ZFIRE: GALAXY CLUSTER KINEMATICS, H alpha STAR FORMATION RATES, AND GAS PHASE METALLICITIES OF XMM-LSS J02182-05102 AT z(cl)=1.6233

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 < 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 ±cl = 254 ±50 kms-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 H α star formation rates (SFR), gas phase metallicities from [N II]/Hα, and stellar masses. We measure an integrated H α SFR of ∼325 M⊙yr-1 (26 members; Rproj < 2 Mpc) and show that the elevated star formation in the cluster core (Rproj < 0.25Mpc) is driven by the concentration of star-forming members, but the average SFR per Hα-detected galaxy is half that of members at Rproj ∼ 1Mpc. 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 0218s 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. Show more