ZFIRE: Galaxy Cluster Kinematics, H$\alpha$ Star Formation Rates, and
  Gas-Phase Metallicities of XMM-LSS J02182-05102 at z=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
$1.612<z_{\rm spec}<1.635$ defined by 33 members of which 20 are at R$_{\rm
proj}<1$ Mpc. The cluster redshift and velocity dispersion are $z_{\rm
cl}=1.6233\pm0.0003$ and $\sigma_{\rm cl}=254\pm50$ km s$^{-1}$. We reach NIR
line sensitivities of $\sim0.3\times10^{-17}$ erg s$^{-1}$ cm$^{-2}$ that,
combined with multi-wavelength photometry, provide extinction-corrected
H$\alpha$ star formation rates (SFR), gas phase metallicities from
[NII]/H$\alpha$, and stellar masses. We measure an integrated H$\alpha$ SFR of
$\sim325{\rm M}_{\odot}$ yr$^{-1}$ (26 members; R$_{\rm proj}<2$ Mpc) and show
that the elevated star formation in the cluster core (R$_{\rm proj}<0.25$ Mpc)
is driven by the concentration of star-forming members, but the average SFR per
H$\alpha$-detected galaxy is half that of members at R$_{\rm proj}\sim1$ 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 $z\sim0$ and has a slope of
$0.13\pm0.10$. Comparing the MZR in IRC 0218 to the COSMOS cluster at $z=2.1$
shows no evolution ($\Delta t\sim1$ Gyr): the MZR for both galaxy clusters are
remarkably consistent with each other and virtually identical to several field
surveys at $z\sim2$.
