BREATHING FIRE: HOW STELLAR FEEDBACK DRIVES RADIAL MIGRATION, RAPID SIZE FLUCTUATIONS, AND POPULATION GRADIENTS IN LOW-MASS GALAXIES

ABSTRACT We examine the effects of stellar feedback and bursty star formation on low-mass galaxies (Mstar = 2 × 106 − 5 × 1010 M ) using the Feedback in Realistic Environments (FIRE) simulations. While previous studies emphasized the impact of feedback on dark matter profiles, we investigate the imp...

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Published in:The Astrophysical journal 2016-04, Vol.820 (2), p.131-131
Main Authors: El-Badry, Kareem, Wetzel, Andrew, Geha, Marla, Hopkins, Philip F., Kereš, Dusan, Chan, T. K., Faucher-Giguère, Claude-André
Format: Article
Language:English
Subjects:
AGE DEPENDENCE
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BARYONS
ENVIRONMENT
Feedback
Fluctuation
FLUCTUATIONS
GALAXIES
galaxies: dwarf
galaxies: evolution
galaxies: kinematics and dynamics
galaxies: star formation
MASS
Mathematical models
METALLICITY
Migration
NONLUMINOUS MATTER
ORBITS
Outflow
STAR EVOLUTION
Star formation
STARS
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Summary:ABSTRACT We examine the effects of stellar feedback and bursty star formation on low-mass galaxies (Mstar = 2 × 106 − 5 × 1010 M ) using the Feedback in Realistic Environments (FIRE) simulations. While previous studies emphasized the impact of feedback on dark matter profiles, we investigate the impact on the stellar component: kinematics, radial migration, size evolution, and population gradients. Feedback-driven outflows/inflows drive significant radial stellar migration over both short and long timescales via two processes: (1) outflowing/infalling gas can remain star-forming, producing young stars that migrate ∼1 kpc within their first 100 Myr, and (2) gas outflows/inflows drive strong fluctuations in the global potential, transferring energy to all stars. These processes produce several dramatic effects. First, galaxies' effective radii can fluctuate by factors of >2 over ∼200 Myr, and these rapid size fluctuations can account for much of the observed scatter in the radius at fixed Mstar. Second, the cumulative effects of many outflow/infall episodes steadily heat stellar orbits, causing old stars to migrate outward most strongly. This age-dependent radial migration mixes-and even inverts-intrinsic age and metallicity gradients. Thus, the galactic-archaeology approach of calculating radial star formation histories from stellar populations at z = 0 can be severely biased. These effects are strongest at Mstar 107-9.6 M , the same regime where feedback most efficiently cores galaxies. Thus, detailed measurements of stellar kinematics in low-mass galaxies can strongly constrain feedback models and test baryonic solutions to small-scale problems in ΛCDM.
ISSN:0004-637X
1538-4357
DOI:10.3847/0004-637X/820/2/131