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DRF : Sujet de thèse SL-DRF-18-0255

INTITULÉ DU SUJET Français English

JWST: from data analysis software and techniques to the quest for hidden mergers in high redshift galaxies


WST will be launched early in 2019, with an important participation from ESA, CNES and CEA for the mid-infrared instrument MIRI. JWST capabilities are revolutionary, compared to the existing state of the art, in terms of resolution and sensitivity over the 1- 30?m wavelength range, where stars and (warm) dust emit their light from galaxies at high redshift. For the first time JWST will provide spatially resolved photometry up to the mid-IR (at least 10?m, with NIRCAM and MIRI) with sub-arcsec resolution. The competitive exploitation of the data for scientific endeavors will require the mastering of the data, deeply understanding the reduction, treatment and developing tools to foster the analysis. I propose a PhD thesis in Saclay as a collaborative effort between experts from 'MICE, the Centre of Expertise for MIRI', developed at CEA/Irfu/DAp, and with researchers in galaxy formation and evolution. The student will be responsible for developing new high level software for the analysis of resolved imaging data from MIRI and NIRCAM, modeling and understand the resolution, 'pixelization' and PSF convolution effects. This will include high-level software to create spatially resolved maps of physical parameters (stellar mass, dust attenuation, stellar age, star formation rate) and pixel-by-pixel spectral energy distributions. The student will work on testing and improving the existing MIRI simulator, adapting it to the case of resolved observations of distant galaxies. The results of the efforts will be shared with several of the CEA Saclay groups in the spirit of fostering our expertise and efficiency in the early use of the groundbreaking JWST data. This work will be based on data from our recently approved Early Release Science (ERS) project observing with a suite of JWST instruments (NIRCAM, NIRSPEC, and MIRI) on well-studied cosmological fields. This ERS project is lead by S. Finkelstein at the University of Texas and includes E. Daddi and D. Elbaz from CEA-Saclay among the international teams of proposers. These observations will be among the first delivered by JWST, in parallel with those from GTO teams.

The student will ultimately use the Early Release Science data on cosmological fields to search for ongoing hidden merger events and AGN components resolved inside galaxies, by distinguishing them from the whole galaxy (e.g., nuclear events, or similar). These are lower luminosities and therefore much more frequent events, which affect only a subset of the galaxy, while the rest behaves as a normal disk, similar to M82 that could be a local proto-type of this situation. This research is based on recent discoveries from our team at the peak of galaxy formation z=1-4, including ALMA high resolution observations of distant star forming galaxies showing compact dust embedded cores (Cibinel, Daddi, Bournaud et al 2017), near-IR rest frame line spectroscopy of distant starbursts showing optically thick cores with growing AGNs (Calabro, Daddi et al in preparation), and other ongoing works. Eventually this research will lead to the first realistic estimate of the impact of mergers on star formation in the distant Universe, a widely discussed and hot topic. Also, we could shed new lights on the issues of black hole growth duty cycle and the role of feedback in terminating star formation at high redshifts.


Master Astrophysique

Institut de recherche sur les lois fondamentales de l'univers
Service d'Astrophysique
Laboratoire de Cosmologie et d'Evolution des Galaxies
Centre : Saclay
Date souhaitée pour le début de la thèse : 01/10/2018

Emanuele DADDI  

Orme des Merisiers

Paris-Diderot (Paris 7)
Astronomie et Astrophysique d'Île de France

Emanuele DADDI

Orme des Merisiers