Issue |
A&A
Volume 493, Number 2, January II 2009
|
|
---|---|---|
Page(s) | 399 - 407 | |
Section | Cosmology (including clusters of galaxies) | |
DOI | https://doi.org/10.1051/0004-6361:200810535 | |
Published online | 06 November 2008 |
Orientations of very faint galaxies in the Coma cluster*
1
LAM, Pôle de l'Étoile Site de Château-Gombert, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France e-mail: christophe.adami@oamp.fr
2
Institut d'Astrophysique de Paris, CNRS, UMR 7095, Université Pierre et Marie Curie, 98bis Bd Arago, 75014 Paris, France
3
Canada-France-Hawaii Telescope Corporation, Kamuela, HI 96743, USA
4
Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 Av. Edouard Belin, 31400 Toulouse, France
5
Department of Physics and Astronomy, Northwestern University, 2131 Sheridan Road, Evanston IL 60208-2900, USA
Received:
7
July
2008
Accepted:
2
October
2008
Context. Models of large scale structure formation predict the existence of preferential orientations for galaxies in clusters.
Aims. We have searched for preferential orientations of very faint galaxies
in the Coma cluster (down ).
Methods. By applying a deconvolution method to deep u* and I band images of the Coma cluster, we were able to recover orientations down to very faint magnitudes, close to the faintest dwarf galaxies in the Coma cluster.
Results. No preferential orientations are found in more than 95% of the
cluster area, and the brighter the galaxies, the fewer preferential
orientations we detect. The minor axes of late type galaxies are
radially oriented along a northeast-southwest direction and are
oriented in a north-south direction in the western X-ray
substructures. For early type galaxies in the western
regions showing significant preferential orientations, galaxy major axes
tend to be oriented perpendicularly to the
north-south direction. In the eastern significant region and close to
NGC 4889, galaxy major axes also tend to point toward the two cluster
dominant galaxies. In the southern significant regions, galaxy planes
tend to be tangential with respect to the clustercentric direction,
except close to (,
) where the orientation is
close to -15 deg. Early and late type galaxies do not have the same
behaviour regarding orientation.
Conclusions. Considering various models, we give an interpretation
which can account for the existence of preferential orientations for
galaxies (e.g. the tidal torque model or interactions with the intra
cluster medium). 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 the tidal torque model applied both to cosmological filaments and
local merging directions. Another part (close to NGC 4889) can be
accounted for by collimated infalls. For early type galaxies, an
additional region () shows orientations
that probably result from local processes involving induced star
formation.
Key words: galaxies: clusters: individual: Coma
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. This work is also partly based on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. 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.
© ESO, 2009
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