Journal Article

Scaling relations of metallicity, stellar mass and star formation rate in metal-poor starbursts — II. Theoretical models

Laura Magrini, Leslie Hunt, Daniele Galli, Raffaella Schneider, Simone Bianchi, Roberto Maiolino, Donatella Romano, Monica Tosi and Rosa Valiante

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 427, issue 2, pages 1075-1088
Published in print December 2012 | ISSN: 0035-8711
Published online December 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.22055.x
Scaling relations of metallicity, stellar mass and star formation rate in metal-poor starbursts — II. Theoretical models

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Scaling relations of metallicity (O/H), star formation rate (SFR) and stellar mass (Mstar) give important insight on galaxy evolution. They are obeyed by most galaxies in the Local Universe and also at high redshift. In a companion paper, we compiled a sample of ∼1100 galaxies from redshift 0 to ≳3, spanning almost two orders of magnitude in metal abundance, a factor of ∼106 in SFR and of ∼105 in stellar mass. We have characterized empirically the star formation ‘main sequence’ (SFMS) and the mass—metallicity relation (MZR) for this sample, and also identified a class of low-metallicity starbursts, rare locally but more common in the distant Universe. These galaxies deviate significantly from the main scaling relations, with high SFR and low metal content for a given Mstar. In this paper, we model the scaling relations and explain these deviations from them with a set of multi-phase chemical evolution models based on the idea that, independently of redshift, initial physical conditions in a galaxy's evolutionary history can dictate its location in the scaling relations. Our models are able to successfully reproduce the O/H, Mstar and SFR scaling relations up to z ≳ 3, and also successfully predict the molecular cloud fraction as a function of stellar mass. These results suggest that the scaling relations are defined by different modes of star formation: an ‘active’ starburst mode, more common at high redshift, and a quiescent ‘passive’ mode that is predominant locally and governs the main trends.

Keywords: galaxies: abundances; galaxies: dwarf; galaxies: evolution; galaxies: high-redshift; galaxies: starburst; galaxies: star formation

Journal Article.  11321 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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