Kavli Affiliate: Mark Vogelsberger
| First 5 Authors: Alex M. Garcia, Alex M. Garcia, , ,
| Summary:
The metallicity of galaxies, and its variation with galactocentric radius,
provides key insights into the formation histories of galaxies and the physical
processes driving their evolution. In this work, we analyze the radial
metallicity gradients of star forming galaxies in the EAGLE, Illustris,
IllustrisTNG, and SIMBA cosmological simulations across a broad mass
($10^8.0M_odotleq M_star lesssim10^12.0M_odot$) and redshift ($0leq
zleq8$) range. We find that all simulations predict strong negative (i.e.,
radially decreasing) metallicity gradients at early cosmic times, likely due to
their similar treatments of relatively smooth stellar feedback not providing
sufficient mixing to quickly flatten gradients. The strongest redshift
evolution occurs in galaxies with stellar masses of
$10^10.0-10^11.0M_odot$, while galaxies with stellar masses $<
10^10M_odot$ and $>10^11M_odot$ exhibit weaker redshift evolution. Our
results of negative gradients at high-redshift contrast with the many positive
and flat gradients in the $1<z<4$ observational literature. At $z>6$, the
negative gradients observed with JWST and ALMA are flatter than those in
simulations, albeit with closer agreement than at lower redshift. Overall, we
suggest that these smooth stellar feedback galaxy simulations may not
sufficiently mix their metal content radially, and that either stronger stellar
feedback or additional subgrid turbulent metal diffusion models may be required
to better reproduce observed metallicity gradients.
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