The physics of the fundamental metallicity relation

Pratika Dayal, Andrea Ferrara, James S. Dunlop

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We present a simple, redshift-independent analytic model that explains the local fundamental metallicity relation (FMR), taking into account the physical processes of star formation, inflow of metal-poor intergalactic medium (IGM) gas, and the outflow of metal-rich interstellar medium (ISM) gas. We show that the physics of the FMR can be summarized as follows: for massive galaxies with stellar mass M* ≥ 1011 M, ISM metal enrichment due to star formation is compensated by inflow of metal-poor IGM gas, leading to a constant value of the gas metallicity with star formation rate (SFR); outflows are rendered negligible as a result of the large potential wells of these galaxies. On the other hand, as a result of their smaller SFR, less massive galaxies produce less heavy elements that are also more efficiently ejected due to their shallow potential wells; as a result, for a given M*, the gas metallicity decreases with SFR. For such galaxies, the outflow efficiency determines both the slope and the knee of the metallicity-SFR relation. Without changing any parameters, this simple model is also successfully matched to the gas fraction-gas metallicity relation observed for a sample of about 260 nearby galaxies.
Original languageEnglish
Pages (from-to)2891-2895
Number of pages5
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
Publication statusPublished - 1-Apr-2013
Externally publishedYes


  • galaxies: abundances
  • galaxies: evolution
  • galaxies: fundamental parameters
  • galaxies: high-redshift
  • galaxies: stellar content
  • Astrophysics - Cosmology and Nongalactic Astrophysics

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