Speaker
Description
Galaxy clusters are powerful cosmological probes and play a central role in constraining the properties of dark matter through their mass function and abundance evolution. However, cluster mass estimates derived from intra-cluster medium observations typically assume hydrostatic equilibrium, introducing a systematic bias that propagates into cosmological and dark matter constraints. This bias is expected to be particularly significant during strong assembly phases, such as major mergers, potentially affecting precision measurements relevant to dark matter studies.
In this work, we investigate how cluster mergers impact the evolution of the hydrostatic mass bias across cosmic time and assess the physical mechanisms driving its variability. We analyse a sample of cluster mergers identified in cosmological simulations spanning the redshift range
1.5>z>0. True masses are compared with hydrostatic estimates computed within the virial volume from gas density and temperature profiles, and their evolution is connected to merger histories derived from halo merger trees.
We find that the bias exhibits a characteristic time-dependent pattern during major mergers: a pronounced negative dip around the merger time, followed by a transient positive peak and a gradual relaxation to pre-merger levels. This evolution is primarily driven by morphological reconfigurations of the intra-cluster gas density rather than thermodynamic effects. The trend shows little dependence on secondary merger parameters and can be described by a simple time-dependent functional form. Similar behaviour is observed at smaller radii, with reduced amplitude and shorter timescales.
Our results demonstrate that the hydrostatic mass bias is tightly linked to cluster assembly history, with direct implications for cluster-based cosmological analyses. Accurately modelling this time-dependent bias is essential to reduce systematic uncertainties in cluster mass calibration and to improve the robustness of dark matter constraints derived from cluster surveys.
| Main Contribution topic | Cosmology Dark Matter |
|---|---|
| Secondary contribution topic | Indirect detection |