Work

Characterising the formation and evolution of S0-galaxies (CaFES-0): Their formation pathways around galaxy clusters

Year: 2026

Type: article

Abstract: Context. The formation pathways of lenticular galaxies (S0s), which morphologically lie between elliptical and spiral galaxies, remain a topic of active research. Environmental effects, merging histories, and pre-processing mechanisms are often proposed as key factors influencing their transformation. However, the relative importance of these processes remains unclear, particularly when compared with other galaxy types. Aims. We investigated and quantified the role of the environment on the formation of S0s. Methods. We used the Hydrangea cosmological zoom-in simulation suite to analyse the environmental histories of S0 galaxies, defined here as quenched disk galaxies, both centrals and satellites. Results. We find that the vast majority (> 85%) of our sample of S0s are satellites in massive haloes (log 10 M 200 /M ⊙ > 13), while only ∼10% are centrals in low-mass haloes. Satellite S0s exhibit a highly quiescent merging history, with ∼75% experiencing no significant mergers since z = 2. Centrals show more varied merging histories, although our results may be affected by limited sample size. Contrary to expectations, no clear trends in merger ratios with morphology are observed. However, mergers involving lenticular and spiral galaxies tend to occur in low-density environments and are likely gas-rich, enabling disk reformation. Pre-processing effects in groups are critical, influencing both quenching and morphological transformation. Conclusions. Our results strongly suggest that S0 galaxies predominantly form from faded spirals in clusters, with a minority forming via mergers in smaller haloes. These results are in agreement with previous observations of lenticular galaxies around galaxy clusters.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202661485