Other
Scientific paper
Jan 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21533002s&link_type=abstract
American Astronomical Society, AAS Meeting #215, #330.02; Bulletin of the American Astronomical Society, Vol. 42, p.428
Other
1
Scientific paper
According to the current paradigm of galaxy formation, all galaxies form as a result of gas cooling at the center of the potential well of dark matter halos. When a halo and its 'central' galaxy is accreted by a larger halo, it becomes a subhalo and its galaxy becomes a 'satellite' galaxy. We test two related assumptions in this paradigm. Firstly, the central galaxy in a halo is expected to be the most luminous and most massive galaxy in a halo, because it continues to accrete gas and grow while satellites merge into it. Secondly, the brightest galaxy in a virialized halo is expected to reside at rest at the center of the potential well. We use the halo-based galaxy group catalog extracted from the Sloan Digital Sky Survey, and we compare it to mock group catalogs with SDSS-like properties. We analyze the distributions of two parameters: the difference between the line-of-sight velocity of the brightest halo galaxy and the mean velocity of the other group members, as well as the projected separation between the brightest halo galaxy and the mean position of the other galaxies. Our analyses of the velocities and positions of group galaxies imply that both of the assumptions are false. In particular, we find that the dominant effect is that in a large fraction of halos the brightest galaxy is not the central galaxy. We also quantify the degree to which central galaxies are offset and moving with respect to the halo center, although this is a weaker effect. These results have important implications for galaxy formation models.
Fontanot Fabio
Mo Houjun
More Surhud
Skibba Ramin A.
van den Bosch Frank
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