PhD position on Cosmology (M/F)

EURAXESS Ireland; Orsay; Sur place; EUR 18 972 - 23 436; Plein temps

Résumé du poste

IJCLab invites a PhD student to work on extracting the kinetic Sunyaev–Zeldovich (kSZ) signal from the CMB power spectrum using data from the Simons Observatory. The project involves modeling the local and reionization kSZ components to derive robust cosmological constraints and will be supervised by Thibaut Louis, with co-supervision by Léo Vacher.

The work is based in the CMB team at IJCLab and includes strong international collaboration with Berkeley researchers.

Qualifications

• Candidate is expected to be enrolled in a PhD program in physics/astrophysics.
• Experience with data analysis of cosmological signals is a plus.
• Good collaboration and communication skills are required.

Responsabilités

• Analyze Simons Observatory data to extract the kinetic SZ contribution to the CMB power spectrum.
• Model local and reionization kSZ components to derive cosmological constraints.
• Collaborate with international teams, particularly with Berkeley researchers, and contribute to publications.

Connaissances

Python

Data analysis

CMB astronomy

Collaborative research

Formation

PhD in physics or astrophysics

Outils

Python (NumPy/SciPy)

Matplotlib

Description du poste

Offer Description

The Irène Joliot-Curie Physics Laboratory of 2 Infinities (IJCLab) is a UMR under the supervision of the CNRS (IN2P3), the University of Paris-Saclay and the University of Paris is located on the campus of the University of Paris -Saclay in Orsay. The laboratory is located on the campus of the Université Paris-Sud, Université Paris-Saclay in Orsay. The campus is located 20 km south of Paris and easily accessible by RER in 35 minutes.
The staff is made up of nearly 560 permanent (340 engineers, technicians and administrators and 220 researchers and teacher-researchers) and approximately 200 non-permanent including 120 doctoral students. The research themes of the laboratory are nuclear physics, high energy physics, theoretical physics, astroparticles, astrophysics and cosmology, particle accelerators, energy and the environment and health. IJCLab has very significant technical capacities (around 280 IT) in all the major fields required to design, develop / implement the experimental devices necessary for its scientific activity, as well as the design, development and use of instruments.
The year 2026 will mark the start of the first observing campaign of the cosmic microwave background (CMB) with the Simons Observatory Large Aperture Telescope. Equipped with a 6-metre primary mirror and around 60,000 detectors, more than all the detectors that have observed the CMB to date combined, this instrument represents a major advance for observational cosmology.
This telescope will make it possible to obtain new constraints on the parameters of the standard cosmological model and to test possible extensions to it. Achieving these goals will require extremely precise control of instrumental systematic effects, as well as comprehensive modelling of the astrophysical signals that are superimposed on the cosmological signal.
One of these signals arises from the interaction between photons from the cosmic microwave background and free electrons present in the Universe. This interaction, known as the Sunyaev-Zeldovich (SZ) effect, appears in two main forms: the thermal SZ effect, caused by the thermal motion of electrons within galaxy clusters, and the kinetic SZ effect (kSZ), which results from the bulk motion of ionized gas. Characterizing the kSZ effect is now a major goal in cosmology, because it provides information both on the velocity fields of the recent Universe, and therefore on gravity on large scales, and on the epoch of reionization, during which the first luminous sources ionized the intergalactic gas, forming bubbles that gradually expanded and then connected.

IJCLab bases its recruitment policy on the promotion of equality, diversity, and inclusion.

The student will use data from the Simons Observatory to extract the kinetic Sunyaev-Zeldovich contribution from the CMB power spectrum. This contribution will then be modelled as two distinct components: the local kSZ signal, associated with the recent Universe, and the reionization kSZ signal, with the aim of deriving robust cosmological constraints on this little‑known phase of the Universe, when it was around 500 million years old.
The PhD will be supervised by Thibaut Louis, co‑lead of the data analysis for the Simons Observatory Large Aperture Telescope, and co‑supervised by Léo Vacher, co‑lead of the characterization of astrophysical emissions. Based within the CMB team at IJCLab, the project will have a strong international dimension and will benefit in particular from close scientific collaboration with James Bartlett and Simone Ferraro, both at the University of Berkeley, who are specialists in the measurement and modelling of Sunyaev–Zeldovich effects. The complementarity between the data‑analysis expertise at IJCLab and Berkeley's expertise in SZ‑effect modelling and galaxy observations will make it possible to robustly separate the local kSZ signal from the signal associated with reionization, a crucial step in achieving the scientific goals of the PhD. Interactions with the Berkeley team will be supported and facilitated by the IRL Centre Pierre Binétruy.