Séminaire Lagrange - Myriam Rodrigues - GEPI/OBSPM


mardi 31 janvier 2017, 10h30, NEF - Mont Gros - CION - séminaire en anglais - retransmis à Valrose


Myriam Rodrigues - GEPI/OBSPM

Unveil the process responsible for the mass grow and acquisition of the angular momentum of spiral galaxies is one of the most long-standing problems of galaxy formation. Two concurrent scenarios have emerged to explain the formation of disc galaxies: in-situ smooth gas accretion from cosmological filaments, as opposed to a merger-driven scenario. A crucial test to refute either one of these two scenarios requires to estimate the fraction of isolated disks together with that of galaxies involved in a merger sequence in the distant Universe. Since 2014, the near-infrared multi-IFU spectrographs KMOS has collected kinematics observations for hundreds of distant galaxies. From these kinematic observations, several studies have estimated the fraction of distant disk by identifying objects having kinematics patterns compatible with a rotation. However, rotation can be also induced by orbital motions in a merger sequence. A multi-criteria approach is thus required to identify mergers in all phases from first passage to post-coalescence. I will present a morpho-kinematic classification that considers additional indicators such as the morphology to further identify virialized spirals. We applied this classification scheme to a representative sample of intermediate-mass galaxies at z~1, observed by the kinematic survey KMOS3D. The robustness of the morpho-kinematic classification for disentangling isolated disks from mergers have been tested with an analysis of pairs from the open-grism redshift survey 3D-HST. Our results show that only one third of z~1 galaxies are isolated and virialized spirals, while 58% of them are likely involved in a merger sequence, from first approach to disk rebuilding. The later fraction is in good agreement with the results of semi-empirical ΛCDM models, supporting a merger-dominated hierarchical scenario as being the main driver to shape spiral galaxies at least during the last 8 billion years

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