Gone after one orbit: How cluster environments quench galaxies

TL;DR

This study uses cosmological simulations to show that most satellite galaxies in clusters stop forming stars within 1 Gyr of infall, primarily due to ram-pressure stripping, with orbit type influencing star formation duration.

Contribution

It provides detailed orbital analysis of satellite galaxies, confirming ram-pressure stripping as the main quenching mechanism in clusters and highlighting orbit-dependent star formation cessation.

Findings

Star-forming satellites have radially dominated orbits.

Most satellites quench within 1 Gyr after infall.

Tangential orbits and high mass extend star formation duration.

Abstract

The effect of galactic orbits on a galaxy's internal evolution within a galaxy cluster environment has been the focus of heated debate in recent years. To understand this connection, we use both the $(0.5 \,$Gpc)$^3$ and the Gpc$^3$ boxes from the cosmological hydrodynamical simulation set Magneticum Pathfinder. We investigate the velocity-anisotropy, phase space, and the orbital evolution of up to $\sim 5 \cdot 10^{5}$ resolved satellite galaxies within our sample of 6776 clusters with $M_{\mathrm{vir}} > 10^{14} \, \mathrm{M_{\odot}}$ at low redshift, which we also trace back in time. In agreement with observations, we find that star-forming satellite galaxies inside galaxy clusters are characterised by more radially dominated orbits, independent of cluster mass. Furthermore, the vast majority of star-forming satellite galaxies stop forming stars during their first passage. We find a strong dichotomy both in line-of-sight and radial phase space between star-forming and quiescent galaxies, in line with observations. The tracking of individual orbits shows that the star-formation of almost all satellite galaxies drops to zero within $1 \, \mathrm{Gyr}$ after in-fall. Satellite galaxies that are able to remain star-forming longer are characterised by tangential orbits and high stellar mass. All this indicates that in galaxy clusters the dominant quenching mechanism is ram-pressure stripping.