The impact of ram pressure on cluster galaxies, insights from GAEA and TNG

¹ Tianjin Normal University, Binshuixidao 393, Tianjin, China
² INAF – Astronomical Observatory of Trieste, Via G.B. Tiepolo 11, I-34143 Trieste, Italy
³ IFPU – Institute for Fundamental Physics of the Universe, Via Beirut 2, 34151 Trieste, Italy
⁴ Dipartimento di Fisica G. Occhialini, Università degli Studi di Milano Bicocca, Piazza della Scienza 3, 20126 Milano, Italy
⁵ INAF – Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milano, Italy
⁶ Institute for Physics, Laboratory for Galaxy Evolution and Spectral Modelling, Ecole Polytechnique Federale de Lausanne, Observatoire de Sauverny, Chemin Pegasi 51, CH-1290 Versoix, Switzerland

^⋆ Corresponding author: xielizhi.1988@gmail.com

Received: 27 January 2025
Accepted: 17 April 2025

Abstract

Ram pressure stripping (RPS) has a non-negligible impact on the gas content of cluster galaxies. We used the semi-analytic model GAEA and the hydro-simulation TNG to investigate whether cluster galaxies suffer from strong RPS that is sufficient to remove a significant fraction of their gas during the first pericentric passage. We estimated that a ram pressure of 10^−10.5, 10⁻¹², 10^−13.5g cm⁻¹ s⁻² can remove 90%, 50%, and 20% of the cold gas reservoir from low-mass galaxies with 9 <  log M_⋆/M_⊙ < 9.5, assuming the gas can be stripped instantaneously. We then used this information to divide the phase space diagram into “strong”, “moderate”, “weak”, and “no” RPS zones. By tracing the orbit of galaxies since 2.5R_vir, we find in both GAEA and TNG that about half of the galaxies in Virgo-like halos ( log M_h/M_⊙ ∼ 14) did not suffer strong RPS during the first pericentric passage. In Coma-like halos ( log M_h/M_⊙ ∼ 15), almost all galaxies have suffered strong RPS during the first pericentric passage, which can remove all gas from low-mass galaxies but is insufficient to significantly reduce the gas content of more massive galaxies. In general, results from TNG and GAEA are consistent, with the RPS being only slightly stronger in TNG than in GAEA. Our findings suggest that most cluster galaxies maintain a notable fraction of their gas and continue forming stars after the first pericentric passage, except for those with a low stellar mass ( log M_⋆/M_⊙ < 9.5) in very massive halos ( log M_h/M_⊙ > 15).