ZFIRE: Galaxy Cluster Kinematics, H alpha Star Formation Rates, and Gas Phase Metallicities of XMM-LSS J02182-05102 at zcl = 1.6232

Abstract

We spectroscopically survey the galaxy cluster XMM-LSS J02182-05102 (hereafter IRC 0218) using LRIS (optical) and MOSFIRE (near-infrared) on Keck I as part of the ZFIRE survey. IRC 0218 has a narrow redshift range of 1.612 \lt {z}_{spec} \lt 1.635 defined by 33 members of which 20 are at R{}_{proj} \lt 1 Mpc. The cluster redshift and velocity dispersion are {z}_{cl}=1.6233+/- 0.0003 and {σ }_{cl}=254+/- 50 km s^-1. We reach NIR line sensitivities of ∼0.3 × 10^-17 erg s^-1 cm^-2 that, combined with multi-wavelength photometry, provide extinction-corrected Hα star formation rates (SFR), gas phase metallicities from [N ii]/Hα, and stellar masses. We measure an integrated Hα SFR of ∼325 {M}_⊙ {{yr}}^-1 (26 members; R{}_{proj} \lt 2 Mpc) and show that the elevated star formation in the cluster core (R{}_{proj} \lt 0.25 Mpc) is driven by the concentration of star-forming members, but the average SFR per Hα-detected galaxy is half that of members at R{}_{proj} ∼ 1 Mpc. However, we do not detect any environmental imprint when comparing attenuation and gas phase metallicities: the cluster galaxies show similar trends with {M}_\star as to the field, e.g., more massive galaxies have larger stellar attenuation. IRC 0218’s gas phase metallicity-{M}_\star relation (MZR) is offset to lower metallicities relative to z∼ 0 and has a slope of 0.13 ± 0.10. Comparing the MZR in IRC 0218 to the COSMOS cluster at z = 2.1 shows no evolution ({{Δ }}t∼ 1 Gyr): the MZR for both galaxy clusters are remarkably consistent with each other and virtually identical to several field surveys at z∼ 2.