Environment effects on galactical and extra-galactical stellar systems: a numerical and observational study.

Details Environment effects on galactical and extra-galactical stellar systems: a numerical and observational study. Environment effects on galactical and extra-galactical stellar systems: a numerical and observational study.

Sep 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998phdt.......217l&link_type=abstract

PhD Thesis, University Paris 7, 1998.

Mathematics

Logic

1

Scientific paper

This thesis work is dealing in a first part with the influence of our Galaxy on its globular cluster population. First we simulated the gravitational shocks felt by a globular cluster during the crossing of the galactic plane (<>). We adapted a code from F. Leeuwin which is devoted to probe very weak perturbations on a stellar system at the equilibrium. It has been possible to describe the transient effects of the disk shocking on the globular cluster structure. It appears that the adiabatic component of the stellar system, defined by Weinberg (1994a), contributes to an important part for the heating of the cluster during the crossing. Some observational tests are proposed to measure these disk shocking effects on the globular cluster. We observed 6 globular clusters in the CO(1 to 0) transition at 115 GHz with the IRAM 30-m telescope (Granada) : it is shown that the disk crossing and the hot gaseous halo are very efficient in the stripping of the molecular gas in the globular clusters, released by the mass loss of the giant stars. The internal dynamics of globular clusters and the influence of the Galaxy lead to a mass loss in these stellar systems varying with time. We performed N-body simulations to study this mass loss in the galactic potential well and enlight various physical processes (rotation, gravitational shocks, mass segregation). A program of wide field study has been conducted on 20 globular clusters from photographic films and plates digitalized at the <> (CAI). In order to detect the tidal tails of globular cluster, we used a star-counting technique from a source-extracted catalogue. These stars are selected in the color-magnitude diagram. A wavelet transform is then applied on the star-count because it is particularly suited for different scale structure analysis. It has been found around the clusters large tidal structures revealing their dynamical story in the Galaxy. In one case (NGC 5139) it has been possible to estimate the mass loss of this cluster during the disk shocking. We have been able to observe similar tidal effects in open clusters. The same technique has been applied on CCD observations of isolated and binary clusters in the western part of the LMC bar. We confirmed their physical binarity through the interactions disclosed by these observations. Combined with the age determination of the clusters, these observations lead to the problem of their formation and survival (<>) : we proposed a formation scenario based on the tidal interactions SMC-LMC which created groups of star clusters, enhancing the tidal capture cross section. We give an estimate of the tidal tail mass in these systems and of the total mass of two clusters. We looked for tidal effects in globular clusters of M31 and of the FORNAX dwarf spheroidal galaxy. For various reasons it has not been possible to show clearly the interaction of these clusters with their host galaxy. The second part of this thesis work is dealing with galaxies. First we have observed 70 galaxies belonging to 45 Hickson compact groups in the CO(1 to 0) and CO(2 to 1) lines, in order to determine their molecular content. These observations were carried out with the 30 meter radiotelescope of the Instituto de Radio Astronomia Millimetrica (IRAM). We studied the group influence on the molecular content of galaxies with respect to a control sample, including various environments and morphological types. The molecular gas content in compact group galaxies is similar to that in pairs and starburst samples through a Kolmogorov-Smirnov and \chitwo\ statistical analysis. But the estimate of the completeness distribution is moderating somehow this latter result. Nevertheless the most compact configurations appear to have an enhanced htwo\ content. We have observed, as well, a double-barred galaxie, namely NGC 5850, in the CO(1 to 0) and CO(2 to 1) lines using the IRAM-30m and interferometer telescopes. The first results of dynamical models and molecular gas are presented.

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