Differences in the physical properties of satellite galaxies within relaxed and disturbed galaxy groups and clusters

¹ INAF – Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, 34143 Trieste, Italy
² Departamento de Astronomía, Universidad de La Serena, Avenida Juan Cisternas 1200, La Serena, Chile
³ Instituto de Investigación Multidisciplinar en Ciencia y Tecnología, Universidad de La Serena, Raúl Bitrán 1305, La Serena, Chile
⁴ Facultad de Ingeniería y Arquitectura, Universidad Central de Chile, Av. Francisco de Aguirre 0405, La Serena, Chile
⁵ Cerro Tololo Inter-American Observatory/NSF NOIRLab, Casilla 603, La Serena, Chile
⁶ International Gemini Observatory/NSF NOIRLab, Casilla 603, La Serena, Chile

^⋆ Corresponding author: franklin.aldas@inaf.it

Received: 5 August 2024
Accepted: 27 May 2025

Abstract

Aims. Galaxy groups and clusters are the most massive collapsed structures in the Universe. They assemble hierarchically through the successive mergers of smaller systems. These dense environments play a crucial role in driving the evolution and morphological transformation of their galaxies.

Methods. The dynamical state of groups and clusters can affect the properties of their galaxy populations. Our aim is to characterise the distribution of galaxies’ colour, specific star formation rate, quenched galaxy fraction, and gas availability in galaxies bounded to groups and clusters and to examine how these properties relate to the dynamical state of their host environments.

Results. We used the most massive halos (M>10¹³ M_⊙) in the Illustris TNG100 simulation and separated the sample into two categories: relaxed and disturbed halos. This classification was done based on the offset between the position of the brightest cluster galaxy (BCG) and the centre-of-mass of the gas. Subsequently, we classified their galaxy populations into red and blue galaxies using a threshold derived from a double Gaussian fit to their colour distribution. Additionally, we distinguished between star-forming and quenched galaxies by applying a threshold defined as one dex below the interpolated star formation main sequence.

Conclusions. Our findings reveal differences in physical properties such as colour, star formation rates, and gas availability among satellite galaxies bound to interacting clusters compared to relaxed clusters. Disturbed clusters exhibit more blue, star-forming galaxies than their relaxed counterparts. This discrepancy in the fraction of blue and star-forming galaxies can be attributed to higher gas availability, including hot, diffuse, and condensed gas in satellite galaxies in disturbed clusters compared to relaxed ones. Furthermore, our study shows that during cluster mergers, there are two crucial phases; at the beginning of interaction, there is an important boost in the star formation rate, followed by a suppression as the cluster reaches the equilibrium state.