ZFIRE: A KECK/MOSFIRE Spectroscopic Survey of Galaxies in Rich Environments at z~2

We present an overview and the first data release of ZFIRE, a spectroscopic redshift survey of star-forming galaxies that utilizes the MOSFIRE instrument on Keck-I to study galaxy properties in rich environments at $1.5<z<2.5$. ZFIRE measures accurate spectroscopic redshifts and basic galaxy properties derived from multiple emission lines. The galaxies are selected from a stellar mass limited sample based on deep near infra-red imaging ($mathrm{K_{AB}<25}$) and precise photometric redshifts from the ZFOURGE and UKIDSS surveys as well as grism redshifts from 3DHST. Between 2013--2015 ZFIRE has observed the COSMOS and UDS legacy fields over 13 nights and has obtained 211 galaxy redshifts over $1.57<z<2.66$ from a combination of nebular emission lines (such as Halpha, NII, Hbeta, OII, OIII, SII) observed at 1--2micron. Based on our medium-band NIR photometry, we are able to spectrophotometrically flux calibrate our spectra to around10% accuracy. ZFIRE reaches $5sigma$ emission line flux limits of around$mathrm{3times10^{-18}~erg/s/cm^2}$ with a resolving power of $R=3500$ and reaches masses down to around10$^{9}$msol. We confirm that the primary input survey, ZFOURGE, has produced photometric redshifts for star-forming galaxies (including highly attenuated ones) accurate to $Delta z/(1+zmathrm{_{spec})}=0.015$ with $0.7%$ outliers. We measure a slight redshift bias of $<0.001$, and we note that the redshift bias tends to be larger at higher masses. We also examine the role of redshift on the derivation of rest-frame colours and stellar population parameters from SED fitting techniques. The ZFIRE survey extends spectroscopically-confirmed $zsim 2$ samples across a richer range of environments, here we make available the first public release of the data for use by the community.footnote{url{http://zfire.swinburne.edu.au}}