This internship is in the context of the DESI-2 (2029-2035) experiment preparation.
Since the discovery of the acceleration of the expansion of the Universe in 1998, the cosmology community has gathered its efforts around large experiments to provide a physical explanation to it. In the current model (LCDM) this acceleration is explained by a constant dark energy. The latest generation of experiments, known as “Stage IV”, is becoming live this decade, to name a few: DESI (spectroscopy, 2021-2028), Euclid (photometry+spectroscopy, 2023-2029), Rubin/LSST (photometry, 2026-2036), 4MOST (spectroscopy, 2026-2031).
The DESI experiment is using a telescope with 5000 robotic fiber positioners to observe the spectra of tens of millions of galaxies and measure from those their spectroscopic redshift. Cosmological constraints are then derived using clustering analysis of the 3D-positions of the galaxies. DESI has published in Apr. 2025 its latest cosmological results, hinting a possible need for evolving dark energy.
The DESI team is working on the design of the follow-up experiment, DESI-2. DESI-2 will explore the higher-redshift Universe (2 < z < 4, when the Universe was 1.5-3 Gyrs old), thus will be able to tighten constraints on the geometry of the Universe, along with exploring the primordial physics of the Universe. A key step in such an experiment is to select the targets that will be spectroscopically observed. This target selection is done on photometry, i.e. fluxes measured from imaging. DESI-2 will observe two types of tracers at 2 < z < 4, Lyman Alpha Emitters (LAE) and Lyman Break Galaxies (LBG). The DESI team has already gathered a unique spectroscopic dataset on those LAEs and LBGs, and is leading an imaging medium-band survey for the target selection.
The internship will be on the exploration of those LAEs and LBGs. According to the candidate preference, it could either be focused on the photometry or on the spectroscopy. The photometry project would be to investigate target selections of LAEs/LBGs and their properties. Those would be based on the dedicated medium-band imaging survey (IBIS, with the DECam camera) and representative broad-band imaging. The spectroscopy project would be focused on the properties of the LAE/LBG spectra, for instance on how the observing conditions impact the redshift fitting, or on the analysis of recent DESI pilot data, if available.
The internship will allow the student to work with state-of-art photometry / spectroscopy, to develop knowledge on data manipulation and analysis, along with understanding how large surveys are designed.
We are looking for a Master 2 candidate (note that the internship will not lead to a PhD thesis). The internship will be using python coding. Please contact raichoor@in2p3.apc.fr for any further information. Interested students should send a CV and M1/M2 grade reports to raichoor@apc.in2p3.fr and mei@apc.in2p3.fr.