Young, Star-forming Galaxies and Their Local Counterparts: The Evolving Relationship of Mass-SFR-Metallicity Since z ∼ 2.1

Abstract

We explore the evolution of the Stellar Mass-Star Formation Rate (SFR)-Metallicity relation using a set of 256 COSMOS and GOODS galaxies in the redshift range 1.90 < z < 2.35. We present the galaxies’ rest-frame optical emission-line fluxes derived from IR-grism spectroscopy with the Hubble Space Telescope and combine these data with SFRs and stellar masses obtained from deep, multi-wavelength (rest-frame UV to IR) photometry. We then compare these measurements to those for a local sample of galaxies carefully matched in stellar mass (7.5≲ {log}({M}_*/{M}_⊙ )≲ 10.5) and SFR (-0.5≲ {log}({{SFR}})≲ 2.5 in M_⊙ yr^-1). We find that the distribution of z ∼ 2.1 galaxies in stellar mass-SFR-metallicity space is clearly different from that derived for our sample of similarly bright ({L}_{{H}β }\gt 3× {10}⁴⁰ erg s^-1) local galaxies, and this offset cannot be explained by simple systematic offsets in the derived quantities. At stellar masses above ∼ {10}⁹ {M}_⊙ and SFRs above ∼ 10 {M}_⊙ yr^-1, the z ∼ 2.1 galaxies have higher oxygen abundances than their local counterparts, while the opposite is true for lower-mass, lower-SFR systems.