Are early-type galaxies quenched by present-day environment? A study of dwarfs in the Fornax Cluster

Abstract: Galaxies undergo processes throughout their lifetimes that ultimately lead to the expulsion of the gas and the cessation of the star-forming activity. This phenomenon commonly known as quenching, can be caused by environmental processes. For this we use the results of Romero-G\'omez et al. (2024), who analyzed galaxies from the SAMI-Fornax and ATLAS$^{3D}$ survey. Using t${90}$ as an approximation for the quenching time and comparing it with the infall time derived from phase-space models, we determine the probability of the quenching being produced by the local environment of galaxies. Our results reveal a relation between galaxy mass and quenching probability. Down to M${\star}$ $\sim$10$^{10}$ M${\odot}$, galaxies exhibit almost zero probability of quenching, suggesting their independence from environmental effects. As we move into the mass regime of dwarf galaxies, the probability increases with decreasing mass, highlighting their sensitivity to environmental quenching. For the dwarfs, 10$^{7}$ - 10$^{9}$ M${\odot}$, 36$\pm$9% of our observational data are consistent with this hypothesis, challenging the idea that the present-day cluster, Fornax, is the primary driver of quenching in the low mass galaxies. We compare these results with cosmological simulations, selecting galaxies under similar conditions to our observational sample. The simulated sample shows lower quenching probabilities as we move down in mass, only 5$\pm$1% of galaxies meet the quenching criteria. This discrepancy between observations and simulations underlines that modelling quenching is still in its infancy. In general, the number of observed galaxies quenched by their environment is lower than expected, which suggests that pre-processing plays a larger role in galaxy evolution. Ultimately, our results highlight the need for higher-quality simulations and refinement of galaxy formation and evolution models.