The breakBRD Breakdown: Using IllustrisTNG to Track the Quenching of an Observationally Motivated Sample of Centrally Star-forming Galaxies

The observed breakBRD ("break bulges in red disks") galaxies are a nearby sample of face-on disk galaxies with particularly centrally concentrated star formation: they have red disks but recent star formation in their centers as measured by the Dn4000 spectral index. In this paper, we sear...

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Bibliographic Details
Published in:The Astrophysical journal 2020-11, Vol.903 (2), p.143
Main Authors: Kopenhafer, Claire, Starkenburg, Tjitske K., Tonnesen, Stephanie, Tuttle, Sarah
Format: Article
Language:English
Subjects:
Analogs
Astronomical simulations
Astronomy & Astrophysics
Astrophysics
Disk galaxies
Galactic bulge
Galaxy environments
Galaxy evolution
Galaxy physics
Galaxy processes
Galaxy quenching
Quenching
Space telescopes
Star & galaxy formation
Star formation
Stars & galaxies
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Summary:The observed breakBRD ("break bulges in red disks") galaxies are a nearby sample of face-on disk galaxies with particularly centrally concentrated star formation: they have red disks but recent star formation in their centers as measured by the Dn4000 spectral index. In this paper, we search for breakBRD analogs in the IllustrisTNG simulation and describe their history and future. We find that a small fraction (∼4% at z = 0; ∼1% at z = 0.5) of galaxies fulfill the breakBRD criteria, in agreement with observations. In comparison with the mass-weighted parent IllustrisTNG sample, these galaxies tend to consist of a higher fraction of satellite and splashback galaxies. However, the central, non-splashback breakBRD galaxies show similar environments, black hole masses, and merger rates, indicating that there is not a single formation trigger for inner star formation and outer quenching. We determine that breakBRD analog galaxies as a whole are in the process of quenching. The breakBRD state, with its highly centrally concentrated star formation, is uncommon in the history of either currently quiescent or star-forming galaxies; however, approximately 10% of 1010 < M*/M < 1011 quiescent galaxies at z = 0 have experienced SFR concentrations comparable to those of the breakBRDs in their past. Additionally, the breakBRD state is short lived, lasting a few hundred Myr up to ∼2 Gyr. The observed breakBRD galaxies may therefore be a unique sample of outside-in quenching galaxies.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.3847/1538-4357/abbd9c