THE THREE HUNDRED: cluster dynamical states and relaxation period
Abstract
We introduce a new parameter λDS to quantify the dynamical state of galaxy clusters and test it using simulations from THE THREE HUNDRED cluster zoom suite. λDS is a combination of three previously used dynamical state measures, namely virial ratio, centre of mass offset, and substructure mass fraction, crafted to assume a double-Gaussian distribution, thereby yielding a natural division between relaxed and unrelaxed clusters where the Gaussians cross. Using dark matter-only simulations, we identify the optimal separator to be λDS = 3.424. We test this same criterion on two sets of fully hydrodynamical THE THREE HUNDRED runs (GADGET-X and GIZMO-SIMBA), and find only a weak dependence on the input baryonic physics. We correlate the evolution of λDS with the mass accretion history and find that halo mass changes of $\frac{\Delta M_{200}}{M_{200}} \lesssim 0.12$ do not typically alter the dynamical state. We examine the relaxation period, defined as the time taken to return to relaxation after becoming disturbed, and find a correlation between this relaxation period and the strength of halo mass change $\frac{\Delta M_{200}}{M_{200}}$. By fitting this correlation, we show that the relaxation period can be estimated from $\frac{\Delta M_{200}}{M_{200}}$ (even for multiple mass accretion events) with good accuracy.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2022
- DOI:
- 10.1093/mnras/stac2171
- arXiv:
- arXiv:2112.01909
- Bibcode:
- 2022MNRAS.516...26Z
- Keywords:
-
- galaxies: clusters: general;
- galaxies: evolution;
- galaxies: haloes;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 13 pages, 12 figures, comments are welcome