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Merging, outflows, or rotation? Early galaxy evolution in the context of dark matter assembly


What are the fundamental mechanisms of large-scale structure formation and galaxy evolution in the universe? While dark-matter halo collapse dominates on the largest scales, matter assembly becomes non-linear at mass scales of individual galaxies, where baryons play a non-negligible role.

As baryons accumulate near the centre of the dark matter potential through gas infall and merging of dark-matter haloes, they cause hydrodynamic 'feedback', i.e. outflows triggered by intense star-formation ('starburst-driven winds') and by powerful active galactic nuclei (AGN). Each process will influence the large-scale gas dynamics in the galaxy.

To elucidate the relative importance of these mechanisms and their impact on galaxy evolution in the early universe (when structure assembly proceeded most rapidly), we propose to study the spatially resolved emission line gas kinematics and chemical properties in a moderately large sample of galaxies at redshifts z=0.5-1.25. This range corresp onds to look-back times of 5 to 8 Gyr, about half the age of the universe, where the tails of high-redshift and low-redshift galaxy populations overlap.

The German fellow will carry out this project at the Paris-Meudon observatory and within a Franco-Italian-German collaboration with participation of Swedish and US experts, and a novel observational approach: By combining data obtained with the VLT integral-field spectrographs GIRAFFE in the optical and SINFONI in the near-infrared, we will for the first time map the two-dimensional distribution of gas kinematics, metallicity, extinction, star-formation rates, and electron densities in galaxies in the early universe.

We will thus be able to robustly distinguish virialized rotation from galaxy mergers and winds, and test various cosmological models of galaxy formation. Most importantly, we will probe the fundamental structural parameters of dark matter halos as predicted by dark-matter cosmogonies, specifically

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61 avenue de l'Observatoire

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