We study the relation between halo concentration and mass (c − M relation) using galaxy catalogs of the Seventh and Eighth Data Releases of the Sloan Digital Sky Survey (SDSS DR7 and DR8). Assuming that the satellite galaxies follow the distribution of dark matter, we derive the halo concentration by fitting the satellite radial profile with a Nararro Frank and White (NFW) format. The derived c − M relation covers a wide halo mass range from 10 to 10 M. We confirm the anti-correlation between the halo mass and concentration as predicted in cosmological simulations. Our results are in good agreement with those derived using galaxy dynamics and gravitational lensing for halos of 10– 10 M, while they are slightly lower for halos of 10– 10 M. This is because blue satellite galaxies are less concentrated, especially in the inner regions. Instead of using all satellite galaxies, red satellites could be better tracers of the underlying dark matter distribution in galaxy groups.
galaxies: halos – galaxies: evolution – galaxies: abundances
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