Diving into dangerous tides: The impact of galaxy cluster tidal environments on satellite galaxy mass densities

TL;DR

This paper investigates how tidal forces in galaxy clusters influence satellite galaxy densities, revealing a distance-dependent segregation in mass density profiles and proposing a new diagnostic tool for gravitational field strength.

Contribution

It combines semi-analytical models with cosmological simulations to demonstrate the impact of tidal environments on satellite density profiles and introduces the transition radius as a diagnostic for tidal processing.

Findings

Satellite densities decrease with proximity to cluster centers.

A characteristic transition radius marks the change in density profiles.

Observational data supports the predicted density segregation.

Abstract

Satellite galaxies endure powerful environmental tidal forces that drive mass stripping of their outer regions. Consequently, satellites located in central regions of galaxy clusters or groups, where the tidal field is strongest, are expected to retain their central dense regions while losing their outskirts. This process produces a spatial segregation in the mean mass density with the cluster-centric distance (the $\bar{\rho}-r$ relation). To test this hypothesis, we combined semi-analytical satellite orbital models with cosmological galaxy simulations. We find that not only the mean total mass densities ($\bar{\rho}$), but also the mean stellar mass densities ($\bar{\rho}^{\star}$) of satellites exhibit this distance-dependent segregation ($\bar{\rho}^{\star}-r$). The correlation traces the host's tidal field out to a characteristic transition radius at $\Re_{\star}$ $\approx$ $0.5$ $R_{\rm vir}$, beyond which the satellite population's density profile can have a slight increase or remain flat, reflecting the weakened tidal influence in the outskirts of galaxy clusters and beyond. We compare these predictions with observational data from satellites in the Virgo and Fornax galaxy clusters, as well as the Andromeda and Milky Way systems. Consistent trends in the satellite mean stellar mass densities are observed across these environments. Furthermore, the transition radius serves as a photometric diagnostic tool: it identifies regions where the stellar components of satellites underwent significant tidal processing and probes the gravitational field strength of the host halo.