The Three Hundred project: shapes and radial alignment of satellite, infalling, and backsplash galaxies

Abstract

Using 324 numerically modelled galaxy clusters, we investigate the radial and galaxy–halo alignment of dark matter subhaloes and satellite galaxies orbiting within and around them. We find that radial alignment depends on distance to the centre of the galaxy cluster but appears independent of the dynamical state of the central host cluster. Furthermore, we cannot find a relation between radial alignment of the halo or galaxy shape with its own mass. We report that backsplash galaxies, i.e. objects that have already passed through the cluster radius but are now located in the outskirts, show a stronger radial alignment than infalling objects. We further find that there exists a population of well radially aligned objects passing very close to the central cluster’s centre that were found to be on highly radial orbit.

The Three Hundred Project: Substructure in hydrodynamical and dark matter simulations of galaxy groups around clusters

“…However, the large deficit of extremely high-velocity haloes (v 2vcir) in the dark matteronly simulations could indeed be a result of tidal effects. Similarly, the (small) deficit of backsplash galaxies around our dark matter-only clusters could also be due to tidal effects, as backsplash galaxies are known to follow highly radial orbits and so experience strong tidal forces (Knebe et al 2020).…”

“…We also remove all objects from the hydrodynamical simulations that contain more than 30% of their mass in stars. These haloes are typically found very close to the centre of a larger halo, meaning that much of their dark matter has been stripped (evidence of this tidal stripping in TheThreeHundred simulations is presented in Knebe et al (2020)). The remnants of this process are very compact objects with high stellar mass fractions, whose properties (such as their radii and masses) are not well-determined by our halo finder.…”

The Three Hundred project: quest of clusters of galaxies morphology and dynamical state through Zernike polynomials

“…The proposed approach of studying morphology of galaxy clusters with Zernike polynomials is applied on tSZ maps of synthetic clusters extracted from THE THREE HUNDRED project 3 (Cui et al 2018). The dataset is composed of 324 clusters selected initially among the most massive objects (virial mass 8×10 14 ℎ −1 𝑀 at 𝑧 = 0) in MultiDark simulation (Klypin et al 2016) The reliability of the catalogue has been validated studying galaxy properties (Wang et al 2018), the evolution of the gas density profile (Mostoghiu et al 2019), the ram pressure stripping on the gas content of haloes and subhaloes (Arthur et al 2019), the hydrostatic equilibrium mass bias (Ansarifard et al 2020), backsplash galaxies (Haggar et al 2020), the filaments in and around cluster environments (Kuchner et al 2020), alignment of galaxies with respect to the host haloes (Knebe et al 2020), profiles and distributions of the baryonic components of the clusters (Li et al 2020), and dynamical state of galaxy clusters from multi-wavelength data (DL20). Other applications are on-going.…”

The THREEHUNDRED project: The effect of baryon processes at galaxy cluster scale

“…Benefiting from the large volume of these re-simulated cluster regions, detailed relations between the central cluster and the filaments connecting to it have been studied [16][17][18]. Furthermore, the cluster backsplash galaxies [19,20] and shock radius [21] have also been well addressed. The advanced baryon models in hydrodynamic simulations allow us to perform a detailed investigation on the cluster properties, such as profiles [22,23], substructure and its baryonic content [24][25][26][27], dynamical state and morphology [28,29], cluster (non-)thermalization [30,31], the fundamental plane [32], and the cluster mass biases [33, for hydrostatic-equilibrium assumption], [34, for sigma-mass relation] and [35, for weaklensing].…”