The FourStar galaxy evolution survey (ZFOURGE) is a 45 night legacy program with the FourStar near-infrared camera on Magellan and one of the most sensitive surveys to date. ZFOURGE covers a total of 400 arcmin 2 in cosmic fields CDFS, COSMOS and UDS, overlapping CANDELS. We present photometric catalogs comprising > 70, 000 galaxies, selected from ultradeep K s -band detection images (25.5 − 26.5 AB mag, 5σ, total), and > 80% complete to K s < 25.3 − 25.9 AB. We use 5 near-IR medium-bandwidth filters (J 1 , J 2 , J 3 , H s , H l ) as well as broad-band K s at 1.05 − 2.16 µm to 25 − 26 AB at a seeing of ∼ 0.′′ 5. Each field has ancillary imaging in 26 − 40 filters at 0.3 − 8 µm. We derive photometric redshifts and stellar population properties. Comparing with spectroscopic redshifts indicates a photometric redshift uncertainty σ z = 0.010, 0.009, and 0.011 in CDFS, COSMOS, and UDS. As spectroscopic samples are often biased towards bright and blue sources, we also inspect the photometric redshift differences between close pairs of galaxies, finding σ z,pairs = 0.01 − 0.02 at 1 < z < 2.5. We quantify how σ z,pairs depends on redshift, magnitude, SED type, and the inclusion of FourStar medium bands. σ z,pairs is smallest for bright, blue star-forming samples, while red starforming galaxies have the worst σ z,pairs . Including FourStar medium bands reduces σ z,pairs by 50% at 1.5 < z < 2.5. We calculate SFRs based on ultraviolet and ultradeep far-IR Spitzer/MIPS and Herschel/PACS data. We derive rest-frame U − V and V − J colors, and illustrate how these correlate with specific SFR and dust emission to z = 3.5. We confirm the existence of quiescent galaxies at z ∼ 3, demonstrating their SFRs are suppressed by > ×15.

We present an overview and the first data release of ZFIRE, a spectroscopic redshift survey of starforming 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 infrared imaging (K AB < 25) and precise photometric redshifts from the ZFOURGE and UKIDSS surveys as well as grism redshifts from 3DHST. Between 2013 and 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 Hα, [Nii], Hβ, [Sii]) observed at 1-2µm. Based on our medium-band near infra-red photometry, we are able to spectrophotometrically flux calibrate our spectra to ∼10% accuracy. ZFIRE reaches 5σ emission line flux limits of ∼3 × 10 −18 erg/s/cm 2 with a resolving power of R = 3500 and reaches masses down to ∼10 9 M . We confirm that the primary input survey, ZFOURGE, has produced photometric redshifts for star-forming galaxies (including highly attenuated ones) accurate to ∆z/(1+ z 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 z ∼ 2 samples across a richer range of environments, here we make available the first public release of the data for use by the community. a

We investigate the star formation rate (SFR) dependence on the stellar mass and gas-phase metallicity relation at z = 2 with MOSFIRE/Keck as part of the ZFIRE survey. We have identified 117 galaxies (1.98≤ z ≤2.56), with 8.9 ≤log(M/M ⊙ )≤ 11.0, for which we can measure gas-phase metallicities. For the first time, we show discernible difference between the mass-metallicity relation, using individual galaxies, when deviding the sample by low (< 10 M ⊙ yr −1 ) and high (> 10 M ⊙ yr −1 ) SFRs. At fixed mass, low star-forming galaxies tend to have higher metallicity than high star-forming galaxies. Using a few basic assumptions, we further show that the gas masses and metallicities required to produce the fundamental mass-metallicity relation, and its intrinsic scatter, are consistent with cold-mode accretion predictions obtained from the OWLS hydrodynamical simulations. Our results from both simulations and observations are suggestive that cold-mode accretion is responsible for the fundamental mass-metallicity relation at z = 2 and demonstrates the direct relationship between cosmological accretion and the fundamental properties of galaxies.