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Séminaire : Simulations of the Reionization

Date: 
Jeudi, 2 Avril, 2015 - 11:00
Lieu: 
IAS, bât 121, salle 1-2-3
Nom de l'intervenant: 
Dominique Aubert (Obs. de Strasbourg)

 

The Reionization designates the epoch where the first sources appeared in the history of the Universe. These sources (mostly stars) emerged roughly 300 millions years after the Big Bang and produced a ultraviolet radiation that led to an almost fully ionized Universe by z~6, 1 billion years after the Big-Bang.

 

During the same epoch, the first stages of the galaxy formation process took place and it is believed that the current properties of galaxies (and the Milky Way among them) still bear the marks of the Reionization that took place more than 12 billions years ago. 

 

The existence of such a transition is now firmly established (via e.g. the study of the CMB or the spectra of distant quasars) and the
next decade will provide us with an unprecedented view of the these ages with facilities such as JWST or SKA. Overall, this transition results from the growth of large scale structures, the formation of the first galaxies/stars and the physics of matter-radiation interaction and is therefore extremely rich in terms of physical couplings.

For this reasons a great effort is put to model the Reionization process, especially through the use of cosmological simulations that
combine cosmology, gravitational/gas dynamics and radiative transfer. These simulations must be able to track simultaneously the cosmological scales and the close environment of the primeval sources, leading to computations that involve great numbers of computing cores and resolution elements.

 

For a few years, we have been developing such cosmological codes in Strasbourg to investigate the physics at play during the reionization, with an emphasis on the usage of graphics processing units (or GPUs) that provide orders of magnitude accelerations to our tools.

 

I will present these new codes and how we took advantage of supercomputing facilities (such as Curie-CCRT with >200 GPUs and Titan-ORNL >8000 GPUs) for our studies. I will also discuss the results we obtained on the geometrical evolution of the Reionization process on its largest scales and on its potential impact on the formation of the Milky Way.

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