The evolution of the oxygen abundance gradients in star-forming galaxies in the EAGLE simulations

TISSERA, P. B.; ROSAS-GUEVARA, Y.; SILLERO, E.; PEDROSA, S. E.; THEUNS, T.; BIGNONE, L.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2022

0035-8711

We analyse the evolution of the oxygen abundance gradient of star-forming galaxies withstellar mass, M∗ ≥ 109M⊙, in the eagle simulation over the redshift range 𝑧 = [0, 2.5].We find that the median metallicity gradient of the simulated galaxies is close to zero atall 𝑧, whereas the scatter around the median increases with 𝑧. The metallicity gradients ofindividual galaxies can evolve from strong to weak gradients and vice-versa, as mostly lowmetallicity gas accretes onto the galaxy resulting in enhanced star formation and ejectionof metal enriched gas by energy feedback. Such episodes of enhanced accretion, mainlydominated by major mergers, are more common at higher 𝑧, and hence contribute to increasingthe diversity of gradients. For galaxies with negative metallicity gradients, we find a redshiftevolution of ∼ −0.03 dex kpc−1/𝛿z. A positive mass dependence is found at 𝑧 ≤ 0.5, whichbecomes slightly stronger for higher redshifts, and mainly, for M∗ < 109.5M⊙. Only galaxieswith negative metallicity gradients define a correlation with galaxy size, consistent with aninside-out formation scenario. Our findings suggest that major mergers and/or significantgas accretion can drive strong negative or positive metallicity gradients. The first ones arepreferentially associated with disc-dominated galaxies and the second one, with dispersiondominated ones. The comparison with forthcoming observations at high redshift will allow abetter understanding of the potential role of metallicity gradients as a chemical benchmark ofgalaxy formation.