BreakBRD Galaxies: Evolutionary Clues Through an Analysis of Gas Content
The Astrophysical Journal(2024)
Abstract
By combining newly obtained deep GBT 21cm observations with optical
spectroscopic data, we present an analysis of the gas content of BreakBRD
galaxies, a population denoted by their blue star-forming centers and red
quenched disks that do not appear to follow the typical inside-out evolution of
spiral galaxies. We confirm previous results that the neutral atomic hydrogen
(HI) gas fractions of BreakBRDs are on-average lower than those of typical
galaxies on the star-forming sequence (SFS), and find that their H1
fractions are generally higher than Green Valley (GV) galaxies. HI depletion
times for BreakBRDs are roughly an order of magnitude lower than those of SFS
galaxies, in stark contrast with GV galaxies that typically have much longer
depletion times than SFS galaxies. The nuclear gas-phase metallicities of
BreakBRDs have a broader distribution than SFS galaxies and are skewed towards
slightly above-average values. BreakBRDs are systematically offset from the
Baryonic Tully-Fisher Relation towards lower baryonic mass at a given rotation
velocity. They also have higher typical HI asymmetries than SFS galaxies, and
of those galaxies with spatially resolved gas velocity fields from the SDSS-IV
MaNGA survey, two-thirds are either highly distorted or completely misaligned
relative to the stellar disk. Evidence supports a scenario where BreakBRDs are
in an early phase of quenching, and there is mixed evidence that their behavior
is related to past merger activity.
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Key words
Galaxies,Galactic and extragalactic astronomy,Disk galaxies,Interstellar medium,Interstellar atomic gas,Star formation
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