Offre en lien avec l’Action/le Réseau : BigData4Astro/– — –

Laboratoire/Entreprise : Laboratoire d’Etudes Spatiales et d’Instrumentatio
Durée : 36 months
Contact : mickael.bonnefoy@univ-grenoble-alpes.fr
Date limite de publication : 2021-04-01

Contexte :
Since the pioneering discoveries of disks and extrasolar planets in the mid-90’s, a new domain of astrophysics, exo-planetology, has emerged, that aims at exploring the diversity of extrasolar planetary systems, at understanding their formation and evolution, and, at ultimately detecting Earth-like planets. Today, high-contrast adaptive optics-fed imagers searching massive Jupiters beyond 5-10 astronomical units, where true solar system giants reside. The combination with medium- (R=λ/Δλ=1000-10 000) and high- (R=λ/Δλ>10 000) resolution spectrographs is furthermore seen as a key approach to get rid of the speckle noise which hinders the direct imaging and spectroscopic characterization of planets with ground based tele-scopes. It also promises to yield new accurate information on the physical and at-mospheric properties of the planets in particular on the elemental abundances (C/O, N/H, Fe/Si) which appear as promising tracers of the object formation pathway. At such resolutions, molecular absorptions start to be resolved in the planet spectra and can be distinguished from the dominant signal from the host star. Correlation tech-niques are presently used to produce a coherent signal out of the planet spectral signatures and offer to simultaneously enhance the detection (e.g. Birkby et al, 2017) and characterize the objects. The molecular mapping technique (Hoeijmakers et al. 2018; Petrus et al. 2020) apply the cross-correlation techniques to hyperspec-tral data produced by integral-field spectrographs.
A suite of advanced integral field spectrographs equipped with coronographs and fed by performant adaptive optics modules will enter operation in the coming decade (VLT/ERIS, GTC/FRIDA, VLT/MAVIS, ELT/HARMONI & METIS) and overtake the capabilities of present instruments (e.g., VLT/SINFONI, Keck/OSIRIS). This motivates further the exploration of the diversity contained in medium- and high- resolution spectroscopic data to improve the performance capabilities and to extract properly the spectroscopic informations of the planet and characterize their physical and atmospheric properties.

Sujet :
The student will develop innovative methods to exploit the data diversity contained in medium- and high-resolution spectrographs (classical and integral field) to boost the detection capabilities of the instruments and retrieve quantitative information on the planet properties. The student will characterize the atmospheres of giant planets already
known and those detected in the course of our survey as part of the COBREX ERC project. For each planet, the physical characteristics (effective temperature, surface gravity, pressure-temperature profiles), and the composition will be derived. The possibility of intervening dust (circumstellar or circumplanetary) will be considered. Comparative studies between the various planets will be made.
The PhD will lead the development and validation of new algorithms applicable to integral field spectrograph at medium-resolving power and high-spectral resolution to improve the detection and characterization of giant planets (e.g., Petrus et al. 2020).
She/He will develop and test new approaches for inverting exoplanet spectra at medium and high spectral resolutions and measure the chemical abundances of the objects and constrain their atmospheric properties (cloud properties, bulk composition, temperature-pressure profiles-. This work will rely on the use of grids of synthetic spectra computed from atmospheric model (Charnay et al. 2018). She/He will couple these inversion methods to the detection algorithms in a single tool capable of both detecting and characterizing any object simultaneously.
The student will have access to data from cutting-edge integral field (Keck/OSIRIS, VLT/SINFONI, Gemini/NIFS) and high-resolution spectrographs (CFHT/SPIRou, ESO/NIRPS, CRIRES+). He/She will exploit a new high-contrast mode of the ERIS integral field spectrograph (ERIS+) to be installed on the VLT and evaluate the benefit and limitation of that mode based on observed and simulated data.

The first year of the PhD will be held at IPAG (Grenoble) where the data will be analyzed. The last two years will be held at LESIA, Observatoire de Paris.
The PhD will participate to observations to complete the available, archival data, in particular with ESO’s telescopes and with JWST.

Profil du candidat :
As a member of the ERC project COBREX, the student will be part of a lively team with expertises in exoplanetary systems (planets, disks), high contrast imaging, radial velocity, and astrometry. The student will also interact with experts of machine learning from the INRIA in Paris and GIPSA-Lab in Grenoble. Several PhD positions are opened as part of the project and can be found here:
*https://bit.ly/3i8p71l
*https://bit.ly/3oF8Hjk
*https://bit.ly/3icTnYK
*https://bit.ly/3sBoeTO

The student should be highly motivated and able to propose and deal with complex mathematical concepts. We are therefore looking for a student with a strong background in data science and applied mathematics and could provide him or her with the necessary informations on the astrophysical context related to her/his research topic.

The applicant should have a good level of written and spoken English.

Team work ability is essential.

Formation et compétences requises :
The applicant should have a Master’s degree in Computer Science, Physics, or Astrophysics and advanced skills in data analysis/signal processing.

Knowledge of Python and associated key librairies (scipy, numpy, pandas, scikit-learn, keras, tensorflow) will be highly appreciated. Knowledge of the Julia langage is a plus.

Adresse d’emploi :
LESIA
Observatoire de Paris, Section de Meudon
5, place Jules Janssen
92195 MEUDON Cedex

IPAG
414 Rue de la Piscine
38400 SAINT-MARTIN D’HERES