Speaker
Description
The concentration–mass (c–M) relation of dark matter halos is a key prediction of hierarchical structure formation and provides an important link between cosmological simulations and observations of dark matter halos. While the standard trend predicts a monotonic decrease of concentration with increasing halo mass, several studies have suggested a possible deviation from this behavior at the high-mass end.
We present an analysis of the c–M relation of massive dark matter halos based on the latest update to the Uchuu cosmological simulation (Mucho Uchuu; Ishiyama et al., in prep). Our study focuses on halos in the mass range 13 < log M < 15.5, corresponding to group- and cluster-scale systems. In particular, we investigate how the inferred c–M relation depends on halo dynamical state by explicitly separating relaxed and unrelaxed halo populations.
We find that the behavior of the c–M relation differs significantly between these populations. The feature that appears at the massive end in the full halo sample is strongly suppressed when the analysis is restricted to relaxed halos, while it remains prominent for unrelaxed systems. This result indicates that the inferred concentration of massive halos is sensitive to ongoing mass accretion and non-equilibrium structure, rather than being determined solely by the equilibrium inner halo profile.
These findings suggest that the high-mass behavior of the c–M relation should be interpreted with caution, particularly in the presence of dynamically young or actively accreting halos. We discuss the implications of this result for theoretical modeling of halo structure, as well as for comparisons between simulations and observationally inferred halo properties.
| Other topic / keywords: | concentration–mass (c–M) relation of dark matter halos |
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