The SAMI galaxy survey: A range in S0 properties indicating multiple formation pathways

Simon Deeley, Michael J. Drinkwater, Sarah M. Sweet, Jonathan Diaz, Kenji Bekki, Warrick J. Couch, Duncan A. Forbes, Joss Bland-Hawthorn, Julia J. Bryant, Scott Croom, Luca Cortese, Jon S. Lawrence, Nuria Lorente, Anne M. Medling, Matt Owers, Samuel N. Richards, Jesse Van De Sande

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)


It has been proposed that S0 galaxies are either fading spirals or the result of galaxy mergers. The relative contribution of each pathway and the environments in which they occur remain unknown. Here, we investigate stellar and gas kinematics of 219 S0s in the SAMI Survey to look for signs of multiple formation pathways occurring across the full range of environments. We identify a large range of rotational support in their stellar kinematics, which correspond to ranges in their physical structure. We find that pressure-supported S0s with v/σ below 0.5 tend to be more compact and feature misaligned stellar and gas components, suggesting an external origin for their gas. We postulate that these S0s are consistent with being formed through a merger process. Meanwhile, comparisons of ellipticity, stellar mass, and Sérsic index distributions with spiral galaxies show that the rotationally supported S0s with v/σ above 0.5 are more consistent with a faded spiral origin. In addition, a simulated merger pathway involving a compact elliptical and gas-rich satellite results in an S0 that lies within the pressure-supported group. We conclude that two S0 formation pathways are active, with mergers dominating in isolated galaxies and small groups, and the faded spiral pathway being most prominent in large groups (1013 < Mhalo < 1014).

Original languageEnglish
Pages (from-to)2372-2383
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - Oct 2020


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