Fast and slow paths to quiescence : ages and sizes of 400 quiescent galaxies from the LEGA-C survey

Wu, Po-Feng and Wel, Arjen van der and Bezanson, Rachel and Gallazzi, Anna and Pacifici, Camilla and Straatman, Caroline M. S. and Barisic, Ivana and Bell, Eric F. and Chauke, Priscilla and Houdt, Josha van and Franx, Marijn and Muzzin, Adam and Sobral, David and Wild, Vivienne (2018) Fast and slow paths to quiescence : ages and sizes of 400 quiescent galaxies from the LEGA-C survey. The Astrophysical Journal, 868 (1): 37. ISSN 0004-637X

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We analyze the stellar age indicators (Dn4000 and EW(Hδ)) and sizes of 467 quiescent galaxies with M ∗ ≥ 1010 M o at z ∼ 0.7 drawn from DR2 of the LEGA-C survey. Interpreting index variations in terms of equivalent single stellar population age, we find that the median stellar population is younger for larger galaxies at fixed stellar mass. The effect is significant, yet small; the ages of the larger and smaller subsets differ by only <500 Myr, much less than the age variation among individual galaxies (∼1.5 Gyr). At the same time, post-starburst galaxies - those that experienced recent and rapid quenching events - are much smaller than expected based on the global correlation between age and size of normal quiescent galaxies. These coexisting trends unify seemingly contradictory results in the literature; the complex correlations between size and age indicators revealed by our large sample of galaxies with high-quality spectra suggest that there are multiple evolutionary pathways to quiescence. Regardless of the specific physical mechanisms responsible for the cessation of star formation in massive galaxies, the large scatter in Dn4000 and EW(Hδ) immediately implies that galaxies follow a large variety of evolutionary pathways. On the one hand, we see evidence for a process that slowly shuts off star formation and transforms star-forming galaxies to quiescent galaxies without necessarily changing their structures. On the other hand, there is likely a mechanism that rapidly quenches galaxies, an event that coincides with dramatic structural changes, producing post-starburst galaxies that can be smaller than their progenitors. © 2018. The American Astronomical Society. All rights reserved.

Item Type:
Journal Article
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The Astrophysical Journal
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This is an author-created, un-copyedited version of an article accepted for publication/published in The Astrophysical Journal. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at doi: 10.3847/1538-4357/aae822
Uncontrolled Keywords:
?? galaxies: evolutiongalaxies: formationgalaxies: high-redshiftgalaxies: stellar contentgalaxies: structureastronomy and astrophysicsspace and planetary science ??
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11 Oct 2018 13:02
Last Modified:
15 Jul 2024 18:21