THE FMOS-COSMOS SURVEY OF STAR-FORMING GALAXIES ATz∼ 1.6. II. THE MASS-METALLICITY RELATION AND THE DEPENDENCE ON STAR FORMATION RATE AND DUST EXTINCTION

Abstract

We investigate the relationships between stellar mass, gas-phase oxygen abundance (metallicity), star formation rate, and dust content of star-forming galaxies at z∼1.6 using Subaru/FMOS spectroscopy in the COSMOS field. The mass-metallicity relation at z ∼ 1.6 is steeper than the relation observed in the local Universe. The steeper MZ relation at z ∼ 1.6 is mainly due to evolution in the stellar mass where the MZ relation begins to turnover and flatten. This turnover mass is 1.2 dex larger at z ∼ 1.6. The most massive galaxies at z ∼ 1.6 (∼ 10 11 M ⊙ ) are enriched to the level observed in massive galaxies in the local Universe. The mass-metallicity relation we measure at z ∼ 1.6 supports the suggestion of an empirical upper metallicity limit that does not significantly evolve with redshift. We find an anti-correlation between metallicity and star formation rate for galaxies at a fixed stellar mass at z ∼ 1.6 which is similar to trends observed in the local Universe. We do not find a relation between stellar mass, metallicity and star formation rate that is independent of redshift; our data suggest that there is redshift evolution in this relation. We examine the relation between stellar mass, metallicity and dust extinction. We find that at a fixed stellar mass dustier galaxies tend to be more metal rich. From examination of the stellar masses, metallicities, SFRs and dust extinctions we conclude that stellar mass is most closely related to dust extinction.

Galaxy metallicity scaling relations in the EAGLE simulations

“…The predicted level of evolution at z 1.5 agrees remarkably well with the observed one. At z ≈ 2, the simulation predicts an MZR in good agreement with Zahid et al (2014b) but other observations suggest a higher level of evolution, with the larger discrepancies towards higher M * (e.g. Hunt et al 2016).…”

“…In the following, we summarize briefly the different observational data used here (for more details, the reader is referred to the corresponding papers): de los Reyes et al (2015) (medians and scatter at z ≈ 0.8), Hunt et al (2016) (medians with 75 per cent and 25 per cent quantile levels at 0.4 < z ≤ 0.7, 0.9 < z ≤ 1.8, 1.8 < z ≤ 2.8 and 2.8 < z ≤ 3.8), Ly et al (2016) (medians with the 16th and 84th percentiles at z = 0.5-1.0), Stott et al (2013) (median values and standard errors at z ≈ 0.84-1.47), Yabe et al (2014) (medians and bootstrap errors at z ≈ 1.4), Zahid et al (2014b) (fitted metallicities and observational uncertainties at z ≈ 1.6), Wuyts et al (2016) (mean values and standard errors at z ≈ 0.9 and z ≈ 2.3), Sanders et al (2015) (mean values and uncertainties at z ≈ 2.3), Cullen et al (2014) (fitted metallicities with uncertainties at z 2), Troncoso et al (2014) (individual measurements and their uncertainties at z ≈ 3.4) and Onodera et al (2016) (results from stacking analysis at z ≈ 3.3). Dotted lines in the large four panels indicate the fits to observations at different z given by Maiolino et al (2008).…”

Predicting dust extinction properties of star-forming galaxies from Hα/UV ratio

“…teresting to point out that a small variation (scatter) around the mass-metallicity relation is related to the variation of dust properties of galaxies at fixed stellar mass (see consistent results for high-z galaxies by Zahid et al 2014).…”

The evolution of galaxy metallicity scaling relations in cosmological hydrodynamical simulations

“…Tremonti et al 2004; Lee et al 2006;Kewley & Ellison 2008) but also at higher redshifts up to z ∼ 3.5 (e.g. Savaglio et al 2005;Erb et al 2006;Maiolino et al 2008;Hayashi et al 2009;Lamareille et al 2009;Mannucci et al 2009;Lara-López et al 2010;Moustakas et al 2011;Cresci et al 2012; Yabe et al 2012;Yuan, Kewley & Richard 2013;Zahid et al 2014). Qualitatively speaking, these studies have typically found declining metallicities (at fixed stellar mass) with increasing redshift, although there are quantitative differences in the reported evolution rates.…”

“…Ellison et al 2008;Yabe et al 2014), higher dust fractions (e.g. Zahid et al 2014) and larger B − R and R − H colours (e.g. Yabe et al 2014).…”