Constraining cluster masses from the stacked phase space distribution at large radii

Abstract

Velocity dispersions have been employed as a method to measure masses of clusters. To complement this conventional method, we explore the possibility of constraining cluster masses from the stacked phase space distribution of galaxies at larger radii, where infall velocities are expected to have a sensitivity to cluster masses. First, we construct a two component model of the three-dimensional phase space distribution of haloes surrounding clusters up to 50 h −1 Mpc from cluster centres based on N-body simulations. We find that the three-dimensional phase space distribution shows a clear cluster mass dependence up to the largest scale examined. We then calculate the probability distribution function of pairwise line-of-sight velocities between clusters and haloes by projecting the three-dimensional phase space distribution along the line-of-sight with the effect of the Hubble flow. We find that this projected phase space distribution, which can directly be compared with observations, shows a complex mass dependence due to the interplay between infall velocities and the Hubble flow. Using this model, we estimate the accuracy of dynamical mass measurements from the projected phase space distribution at the transverse distance from cluster centres larger than 2h −1 Mpc. We estimate that, by using 1.5 × 10 5 spectroscopic galaxies, we can constrain the mean cluster masses with an accuracy of 14.5% if we fully take account of the systematic error coming from the inaccuracy of our model. This can be improved down to 5.7% by improving the accuracy of the model.

the threehundred: the structure and properties of cosmic filaments in the outskirts of galaxy clusters

“…Both show a similar behaviour: a collective movement of particles falling towards the filament at ≈250h −1 km s −1 (indicated by negative velocities) from larger distances, and large random motions inside the filament (as indicated by the vertical dashed lines). This plot is quite similar to the ones done stacking haloes (Oman, Hudson & Behroozi 2013;Arthur et al 2019;Hamabata, Oguri & Nishimichi 2019), but in this case we integrate along the filament axis and stack afterwards. In this way, we see how this structures that as a whole are not yet virialized, when we integrate their properties in a symmetric direction, we recover virial properties.…”

The Phase Space Structure of Dark Matter Halos

“…Motivated by analysis in the companion paper by Tomooka et al, in this work we set out to determine whether a detailed study of the phase space structure of dark matter halos can shed light on what the true extent of a halo is. The phase space structure of a dark matter halo can be used to constrain cosmology through cluster mass measurements (Evrard et al 2008;Munari et al 2013;Bocquet et al 2015;Hamabata et al 2019), to constrain modified gravity models (Schmidt 2010;Lam et al 2012;Zu et al 2014;Mitchell et al 2018) and to understand astrophysical processes such as assembly bias (Hearin 2015;Xu & Zheng 2018). The velocity structure inside the halo is virialized, with an average radial velocity of 0 and a dispersion directly related to the mass of the halo (Evrard et al 2008).…”

Clusters Have Edges: The Projected Phase SpaceStructure of SDSS redMaPPer Clusters

“…Our work is most closely related to the pioneering work by Zu & Weinberg (2013), and the more recent update to that work by Hamabata et al (2019). Both of these works are based on numerical simulations.…”

“…Many of the qualitative conclusions of our work are already apparent in these works, though the emphasis and conclusions drawn are different. In particular, both Zu & Weinberg (2013) and Hamabata et al (2019) were primarily interested in characterizing the infalling region of the galaxy clusters, and the extent to which these infall regions can be used for cluster mass calibration and studies of modified gravity (e.g. Zu et al 2014).…”