| Abstract : | The dark matter halo surface density, given by the product of the dark matter core radius (rc ) and core density (ρc ) has been shown to be a constant for a wide range of isolated galaxy systems. Here, we carry out a test of this ansatz using a sample of 17 relaxed galaxy groups observed using Chandra and XMM-Newton, as an extension of our previous analysis with galaxy clusters. We find ρc ∝ rc^(−1.35+/-0.16) with an intrinsic scatter of about 27.3%, which is about 1.5 times larger than that seen for galaxy clusters. Our results thereby indicate that the surface density is discrepant with respect to scale invariance by about 2σ, and its value is about four times greater than that for galaxies. Therefore, the elevated values of the halo surface density for groups and clusters indicate that the surface density cannot be a universal constant for all dark matter-dominated systems. Furthermore, we also implemented a test of the radial acceleration relation for this group sample. We find that the residual scatters in the radial acceleration relation are about 0.32 dex and a factor of three larger than that obtained using galaxy clusters. The acceleration scale which we obtain is in-between that seen for galaxies and clusters. |
