Low Masses and High Redshifts: The Evolution of the Mass-Metallicity Relation

Abstract

We present the first robust measurement of the high redshift mass-metallicity (MZ) relation at 10 8 M/M ⊙ 10 10 , obtained by stacking spectra of 83 emission-line galaxies with secure redshifts between 1.3 z 2.3. For these redshifts, infrared grism spectroscopy with the Hubble Space Telescope Wide Field Camera 3 is sensitive to the R 23 metallicity diagnostic: ([O II] λλ3726, 3729 + [O III] λλ4959, 5007)/Hβ. Using spectra stacked in four mass quartiles, we find a MZ relation that declines significantly with decreasing mass, extending from 12+log(O/H) = 8.8 at M = 10 9.8 M ⊙ , to 12+log(O/H)= 8.2 at M = 10 8.2 M ⊙ . After correcting for systematic offsets between metallicity indicators, we compare our MZ relation to measurements from the stacked spectra of galaxies with M 10 9.5 M ⊙ and z ∼ 2.3. Within the statistical uncertainties, our MZ relation agrees with the z ∼ 2.3 result, particularly since our somewhat higher metallicities (by around 0.1 dex) are qualitatively consistent with the lower mean redshift (z = 1.76) of our sample. For the masses probed by our data, the MZ relation shows a steep slope which is suggestive of feedback from energy-driven winds, and a cosmological downsizing evolution where high mass galaxies reach the local MZ relation at earlier times. In addition, we show that our sample falls on an extrapolation of the star-forming main sequence (the SFR-M * relation) at this redshift. This result indicates that grism emission-line selected samples do not have preferentially high SFRs. Finally, we report no evidence for evolution of the mass-metallicity-SFR plane; our stack-averaged measurements show excellent agreement with the local relation. * Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Characterization of star-forming dwarf galaxies at 0.1 ≲z ≲ 0.9 in VUDS: probing the low-mass end of the mass-metallicity relation

“…Even though the MZR has been well-determined at higher masses (M * > 10 9 M ) (Tremonti et al 2004), it is still not completely defined at lower masses, where it has been studied in the local Universe by Lee et al (2006), Zahid et al (2012b), and Andrews & Martini (2013), but tested at intermediate redshift (z < 1) with relatively small samples (e.g., Henry et al 2013;Ly et al 2014Ly et al , 2015Ly et al , 2016b.…”

“…Thus, the gas-phase metallicity (defined as the oxygen abundance, 12 + log(O/H)) is found to tightly correlate with stellar mass (e.g., Lequeux et al 1979;Tremonti et al 2004) up to high redshift (z ∼ 3.5, e.g., Maiolino et al 2008;Zahid et al 2012a;Cullen et al 2014;Troncoso et al 2014;Onodera et al 2016), with a relatively steep slope flattening above 10 10.5 M . The normalization of this mass-metallicity relation (MZR) appears to evolve to lower metallicities with increasing redshift at fixed stellar mass (Savaglio 2010;Shapley et al 2005;Erb et al 2006;Maiolino et al 2008;Mannucci et al 2009), while the slope, especially in its low-mass end, is still not constrained (e.g., Christensen et al 2012;Henry et al 2013;Whitaker et al 2014;Salim et al 2014). However, both the slope and normalization of the MZR have been found to strongly depend on the method used to derive metallicity (Kewley & Ellison 2008).…”

THE MOSDEF SURVEY: MASS, METALLICITY, AND STAR-FORMATION RATE ATz∼ 2.3

“…Local galaxies follow this relationship with an intrinsic scatter of ∼0.1 dex. The MZR has been confirmed at redshifts up to z ∼ 3.5 and has been observed to evolve with redshift, such that galaxies of a given stellar mass have lower metallicities at higher redshifts (e.g., Erb et al 2006;Maiolino et al 2008;Henry et al 2013;Maier et al 2014;Maseda et al 2014;Steidel et al 2014). The MZR is most commonly understood in terms of the interplay between star formation and gas flows.…”

SPECTROSCOPIC STUDY OF STAR-FORMING GALAXIES IN FILAMENTS AND THE FIELD ATz∼ 0.5: EVIDENCE FOR ENVIRONMENTAL DEPENDENCE OF ELECTRON DENSITY

“…A relatively tight correlation between metallicity and stellar mass (the mass-metallicity relation) has been investigated, with a redshift evolution reflecting the metal enrichment of galaxies over cosmic time (Tremonti et al 2004;Erb et al 2006;Maiolino et al 2008;Foster et al 2012;Xia et al 2012;Henry et al 2013;Sánchez et al 2013;Zahid et al 2013;Masters et al 2014;Steidel et al 2014;Yabe et al 2014;Maier et al 2015;Sanders et al 2015b). It has been shown that this massmetallicity relation originates from a more fundamental mass, metallicity, SFR relation (the fundamental metallicity relation), forming a tight surface in this 3D space (Mannucci et al 2010;Bothwell et al 2013;Lara-López et al 2013a;Stott et al 2013;Maier et al 2014;Nakajima & Ouchi 2014;de los Reyes et al 2015).…”