Precision photometry of the LSST survey with GAIA for type Ia supernova cosmology

Stage numéro : M2-1819-RE-01
Laboratoire :Centre de Physique des Particules de Marseille Case 902
 163 avenue de Luminy - 13288 Marseille Cedex 9
Directeur :Cristinel Diaconu - -
Correspondant :William Gillard - -
Groupe d'accueil :Renoir
Chef de groupe :Dominique Fouchez - -
Responsable de stage :Fabrice Feinstein - 04 91 82 72 16 / +33 6 31 78 84 79 -

Thématique : Cosmologie observationnelle

The acceleration of the expansion of the Universe was discovered twenty years ago, thanks to the use of type Ia supernovae (SN Ia) as standard candles. The constituent responsible for this acceleration, which accounts for 68 percent of the density of the Universe, has been called dark energy. This phenomenon, which dominates the dynamics of expansion, remains enigmatic.

The future Large Synoptic Survey Telescope (LSST) will revolutionize our knowledge of cosmology. It will observe several tens of thousands of SN Ia under optimal conditions of a precision photometry instrument on the Chile sky. These observations will allow to construct a Hubble diagram with a statistic of SN Ia 20 to 100 times higher than that of the current diagrams which contain 700 of them. To make the most of this statistic, it is necessary to obtain per-mil photometric precision, to limit the bias in determining the luminous distance of SN Ia and of their host galaxy.

Presently, hundreds of millions of stable stars are precisely measured by the GAIA satellite. At CPPM, we develop a method based on a global fit on all these stars in order to correct for instrument and atmosphere variations.

It involves manipulating (1G x 100M) size matrices with modern sparse matrix techniques. The CPPM hosts a modern HPC (800 cores, 500 GB to 1500 GB of RAM) that is availlable for the internship. During the internship, we will refine the method, and test performances on simulation.

The per-mil precision goal has never been achieved previously. This will allow a characterisation of the dark energy with unprecedented precision.

This work is done in collaboration with SLAC/Stanford colleagues.

Following the Master 2 internship, a thesis (2019-2022) is proposed on this topic. It is subject to be funded by the local doctoral school.