2020/09/29 by Kopenhafer, Claire, Starkenburg, Tjitske K., Tonnesen, Stephanie +1
#Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences
paper · doi:10.48550/arxiv.2009.14222
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 (Tuttle & Tonnesen 2020). In this paper, we search for breakBRD analogues 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 analogue 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\odot < 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.