Description of the thesis topic

The thesis topic is proposed as part of the start of observations of the southern sky by the Vera C. Rubin Observatory, in the summer of 2025. Its large survey, LSST (Legacy Survey of Space and Time, https://rubinobservatory.org/about), will represent after 10 years the largest and deepest data set ever assembled. Among the key topics it will address, the identification of dark energy and matter are one of the most important puzzles in modern cosmology.

Furthermore, stellar trails, structures extended by tidal effects from an original stellar system such as a star cluster or a satellite galaxy, have recently emerged as a promising probe of the dark matter substructures of our galaxy. The thesis work will focus on the observation of known trails and the very likely discovery of new trails in the first year, or even the first two years, of LSST. The candidate will participate in the validation of image reduction, the extraction and understanding of the star catalog, as well as the implementation of methods for extracting stellar streams from these images and catalogs.

The second topic will focus on the validation, optimization, and use of the LePhare photometric distance estimation code (https://lephare.readthedocs.io/en/latest/) on LSST data. This topic overlaps with the first because LePHARE differs from other codes in being able to discriminate between stars and galaxies, as well as provide physical information about these objects.

Since estimating photometric distances is central to almost all of LSST's science, the candidate will gain crucial expertise within one of the flagship observational projects of modern cosmology. This will be combined with participation in the global effort to uncover the nature of dark matter, currently one of the major enigmas in physics.

Work Context

The work will be carried out within the LSST/ZTF group, within the framework of the first data from the Vera C. Rubin Observatory. The candidate will join the international DESC collaboration as well as the Rubin project, as a member supervised by the scientific leader, who is a "builder" member of DESC and Rubin.

The Clermont Auvergne Physics Laboratory (LPCA, https://lpca.in2p3.fr/), located on the Cézeaux campus, is a joint research unit of the University of Clermont Auvergne and the CNRS, whose main supervisor is the National Institute of Nuclear and Particle Physics (IN2P3). Its research interests include theoretical physics, particle physics, cosmology, and physics for health and the environment. It enjoys an excellent reputation, both nationally and internationally.
In particular, the LPCA—through the LSST ZTF team, where the thesis will be conducted—is a founding member of the Rubin project. Its members participate in the international scientific collaborations DESC (https://lsstdesc.org/) and ZTF. The thesis will be conducted within DESC, in close collaboration with colleagues from the DESC Dark Matter working group.

The candidate will thus benefit from an enriching international environment, with opportunities to travel abroad for work meetings or conferences. Locally, they will benefit from a pleasant setting on the Cézeaux campus, accessible by public transport and close to Clermont-Ferrand city center, and excellent working conditions (flexible hours, partial teleworking, etc...)

Constraints and risks

No object