Examining a sample of massive galaxies at 1:4 < z < 2:5 with K Vega < 22 from GOODS, we compare photometry from Spitzer at mid-and far-IR to submillimeter, radio, and rest-frame UV wavelengths, to test the agreement between different tracers of star formation rates (SFRs) and to explore the implications for galaxy assembly. For z $ 2 galaxies with moderate luminosities (L 8 m < 10 11 L ), we find that the SFR can be estimated consistently from the multiwavelength data based on local luminosity correlations. However, 20%Y30% of massive galaxies, and nearly all those with L 8 m > 10 11 L , show a mid-IR excess that is likely due to the presence of obscured active nuclei, as shown in a companion paper. There is a tight and roughly linear correlation between stellar mass and SFR for 24 mYdetected galaxies. For a given mass, the SFR at z ¼ 2 was larger by a factor of $4 and $30 relative to that in star-forming galaxies at z ¼ 1 and 0, respectively. Typical ultraluminous infrared galaxies (ULIRGs) at z ¼ 2 are relatively ''transparent'' to ultraviolet light, and their activity is long lived (k400 Myr), unlike that in local ULIRGs and high-redshift submillimeter-selected galaxies. ULIRGs are the common mode of star formation in massive galaxies at z ¼ 2, and the high duty cycle suggests that major mergers are not the dominant trigger for this activity. Current galaxy formation models underpredict the normalization of the mass-SFR correlation by about a factor of 4 and the space density of ULIRGs by an order of magnitude but give better agreement for z > 1:4 quiescent galaxies.

We have studied the properties of giant star forming clumps in five z~2 starforming disks with deep SINFONI AO spectroscopy at the ESO VLT 1 . The clumps reside in disk regions where the Toomre Q-parameter is below unity, consistent with their being bound and having formed from gravitational instability. Broad Hα/ [NII] line wings demonstrate that the clumps are launching sites of powerful outflows. The inferred outflow rates are comparable to or exceed the star formation rates, in one case by a factor of eight. Typical clumps may lose a fraction of their original gas by feedback in a few hundred million years, allowing them to migrate into the center. inferred gas phase oxygen abundance are broadly consistent with inside-out growing disks, and/or with inward migration of the clumps..

This paper presents new deep and wide narrow-band surveys undertaken with UKIRT, Subaru and the VLT; a unique combined effort to select large, robust samples of Hα star-forming galaxies at z = 0.40, 0.84, 1.47 and 2.23 (corresponding to look-back times of 4.2, 7.0, 9.2 and 10.6 Gyrs) in a uniform manner over ∼ 2 deg 2 in the COSMOS and UDS fields. The deep multi-epoch Hα surveys reach a matched 3 σ flux limit of ≈ 3 M yr −1 out to z = 2.2 for the first time, while the wide area and the coverage over two independent fields allow to greatly overcome cosmic variance and assemble by far the largest samples of Hα emitters. Catalogues are presented for a total of 1742, 637, 515 and 807 Hα emitters, robustly selected at z = 0.40, 0.84, 1.47 and 2.23, respectively, and used to determine the Hα luminosity function and its evolution. The faint-end slope of the Hα luminosity function is found to be α = −1.60 ± 0.08 over z = 0 − 2.23, showing no significant evolution. The characteristic luminosity of SF galaxies, L * Hα , evolves significantly as log L * Hα (z) = 0.45z + log L * z=0 . This is the first time Hα has been used to trace SF activity with a single homogeneous survey at z = 0.4−2.23. Overall, the evolution seen with Hα is in good agreement with the evolution seen using inhomogeneous compilations of other tracers of star formation, such as FIR and UV, jointly pointing towards the bulk of the evolution in the last 11 Gyrs being driven by a statistically similar SF population across cosmic time, but with a strong luminosity increase from z ∼ 0 to z ∼ 2.2. Our uniform analysis allows to derive the Hα star formation history of the Universe (SFRH), showing a clear rise up to z ∼ 2.2, for which the simple parametrisation log 10 ρ SFR = −2.1(1 + z) −1 is valid over 80 per cent of the age of the Universe. The results reveal that both the shape and normalisation of the Hα SFRH are consistent with the measurements of the stellar mass density growth, confirming that our Hα SFRH is tracing the bulk of the formation of stars in the Universe for z < 2.23. The star formation activity over the last ∼ 11 Gyrs is responsible for producing ∼ 95 per cent of the total stellar mass density observed locally, with half of that being assembled in 2 Gyrs between z = 1.2-2.2, and the other half in 8 Gyrs (since z < 1.2). If the star-formation rate density continues to decline with time in the same way as seen in the past ∼ 11 Gyrs, then the stellar mass density of the Universe will reach a maximum which is only 5 per cent higher than the present-day value.

We present the KMOS 3D survey, a new integral field survey of over 600 galaxies at 0.7 < z < 2.7 using KMOS at the Very Large Telescope. The KMOS 3D survey utilizes synergies with multi-wavelength ground-and spacebased surveys to trace the evolution of spatially resolved kinematics and star formation from a homogeneous sample over 5 Gyr of cosmic history. Targets, drawn from a mass-selected parent sample from the 3D-HST survey, cover the star formation-stellar mass (M * ) and rest-frame (U − V ) − M * planes uniformly. We describe the selection of targets, the observations, and the data reduction. In the first-year of data we detect Hα emission in 191 M * = 3 × 10 9 -7 × 10 11 M galaxies at z = 0.7-1.1 and z = 1.9-2.7. In the current sample 83% of the resolved galaxies are rotation dominated, determined from a continuous velocity gradient and v rot /σ 0 > 1, implying that the star-forming "main sequence" is primarily composed of rotating galaxies at both redshift regimes. When considering additional stricter criteria, the Hα kinematic maps indicate that at least ∼70% of the resolved galaxies are disk-like systems. Our high-quality KMOS data confirm the elevated velocity dispersions reported in previous integral field spectroscopy studies at z 0.7. For rotation-dominated disks, the average intrinsic velocity dispersion decreases by a factor of two from 50 km s −1 at z ∼ 2.3 to 25 km s −1 at z ∼ 0.9. Combined with existing results spanning z ∼ 0-3, we show that disk velocity dispersions follow an evolution that is consistent with the dependence of velocity dispersion on gas fractions predicted by marginally stable disk theory.