Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2010-05-11
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
MNRAS in press (10 pages, 10 figures)
Scientific paper
We use dark matter haloes identified in the MareNostrum Universe and galaxy groups identified in the Sloan Data Release 7 galaxy catalogue, to study the relation between halo shape and halo dynamics, parametrizing out the mass of the systems. A strong shape-dynamics, independent of mass, correlation is present in the simulation data, which we find it to be due to different halo formation times. Early formation time haloes are, at the present epoch, more spherical and have higher velocity dispersions than late forming-time haloes. The halo shape-dynamics correlation, albeit weaker, survives the projection in 2D (ie., among projected shape and 1-D velocity dispersion). A similar shape-dynamics correlation, independent of mass, is also found in the SDSS DR7 groups of galaxies and in order to investigate its cause we have tested and used, as a proxy of the group formation time, a concentration parameter. We have found, as in the case of the simulated haloes, that less concentrated groups, corresponding to late formation times, have lower velocity dispersions and higher elongations than groups with higher values of concentration, corresponding to early formation times.
Gottlöber Stefan
Merchán Manuel
Plionis Manolis
Ragone-Figueroa Cinthia
Yepes Gustavo
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