Artículos de revistas
An Analytical Model for Galaxy Metallicity: What do Metallicity Relations tell us About Star Formation and Outflow?
Fecha
2015-08-01Registro en:
The Astrophysical Journal, 808:129 (9pp), 2015 August 1
doi:10.1088/0004-637X/808/2/129
Autor
Lu, Yu
Blanc Mendiberri, Guillermo
Benson, Andrew
Institución
Resumen
We develop a simple analytical model that tracks galactic metallicities governed by star formation and feedback to
gain insight from the observed galaxy stellar mass–metallicity relations over a large range of stellar masses and
redshifts. The model reveals the following implications of star formation and feedback processes in galaxy
formation. First, the observed metallicity relations provide a stringent upper limit for the averaged outflow massloading
factors of local galaxies, which are ∼20 for M M * 10 ~ 9
galaxies and monotonically decrease to ∼1 for
M M * 10 ~ 11
galaxies. Second, the inferred upper limit for the outflow mass-loading factor sensitively depends
on whether the outflow is metal-enriched with respect to the interstellar medium metallicity. If half of the metals
ejected from supernovae leave the galaxy in metal-enriched winds, the outflow mass-loading factor for galaxies at
any mass can barely be higher than ∼10, which puts strong constraints on galaxy formation models. Third, the
relatively lower stellar-phase to gas-phase metallicity ratio for lower-mass galaxies indicates that low-mass
galaxies are still rapidly enriching their metallicities in recent times, while high-mass galaxies are more settled,
which seems to show a downsizing effect in the metallicity evolution of galaxies. The analysis presented in the
paper demonstrates the importance of accurate measurements of galaxy metallicities and the cold gas fraction of
galaxies at different redshifts for constraining star formation and feedback processes, and demonstrates the power
of these relations for constraining the physics of galaxy formation.