We constrain the slope of the star formation rate (log Ψ) to stellar mass (log M ⋆ ) relation down to log(M ⋆ /M ⊙ ) = 8.4 (log(M ⋆ /M ⊙ ) = 9.2) at z = 0.5 (z = 2.5) with a mass-complete sample of 39,106 star-forming galaxies selected from the 3D-HST photometric catalogs, using deep photometry in the CANDELS fields. For the first time, we find that the slope is dependent on stellar mass, such that it is steeper at low masses (log Ψ ∝ log M ⋆ ) than at high masses (log Ψ ∝ (0.3 − 0.6) log M ⋆ ). These steeper low mass slopes are found for three different star formation indicators: the combination of the ultraviolet (UV) and infrared (IR), calibrated from a stacking analysis of Spitzer/MIPS 24µm imaging; β-corrected UV SFRs; and Hα SFRs. The normalization of the sequence evolves differently in distinct mass regimes as well: for galaxies less massive than log(M ⋆ /M ⊙ ) < 10 the specific SFR (Ψ/M ⋆ ) is observed to be roughly self-similar with Ψ/M ⋆ ∝ (1 + z) 1.9 , whereas more massive galaxies show a stronger evolution with Ψ/M ⋆ ∝ (1 + z) 2.2−3.5 for log(M ⋆ /M ⊙ ) = 10.2 − 11.2. The fact that we find a steep slope of the star formation sequence for the lower mass galaxies will help reconcile theoretical galaxy formation models with the observations.

The 3D-HST and CANDELS programs have provided WFC3 and ACS spectroscopy and photometry over ≈ 900 arcmin 2 in five fields: AEGIS, COSMOS, GOODS-North, GOODS-South, and the UKIDSS UDS field. All these fields have a wealth of publicly available imaging datasets in addition to the HST data, which makes it possible to construct the spectral energy distributions (SEDs) of objects over a wide wavelength range. In this paper we describe a photometric analysis of the CANDELS and 3D-HST HST imaging and the ancillary imaging data at wavelengths 0.3 µm -8 µm. Objects were selected in the WFC3 near-IR bands, and their SEDs were determined by carefully taking the effects of the point spread function in each observation into account. A total of 147 distinct imaging datasets were used in the analysis. The photometry is made available in the form of six catalogs: one for each field, as well as a master catalog containing all objects in the entire survey. We also provide derived data products: photometric redshifts, determined with the EAZY code, and stellar population parameters determined with the FAST code. We make all the imaging data that were used in the analysis available, including our reductions of the WFC3 imaging in all five fields. 3D-HST is a spectroscopic survey with the WFC3 and ACS grisms, and the photometric catalogs presented here constitute a necessary first step in the analysis of these grism data. All the data presented in this paper are available through the 3D-HST website. 16

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.

Spectroscopic+photometric redshifts, stellar mass estimates, and rest-frame colors from the 3D-HST survey are combined with structural parameter measurements from CANDELS imaging to determine the galaxy size-mass distribution over the redshift range 0 < z < 3. Separating early-and late-type galaxies on the basis of star-formation activity, we confirm that early-type galaxies are on average smaller than late-type galaxies at all redshifts, and we find a significantly different rate of average size evolution at fixed galaxy mass, with fast evolution for the early-type population, R eff ∝ (1 + z) −1.48 , and moderate evolution for the late-type population, R eff ∝ (1 + z) −0.75 . The large sample size and dynamic range in both galaxy mass and redshift, in combination with the high fidelity of our measurements due to the extensive use of spectroscopic data, not only fortify previous results, but also enable us to probe beyond simple average galaxy size measurements. At all redshifts the slope of the size-mass relation is shallow, R eff ∝ M 0.22 * , for late-type galaxies with stellar mass > 3 × 10 9 M , and steep, R eff ∝ M 0.75 * , for early-type galaxies with stellar mass > 2 × 10 10 M . The intrinsic scatter is 0.2 dex for all galaxy types and redshifts. For late-type galaxies, the logarithmic size distribution is not symmetric but is skewed toward small sizes: at all redshifts and masses a tail of small late-type galaxies exists that overlaps in size with the early-type galaxy population. The number density of massive (∼ 10 11 M ), compact (R eff < 2kpc) early-type galaxies increases from z = 3 to z = 1.5 − 2 and then strongly decreases at later cosmic times.