The mass function dependence on the dynamical state of dark matter haloes
Abstract
Context. Galaxy clusters are luminous tracers of the most massive dark matter haloes in the Universe. To use them as a cosmological probe, a detailed description of the properties of dark matter haloes is required.
Aims: We characterize how the dynamical state of haloes impacts the dark matter halo mass function at the highmass end (i.e., for haloes hosting clusters of galaxies).
Methods: We used the dark matteronly MultiDark suite of simulations and the highmass objects M > 2.7 × 10^{13} M_{⊙} h^{−1} therein. We measured the mean relations of concentration, offset, and spin as a function of dark matter halo mass and redshift. We investigated the distributions around the mean relations. We measured the dark matter halo mass function as a function of offset, spin, and redshift. We formulated a generalized mass function framework that accounts for the dynamical state of the dark matter haloes.
Results: We confirm the recent discovery of the concentration upturn at high masses and provide a model that predicts the concentration for different values of mass and redshift with one single equation. We model the distributions around the mean values of concentration, offset, and spin with modified Schechter functions. We find that the concentration of lowmass haloes shows a faster redshift evolution compared to highmass haloes, especially in the highconcentration regime. We find that the offset parameter is systematically smaller at low redshift, in agreement with the relaxation of structures at recent times. The peak of its distribution shifts by a factor of ∼1.5 from z = 1.4 to z = 0. The individual models are combined into a comprehensive mass function model, which predicts the mass function as a function of spin and offset. Our model recovers the fiducial mass function with ∼3% accuracy at redshift 0 and accounts for redshift evolution up to z ∼ 1.5.
Results: This new approach accounts for the dynamical state of the halo when measuring the halo mass function. It offers a connection with dynamical selection effects in galaxy cluster observations. This is key toward precision cosmology using cluster counts as a probe.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 August 2021
 DOI:
 10.1051/00046361/202039123
 arXiv:
 arXiv:2008.03179
 Bibcode:
 2021A&A...652A.155S
 Keywords:

 cosmology: theory;
 galaxies: clusters: general;
 Xrays: galaxies: clusters;
 dark matter;
 cosmology: observations;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 to be published in Astronomy&