Gas inflow and metallicity drops in star-forming galaxies
Abstract
Gas inflow feeds galaxies with low-metallicity gas from the cosmic web, sustaining star formation across the Hubble time. We make a connection between these inflows and metallicity inhomogeneities in star-forming galaxies, by using synthetic narrow-band images of the Hα emission line from zoom-in AMR cosmological simulations of galaxies with stellar masses of M* ≃ 109 M⊙ at redshifts z = 2-7. In ∼50 per cent of the cases at redshifts lower than 4, the gas inflow gives rise to star-forming, Hα-bright, off-centre clumps. Most of these clumps have gas metallicities, weighted by Hα luminosity, lower than the metallicity in the surrounding interstellar medium by ∼0.3 dex, consistent with observations of chemical inhomogeneities at high and low redshifts. Due to metal mixing by shear and turbulence, these metallicity drops are dissolved in a few disc dynamical times. Therefore, they can be considered as evidence for rapid gas accretion coming from cosmological inflow of pristine gas.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- April 2016
- DOI:
- 10.1093/mnras/stw064
- arXiv:
- arXiv:1509.02051
- Bibcode:
- 2016MNRAS.457.2605C
- Keywords:
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- galaxies: evolution;
- galaxies: formation;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 8 pages, 7 figures. New figure 6 and minor changes. Conclusions unchanged. Accepted version