TY - JOUR
T1 - A relationship between stellar metallicity gradients and galaxy age in dwarf galaxies
AU - Mercado, Francisco J.
AU - Bullock, James S.
AU - Boylan-Kolchin, Michael
AU - Moreno, Jorge
AU - Wetzel, Andrew
AU - El-Badry, Kareem
AU - Graus, Andrew S.
AU - Fitts, Alex
AU - Hopkins, Philip F.
AU - Faucher-Giguère, Claude André
AU - Gurvich, Alexander B.
N1 - Publisher Copyright:
© 2021 2020 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
PY - 2021/3/1
Y1 - 2021/3/1
N2 - We explore the origin of stellar metallicity gradients in simulated and observed dwarf galaxies. We use FIRE-2 cosmological baryonic zoom-in simulations of 26 isolated galaxies as well as existing observational data for 10 Local Group dwarf galaxies. Our simulated galaxies have stellar masses between 105.5 and 108.6 MO. Whilst gas-phase metallicty gradients are generally weak in our simulated galaxies, we find that stellar metallicity gradients are common, with central regions tending to be more metal-rich than the outer parts. The strength of the gradient is correlated with galaxy-wide median stellar age, such that galaxies with younger stellar populations have flatter gradients. Stellar metallicty gradients are set by two competing processes: (1) the steady 'puffing' of old, metal-poor stars by feedback-driven potential fluctuations and (2) the accretion of extended, metal-rich gas at late times, which fuels late-time metal-rich star formation. If recent star formation dominates, then extended, metal-rich star formation washes out pre-existing gradients from the 'puffing' process. We use published results from ten Local Group dwarf galaxies to show that a similar relationship between age and stellar metallicity-gradient strength exists among real dwarfs. This suggests that observed stellar metallicity gradients may be driven largely by the baryon/feedback cycle rather than by external environmental effects.
AB - We explore the origin of stellar metallicity gradients in simulated and observed dwarf galaxies. We use FIRE-2 cosmological baryonic zoom-in simulations of 26 isolated galaxies as well as existing observational data for 10 Local Group dwarf galaxies. Our simulated galaxies have stellar masses between 105.5 and 108.6 MO. Whilst gas-phase metallicty gradients are generally weak in our simulated galaxies, we find that stellar metallicity gradients are common, with central regions tending to be more metal-rich than the outer parts. The strength of the gradient is correlated with galaxy-wide median stellar age, such that galaxies with younger stellar populations have flatter gradients. Stellar metallicty gradients are set by two competing processes: (1) the steady 'puffing' of old, metal-poor stars by feedback-driven potential fluctuations and (2) the accretion of extended, metal-rich gas at late times, which fuels late-time metal-rich star formation. If recent star formation dominates, then extended, metal-rich star formation washes out pre-existing gradients from the 'puffing' process. We use published results from ten Local Group dwarf galaxies to show that a similar relationship between age and stellar metallicity-gradient strength exists among real dwarfs. This suggests that observed stellar metallicity gradients may be driven largely by the baryon/feedback cycle rather than by external environmental effects.
KW - cosmology: theory
KW - galaxies: dwarf
KW - galaxies: formation
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U2 - 10.1093/mnras/staa3958
DO - 10.1093/mnras/staa3958
M3 - Article
AN - SCOPUS:85100766346
VL - 501
SP - 5121
EP - 5134
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 4
ER -