Abstract
We have then searched for preferential orientations of faint galaxies in the Coma cluster (down I_Vega~-11.5). By applying a deconvolution method to deep u* and I band images of the Coma cluster, we were able to recover orientations down to faint magnitudes. No preferential orientations are found in more than 95% of the cluster, and the brighter the galaxies, the fewer preferential orientations. The minor axes of late type galaxies are radially oriented along a northeast -southwest direction and are oriented north-south in the western X-ray sub- structures. For early type galaxies, in the western regions showing significant preferential orientations, galaxy major axes are oriented perpendicularly to the north-south direction. In the eastern significant region and close to NGC 4889, galaxy major axes also point toward the 2 cluster dominant galaxies. In the southern significant regions, galaxy planes are tangential with respect to the clustercentric direction, except close to (alpha=194.8, delta=27.65) where the orientation is close to -15deg. Part of the orientations of the minor axes of late type galaxies and of the major axes of early type galaxies can be explained by a tidal torque model applied to cosmological filaments and local merging directions. Another part (close to NGC4889) can be accounted for by collimated infalls. For early type galaxies, the (alpha=194.8, delta=27.65) region shows orientations that probably result from processes involving induced star formation.
Highlights
Large-scale structures are one of the major predictions of cosmological models, which reproduce well the observed galaxy filamentary structures and clusters
Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii
Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institute National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii
Summary
Large-scale structures are one of the major predictions of cosmological models, which reproduce well the observed galaxy filamentary structures and clusters (e.g. de Lapparent et al 1986). West 1994; Dubinski 1998), linking the cluster and the central galaxy growth Another prediction of simulations is that the rotation axis of disk galaxies in large scale structures is perpendicular to the minor axis of the surrounding structure Hawley & Peebles 1975) have led to a wide variety of results: some clusters show preferential galaxy orientations (e.g. Kitzbichler et al 2003; Plionis et al 2003; Aryal et al 2007, and references therein), while some others do not (e.g. Bukhari et al 2003; Torlina et al 2007) Even when such alignments are detected, the results are not always similar.
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