ZFIRE: GALAXY CLUSTER KINEMATICS, Hα STAR FORMATION RATES, and GAS PHASE METALLICITIES of XMM-LSS J02182-05102 at zcl=1.6233

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 < zspec < 1.635 defined by 33 members of which 20 are at Rproj < 1Mpc. The cluster redshift and velocity dispersion are zcl =  1.6233 0.0003 and scl =  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; Rproj < 2 Mpc) and show that the elevated star formation in the cluster core (Rproj < 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 Rproj ∼ 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 as to the field, e.g., more massive galaxies have larger stellar attenuation. IRC 0218’s gas phase metallicity–M 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 (Dt ~ 1 Gyr): the MZR for both galaxy clusters are remarkably consistent with each other and virtually identical to several field surveys at z ~ 2.