Quenching Timescales in the IllustrisTNG Simulation

Dan Walters; Joanna Woo; Sara L. Ellison

doi:10.1093/mnras/stac283

paper

Quenching Timescales in the IllustrisTNG Simulation

arXiv:2202.00015 · doi:10.1093/mnras/stac283

Abstract

The timescales for galaxy quenching offer clues to its underlying physical drivers. We investigate central galaxy quenching timescales in the IllustrisTNG 100-1 simulation, their evolution over time, and the pre-quenching properties of galaxies that predict their quenching timescales. Defining quenching duration $τ_{q}$ as the time between crossing sSFR thresholds, we find that $\sim$ 40% of galaxies quench rapidly with $τ_{q} <$ 1 Gyr, but a substantial tail of galaxies can take up to 10 Gyr to quench. Furthermore, 29% of galaxies that left the star forming main sequence (SFMS) more than 2 Gyr ago never fully quench by $z = 0$ . While the median $τ_{q}$ is fairly constant with epoch, the rate of galaxies leaving the SFMS increases steadily over cosmic time, with the rate of slow quenchers being dominant around $z \sim 2$ to 0.7. Compared to fast quenchers ( $τ_{q} <$ 1 Gyr), slow-quenching galaxies ( $τ_{q} >$ 1 Gyr) were more massive, had more massive black holes, had larger stellar radii and accreted gas with higher specific angular momentum (AM) prior to quenching. These properties evolve little by $z = 0$ , except for the accreting gas AM for fast quenchers, which reaches the same high AM as the gas in slow quenchers. By $z = 0$ , slow quenchers also have residual star formation in extended gas rings. Using the expected relationship between stellar age gradient and $τ_{q}$ for inside-out quenching we find agreement with MaNGA IFU observations. Our results suggest the accreting gas AM and potential well depth determine the quenching timescale.

18 pages, 18 figures, accepted for publication in MNRAS

Quenching Timescales in the IllustrisTNG Simulation

Abstract

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