Baker, Maximilian K., Davis, Timothy A.  ORCID: https://orcid.org/0000-0003-4932-9379, van de Voort, Freeke ORCID: https://orcid.org/0000-0002-6301-638X and Ruffa, Ilaria
2025.
Stellar-gas kinematic misalignments in eagle: lifetimes and longevity of misaligned galaxies.
Monthly Notices of the Royal Astronomical Society
541
(1)
, pp. 494-515.
10.1093/mnras/staf977
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Abstract
The dominant processes by which galaxies replenish their cold gas reservoirs remain disputed, especially in massive galaxies. Stellar-gas kinematic misalignments offer an opportunity to study these replenishment processes. However, observed distributions of these misalignments conflict with current models of gas replenishment in early-type galaxies (ETGs), with longer relaxation timescales suggested as a possible solution. We use the eagle simulation to explore the relaxation of unstable misaligned gas in galaxies with masses of M* ≥ 109.5 M⊙ between 0 < z < 1. We extract misalignments from formation to relaxation providing a sample of ∼3200 relaxations. We find relaxation timescales tend to be short-duration, with median lifetimes of ∼0.5 Gyr, though with a notable population of unstable misalignments lasting ≳ 1 Gyr. Relaxation time distributions show a log-linear relationship, with of unstable misalignments persisting for ≳ 3 torquing times. Long-lived unstable misalignments are predominantly found in galaxies with higher stellar masses, lower star-forming gas fractions, higher ongoing gas inflow, and which reside in the centres of dense environments. Mergers only cause of unstable misalignments among galaxies at z < 0.35, and ≈21% at 0.35 < z < 1.0 in eagle. We conclude that, at least in eagle, unstable kinematic misalignments are not predominantly driven by gas-rich minor mergers at any redshift probed. Additionally, processes that significantly extend relaxation times are not dominant in the galaxy population. Instead, we see a diverse formation pathway for misalignments such as through hot halo cooling.
| Item Type: | Article |
|---|---|
| Date Type: | Publication |
| Status: | Published |
| Schools: | Schools > Physics and Astronomy |
| Publisher: | Oxford University Press |
| ISSN: | 0035-8711 |
| Date of First Compliant Deposit: | 12 June 2025 |
| Date of Acceptance: | 8 June 2025 |
| Last Modified: | 06 Aug 2025 12:46 |
| URI: | https://orca.cardiff.ac.uk/id/eprint/179034 |
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