The radial orbits of ram-pressure-stripped galaxies in clusters from the GASP survey

TL;DR

This study investigates the velocity anisotropy profiles of ram-pressure-stripped galaxies in clusters, revealing increasingly radial orbits from the center to the virial radius, using a large sample and multiple analysis methods.

Contribution

It provides the first detailed characterization of the orbital anisotropy of ram-pressure-stripped galaxies across cluster radii using combined dynamical modeling techniques.

Findings

Orbits become more radial with increasing distance from cluster center.

Ram-pressure-stripped galaxies have similar but more elongated orbits compared to spiral galaxies.

Orbits are nearly isotropic at the center and highly radial at the virial radius.

Abstract

We analyse a sample of 244 ram-pressure-stripped candidate galaxy members within the virial radius of 62 nearby clusters, to determine their velocity anisotropy profile $\beta(r)$. We use previously determined mass profiles for the 62 clusters to build an ensemble cluster by stacking the 62 cluster samples in projected phase-space. We solve the Jeans equation for dynamical equilibrium by two methods, MAMPOSSt and the Jeans inversion technique, and determine $\beta(r)$ both in parametric form and non-parametrically. The two methods consistently indicate that the orbits of the ram-pressure-stripped candidates are increasingly radial with distance from the cluster center, from almost isotropic ($\beta \simeq 0$) at the center, to very radial at the virial radius ($\beta \simeq 0.7$). The orbits of cluster galaxies undergoing ram-pressure stripping are similar to those of spiral cluster galaxies, but more radially elongated at large radii.