The two formation pathways of S0 galaxies

Abstract

Despite their ubiquity throughout the Universe, the formation of S0 galaxies remains uncertain. Recent observations have revealed that S0 galaxies make up a diverse population which is difficult to explain with a single formation pathway, suggesting that the picture of how these galaxies form is more complicated than originally envisioned. Here we take advantage of the latest hydrodynamical cosmological simulations and follow up these studies with an investigation into the formation histories of S0s in IllustrisTNG. We first classify IllustrisTNG galaxies in a way which is fully consistent with the observations, and reproduce the observed photometric and environmental distributions seen for the S0 population. We then trace the formation histories of S0 galaxies back through time, identifying two main distinct pathways; those which experienced gas stripping via group infalls (37 percent of S0s) or significant merger events (57 percent). We find that those forming via mergers feature a transient star-forming ring, whose present-day occurrence rate matches observations. We find that these formation pathways together can reproduce the range in rotational support in observed S0s, concluding that there are two main formation pathways for S0 galaxies.

17 pages, 16 figures, accepted for publication in MNRAS

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Cited by in corpus (8)

• Morphological decomposition of TNG50 galaxies: methodology and catalogue
• Merger histories of brightest group galaxies from MUSE stellar kinematics
• MaNGA galaxy properties -- II. A detailed comparison of observed and simulated spiral galaxy scaling relations
• Lessons Learned from the Two Largest Galaxy Morphological Classification Catalogues built by Convolutional Neural Networks
• The local Universe in the era of large surveys -- II. Multi-wavelength characterisation of activity in nearby S0 galaxies
• The present-day globular cluster kinematics of lenticular galaxies from the E-MOSAICS simulations and their relation to the galaxy assembly histories
• Star-forming S0 Galaxies in SDSS-MaNGA: fading spirals or rejuvenated S0s?
• Using the EAGLE simulations to elucidate the origin of disc surface brightness profile breaks as a function of mass and environment