4 Comparison of corresponding properties

In the previous section we presented the properties of the different components of NGC 1399 and the galaxy population in the center of the cluster. In Fig. 2 we give a schematic overview of the surface density/brightness (SD/SB) profiles of the different components and their extension. The profiles are arbitrarily shifted in the ordinate axis. The surface densities of GCs and galaxies are number densities, whereas the profile of the galaxy light is a surface brightness profile. Nevertheless, this is comparable to the number density profile, if one assumes similar stellar populations and, accordingly, similar M/L_V ratios. The surface density of the X-ray gas is again a particle (number) density, $n_{\rm gas} \propto r^{\gamma}$. The gas density profile is derived from the surface brightness distribution of the X-ray gas $S(r) \propto r^{\tau}$ under the assumption of isothermal conditions ($\tau = (\gamma+1)/2$) for a radius larger than about 10 kpc (Jones et al. 1997).

The plot shows that the profile slopes of the blue GC population and the cD halo light are strikingly similar, whereas the distribution of dE/dS0 galaxies is somewhat flatter in the central $0\hbox{$.\!\!^\circ$}7$ and slightly steeper outside. Interestingly, the surface density profile of the X-ray gas is also very similar in slope and extension to the cD halo light and the blue GCs. In contrast, the profile of the bulge light of NGC 1399 is significantly steeper than all other profiles.

The same behaviour can be seen in the velocity dispersion. It is comparable for dwarf galaxies and GCS, whereas the stars in the stellar bulge have a lower $\sigma_v$ (see also Minniti et al. 1998; Kissler-Patig et al. 1999). This agreement in morphological and dynamical properties of GCs, the cD halo light, and perhaps also the gas particles might suggest that these components share a common history (or origin). In the next section we describe some scenarios that might have happened when dwarf galaxies interacted with the central cluster galaxy.