DRF: Thesis SL-DRF-17-0387 - instn

DRF: Thesis SL-DRF-17-0387
RESEARCH FIELD
Astrophysics / Corpuscular physics and outer space
TITLE
The physics of giant star-forming regions in primordial galaxies from a synergy of observations and simulations
ABSTRACT
The morphology of star forming galaxies in the distant Universe, at the peak of their activity at redshift z=1-3, is remarkably different from
that of nearby spirals. They have irregular morphologies, often dominated by giant star forming regions, known as star forming clumps.
These clumps reach remarkably large sizes and masses, orders of magnitude larger than molecular clouds and star clusters in our
Galaxy. This peculiarity of high-redshift star-forming galaxies is thought to be driven by their very large gas fractions and strong
turbulence, compared to the local Universe: gas-rich galaxies can become violently unstable and fragment in such giant clumps.
However, despite several years of studies by many groups worldwide, a quantitative understanding of the nature and physical properties
of these clumps is still lacking both from the theoretical and observational point of view. Hotly debated topics of contending remain,
regarding the distribution of clumps masses, star formation rates, sizes, clumps formation rates and lifetime. More importantly, it remains
unknown whether they survive stellar feedback processes, in which case they can drive the growth of galactic bulges and the fueling of
supermassive black holes at the center of galaxies. In numerical simulations, many teams at different institutions reach wildly different
conclusions, mostly related to discrepant implementation for feedback and regulation in the physics of star formation.
We propose a PhD project to explore a state of the art approach to this topic by simultaneously tracking 3 complementary lines of
research:
1) physical characterization of clumps properties from observations, done for the first time with maps of physical parameters (maps of the
stellar mass, maps of the star formation rate distribution), and with stellar mass limited (complete) samples of distant galaxies from HST
data in CANDELS/UDF/FF.
2) systematic comparison with simulated maps from a large number of competing teams in the community with which we have
collaborative relations, in order to obtain objective understanding of consistencies or differences between observations and various
simulation dataset.
3) running suites of very high resolution numerical simulations with an improved modelling of star formation physics, in particular using
adaptive-resolution hydrodynamic codes and “zooming” on the giant star-forming clumps, to get a more predictive modelling of when and
where new stars formed, and how the turbulent interstellar medium reacts to their feedback processes.
These complementary lines will bring a robust understanding of the nature of the giant clumps, the violent instabilities in primordial galactic
disks, and their role in shaping disks, bulges and central black holes. They will also provide a new, independent way to constrain the gas
fraction in galaxies at various epochs, which is another highly debated issue and crucial to constrain theoretical galaxy formation models.
The proposed work will also ideally prepare future developments with the use of JWST, which will image the mass distribution in primordial
galaxies, and their ionized gas content, and comparison to forthcoming ALMA data probing the various gas phases in young galaxies. The
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Institut national des sciences et techniques nucléaires
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detailed understanding of star formation processes in primordial galaxies will also be a strong asset to understand the relics in old stellar
populations of nearby galaxies, in the context of deep morphology surveys and the Legacy science of EUCLID. The proposed thesis will
also employ numerical simulations performed on the largest supercomputers in France (GENCI) and Europe (PRACE).
LOCATION
Institut de recherche sur les lois fondamentales de l'univers
Service d'Astrophysique
Laboratoire de Cosmologie et d'Evolution des Galaxies
Place: Saclay
Start date of the thesis: 01/09/2017
CONTACT PERSON
Emanuele DADDI
CEA
DSM/IRFU/SAp/LCEG
Orme des Merisiers
Email: [email protected]
UNIVERSITY / GRADUATE SCHOOL
Paris-Diderot (Paris 7)
Astronomie et Astrophysique d'Île de France
FIND OUT MORE
http://irfu.cea.fr/SAp
THESIS SUPERVISOR
Frédéric BOURNAUD
CEA
DRF/IRFU/SAp/LCEG
CEA Orme des Merisiers - Bat 709
Commissariat à l'énergie atomique et aux énergies alternatives
Institut national des sciences et techniques nucléaires
www­instn.cea.fr
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