Description du sujet de thèse

Probing the interstellar ice composition at dense cloud edges: combining JWST observations with chemical modelling

Stars and planets, including those of our solar system, form from interstellar matter, a mixture of gas and tiny grains of dust. These grains play a key role in the formation of complex molecules, some of which are known as prebiotic. To understand the physical and chemical processes at the origin of these molecules, it is essential to observe the composition of these grains using telescopes, and to simulate their evolution using numerical models. This research project combines these two approaches - astrophysics and chemistry - using state-of-the-art tools, notably infrared observations from the James Webb Space Telescope (JWST), which are revolutionising our understanding of the interstellar medium. Identifying the composition of interstellar grains right from the formation of the first molecules is an essential step in tracing the history of the solar system and the conditions that enabled the emergence of life on Earth.

The PIIM laboratory in Marseille is collaborating with the LAB laboratory in Bordeaux in the context of the international Cheerio observational programme on the James Webb Space Telescope. This project aims to 1) analyse existing NIRCam observations of ices in the Chamaeleon I cloud and 2) understand the gas and solid phase chemistry leading to ice formation in dark clouds in the interstellar medium. The person recruited will work principally on observational extraction and analysis of photometric and spectroscopic data for the Cheerio programme, as well as on interpreting the results of chemical models simulating ice formation in the same cloud region.

The work that will be carried out during the PhD includes:
- Data extraction and analysis of JWST observational datasets, including photometry and infrared spectroscopy; comparison of observations with experimental ice spectra and model outputs.
- Evolving the modelling approach based on inputs from the observational data and previous results.
- Determining the chemical composition of ices in the Chamaeleon I cloud edges and interpreting the chemistry that led to these compositions.
- Exchanging results with the wider, international Cheerio team and leading the writing of publications.

A background in astrophysics, physics and/or physical chemistry is required; experience with a programming language like Python for data analysis is necessary. Prior experience with spectroscopy (IR) or chemical modelling is an advantage and knowledge of astrochemistry is appreciated.
Strong written and oral communication skills in English are expected. The ability to work both in a team and autonomously is also required.
At the time of recruitment, a Masters degree in astrophysics, physics, physical chemistry or a closely related field will be required.

Contexte de travail

The PhD student will work within the research teams H2M (Hydrogen, Molecules, Materials) at the PIIM laboratory, and FEMIS (Star formation and the interstellar medium) at LAB, renowned for their expertise in astrochemistry, combining observations (PIIM and LAB) with laboratory astrophysics experiments (PIIM) and gas-grain chemical models (LAB). The PhD student will have access to all the digital tools of the two teams, including analysis software and chemical models, as well as access to proprietary observations from the James Webb Space Telescope (Program PID 4358). The selected candidate will join the Cheerio project team in the PIIM laboratory, but will regularly travel to work with other team members in the LAB in Bordeaux and with international colleagues. Funding is already acquired for travel between institutes and to conferences.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

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