We perform a morphological study of 124 spectroscopically confirmed cluster galaxies in the z=0.84 galaxy cluster RX J0152.7-1357. Our classification scheme includes color information, visual morphology, and 1-component and 2-component light profile
fitting derived from Hubble Space Telescope riz imaging. We adopt a modified version of a detailed classification scheme previously used in studies of field galaxies and found to be correlated with kinematic features of those galaxies. We compare our cluster galaxy morphologies to those of field galaxies at similar redshift. We also compare galaxy morphologies in regions of the cluster with different dark-matter density as determined by weak-lensing maps. We find an early-type fraction for the cluster population as a whole of 47%, about 2.8 times higher than the field, and similar to the dynamically young cluster MS 1054 at similar redshift. We find the most drastic change in morphology distribution between the low and intermediate dark matter density regions within the cluster, with the early type fraction doubling and the peculiar fraction dropping by nearly half. The peculiar fraction drops more drastically than the spiral fraction going from the outskirts to the intermediate-density regions. This suggests that many galaxies falling into clusters at z~0.8 may evolve directly from peculiar, merging, and compact systems into early-type galaxies, without having the chance to first evolve into a regular spiral galaxy.
Using the deepest and most complete observations of distant galaxies, we investigate the progenitors of present-day large spirals. Observations include spatially-resolved kinematics, detailed morphologies and photometry from UV to mid-IR. Six billion
s years ago, half of the present-day spirals were starbursts experiencing major mergers, evidenced by their anomalous kinematics and morphologies. They are consequently modeled using hydrodynamics models of mergers and it perfectly matches with merger rate predictions by state-of-the-art-{Lambda}CDM semi-empirical models. Furthermore imprints in the halo of local galaxies such as M31 or NGC5907 are likely caused by major merger relics. This suggests that the hierarchical scenario has played a major role in shaping the massive galaxies of the Hubble sequence. Linking galaxy properties at different epochs is the best way to fully understand galaxy formation processes and we have tested such a link through generated series of simulations of gas-rich mergers. Mergers have expelled material in galactic haloes and beyond, possibly explaining 60% of the missing baryons in Milky-Way (MW) mass galaxies. A past major merger in M31 might affect drastically our understanding of Local Group galaxies, including MW dwarves. We also propose future directions to observationally constrain the necessary ingredients in galaxy simulations.
At intermediate redshifts, many galaxies seem to be perturbed or suffering from an interaction. Considering that disk galaxies may have formed and evolved through minor mergers or through major mergers, it is important to understand the mechanisms at
play during each type of merger in order to be able to establish the outcome of such an event. In some cases, only the use of both morphological and kinematical information can disentangle the actual configuration of an encounter at intermediate redshift. In this work, we present the morphological and kinematical analysis of a system at z=0.74 in order to understand its configuration, interacting stage and evolution. Using the integral field spectrograph GIRAFFE, long-slit spectroscopy by FORS2 and direct optical images from the HST-ACS and ISAAC near-infrared images, we disentangle the morphology of this system, its star-formation history and its extended kinematics in order to propose a possible configuration for the system. Numerical simulations are used to test different interacting scenarii. We identify this system as a face-on disk galaxy with a very bright bar in interaction with a smaller companion with a mass ratio of 3:1. The relevance of kinematical information and the constraints it imposes on the interpretation of the observations of distant galaxies is particularly strengthened in this case. This object is amongst the best example on how one may misinterpret morphology in the absence of kinematical information.
