that's what I am doing. I observe clusters with either Hubble Space Telescope (and soon JWST) as well as the spectrograph MUSE to model the dark matter content of galaxy clusters. That modelling allows me to lean on the distribution of mass among the different components of the cluster and also the overall shape of it

On the other side, I am using gravitational lensing to study the background lensed galaxies. It is super helpful because lensed galaxies gain in luminosity and possibly resolution by being stretched so much. Since lensing is achromatic (the effect is not different no matter the wavelength you are looking at it) one can study it in a lot of different wavelengths. I mainly focus on the rest-frame UV and study star formation and ionising emission of these galaxies.

What is gravitational lensing?

Gravitational lensing is the apparent bending of the light path from a source behind a massive object aligned in the line of sight. Many people explained it so much better than I would do it so here are a few links and videos of the phenomenon that I found useful

https://hubblesite.org/contents/articles/gravitational-lensing (simple and pretty explanation)

https://supernova.eso.org/exhibition/videos/heic1106a/ (a nice video of it)

https://www.ita.uni-heidelberg.de/~jmerten/misc/meneghetti_lensing.pdf (The nitty-gritty details - only for experts)