Cold-mode accretion: Driving the fundamental mass-metallicity relation at z ∼ 2
Glenn G. Kacprzak, Freeke van de Voort, Karl Glazebrook, Kim‐Vy Tran, Tiantian Yuan, Themiya Nanayakkara, Rebecca Allen, Leo Y. Alcorn, Michael J. Cowley, Ivo Labbé, Lee R. Spitler, Caroline M. S. Straatman, Adam Tomczak
Abstract
We investigate the star formation rate (SFR) dependence on the stellar mass and gas-phase metallicity relation at z = 2 with MOSFIRE/Keck as part of the ZFIRE survey. We have identified 117 galaxies (1.98 ≤ z ≤ 2.56), with 8.9 ≤ log(M/M ⊙) ≤ 11.0, for which we can measure gas-phase metallicities. For the first time, we show a discernible difference between the mass–metallicity relation, using individual galaxies, when dividing the sample by low (<10 M ⊙ yr−1) and high (>10 M ⊙ yr−1) SFRs. At fixed mass, low star-forming galaxies tend to have higher metallicity than high star-forming galaxies. Using a few basic assumptions, we further show that the gas masses and metallicities required to produce the fundamental mass–metallicity relation and its intrinsic scatter are consistent with cold-mode accretion predictions obtained from the OWLS hydrodynamical simulations. Our results from both simulations and observations are suggestive that cold-mode accretion is responsible for the fundamental mass–metallicity relation at z = 2 and it demonstrates the direct relationship between cosmological accretion and the fundamental properties of galaxies.