Congratulations to Dr. Thibault Kuntzer for obtaining his PhD
© 2018 EPFL
Thibault Kuntzer of EPFL's Laboratory of Astrophysics was awarded a PhD in January 2018 for his thesis: "Machine-learning methods for weak lensing analysis of the ESA Euclid sky survey".
Dark matter and dark energy are the two biggest mysteries of current cosmology. The European Space Agency satellite Euclid will be cosmological mission to probe the nature the dark components of the Universe. It will image with unprecedented details 1.5 billion galaxies, or about 1% of all of the observable galaxies.
Photons follow the shortest path. In the general relativity framework, this path is distorted by the mass distribution. This is the known as gravitational lensing. The light profiles of distant galaxies get slightly sheared by the mass distribution. Galaxy shapes are affected by weak lensing. Cosmological information is contained in the shear. Retrieving the shear leads to constraining cosmological models.
During his PhD thesis, Dr Kuntzer worked on several aspects of shear measurement. Shear measurement requires an exquisite determination of the telescope observation kernel, known as the PSF. He studied PSF reconstruction biases induced by unresolved binary stars and designed mitigation schemes. He worked on a novel and fast spectral classification of stars, a key step to accurately measure the shear, requiring much less information than other techniques and proposed a PSF reconstruction scheme using advanced machine-learning techniques. When the PSF is well understood, the shear measurement can take place. Dr Kuntzer introduced machine learning to measure the shear reaching state-of-the-art results. Finally, he contributed to the development of tools that detect rare manifestations of the strong lensing regime.