2020MNRAS.491.2254W

We present results from deep Spitzer/Infrared Array Camera (IRAC) observations of 28 metal-poor, strongly star-forming galaxies selected from the DEEP2 Galaxy Survey. By modelling infrared and optical photometry, we derive stellar masses and other stellar properties. We determine that these metal-poor galaxies have low stellar masses, M* ≃ 108.1-109.5 M☉. Combined with the Balmer-derived star formation rates (SFRs), these galaxies have average inverse SFR/M* of ≃100 Myr. The evolution of stellar mass-gas metallicity relation to z ≃ 0.8 is measured by combining the modelled masses with previously obtained spectroscopic measurements of metallicity from [O III] λ4363 detections. Here, we include measurements for 79 galaxies from the Metal Abundances across Cosmic Time Survey. Our mass-metallicity relation is lower at a given stellar mass than at z = 0.1 by 0.27 dex. This demonstrates a strong evolution in the mass-metallicity relation, (1+z)^{–1.45{+0.61}_{-0.76}}. We find that the shape of the z ≃ 0.8 mass-metallicity relation, a steep rise in metallicity at low stellar masses, transitioning to a plateau at higher masses, is consistent with z ∼ 0.1 studies. We also compare the evolution in metallicity between z ≃ 0.8 and z ∼ 0.1 against recent strong-line diagnostic studies at intermediate redshifts and find good agreement. Specifically, we find that lower mass galaxies (4 x 108 M☉) built up their metal content 1.6 times more rapidly than higher mass galaxies (1010 M☉). Finally, we examine whether the mass-metallicity relation has a secondary dependence on SFR, and statistically concluded that there is no strong secondary dependence for z ≃ 0.8 low-mass galaxies.