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

¹ Vicerrectoría de Investigación y Postgrado, Universidad de La Serena, La Serena 1700000, Chile
² Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago 7820436, Chile
³ Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile
⁴ Centro de Astro-Ingeniería, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago 7820436, Chile
⁵ Las Campanas Observatory, Carnegie Observatories, Casilla 601, La Serena 7820436, Chile
⁶ Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, Valparaíso, Chile
⁷ Gemini Observatory, South Operations Center, Casilla 603, La Serena, Chile
⁸ Department of Physics and Astronomy Galileo Galilei, University of Padua, Via Marzolo, 8-35131 Padua, Italy

^⋆ Corresponding author: matias.blana.astronomy@gmail.com

Received: 6 February 2024
Accepted: 12 May 2025

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 ρ̄−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 (ρ̄), but also the mean stellar mass densities (ρ̄^⋆) of satellites exhibit this distance-dependent segregation (ρ̄^⋆−r). The correlation traces the host’s tidal field out to a characteristic transition radius at ℜ_⋆​ ≈ ​0.5 R_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.