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 reduced data and data products from the 3D-HST survey, a 248-orbit HST Treasury program. The survey obtained WFC3 G141 grism spectroscopy in four of the five CANDELS fields: AEGIS, COSMOS, GOODS-S, and UDS, along with WFC3 H 140 imaging, parallel ACS G800L spectroscopy, and parallel I 814 imaging. In a previous paper, we presented photometric catalogs in these four fields and in GOODS-N, the fifth CANDELS field. Here we describe and present the WFC3 G141 spectroscopic data, again augmented with data from GO-1600 in GOODS-N (PI: B. Weiner). We developed software to automatically and optimally extract interlaced two-dimensional (2D) and one-dimensional (1D) spectra for all objects in the Skelton et al. (2014) photometric catalogs. The 2D spectra and the multi-band photometry were fit simultaneously to determine redshifts and emission line strengths, taking the morphology of the galaxies explicitly into account. The resulting catalog has redshifts and line strengths (where available) for 22,548 unique objects down to  JH 24 IR (79,609 unique objects down to  JH 26 IR ). Of these, 5459 galaxies are at > z 1.5 and 9621 are at < < z 0.7 1.5, where Hα falls in the G141 wavelength coverage. The typical redshift error for  JH 24 IR galaxies is s »´+z 0.003 1 z ( ), i.e., one native WFC3 pixel. The s 3 limit for emission line fluxes of point sources is´-2.1 10 17 erg s −1 cm −2 . All 2D and 1D spectra, as well as redshifts, line fluxes, and other derived parameters, are publicly available.

We study the evolution of the scaling relations that compare the effective density ( r r , e e S < ) and core density ( r , 1 1 S < kpc) to the stellar masses of star-forming galaxies (SFGs) and quiescent galaxies. These relations have been fully in place since z 3 and have exhibited almost constant slope and scatter since that time. For SFGs, the zero points in e S and 1 S decline by only 2 . This fact plus the narrowness of the relations suggests that galaxies could evolve roughly along the scaling relations. Quiescent galaxies follow different scaling relations that are offset to higher densities at the same mass and redshift. Furthermore, the zero point of their core density has declined by only 2 since z 3 , while the zero point of the effective density declines by 10 . When galaxies quench, they move from the star-forming relations to the quiescent relations. This involves an increase in the core and effective densities, which suggests that SFGs could experience a phase of significant core growth relative to the average evolution along the structural relations. The distribution of massive galaxies relative to the SFR-M and the quiescent M  Srelations exhibits an L-shape that is independent of redshift. The knee of this relation consists of a subset of "compact" SFGs that are the most likely precursors of quiescent galaxies forming at later times. The compactness selection threshold in 1 S exhibits a small variation from z=3 to 0.5, M 0.65 log 10.5 9.6 9.3 1 * S --> -( ) M e kpc −2 , allowing the most efficient identification of compact SFGs and quiescent galaxies at every redshift.

We present a systematic study of the shape of the dust attenuation curve in star‐forming galaxies from the far‐ultraviolet (far‐UV) to the near‐infrared (NIR; ∼0.15–2 μ m), as a function of specific star formation rate (ψS) and axial ratio (b/a), for galaxies with and without a significant bulge. Our sample comprises 23 000 (15 000) galaxies with a median redshift of 0.07, with photometric entries in the Sloan Digital Sky Survey (SDSS), UKIRT Infrared Deep Sky Survey‐Large Area Survey and Galaxy Evolution Explorer‐All‐Sky Imaging Survey catalogues and emission‐line measurements from the SDSS spectroscopic survey. We develop a new pair‐matching technique to isolate the dust attenuation curves from the stellar continuum emission. The main results are: (i) the slope of the attenuation curve in the optical varies weakly with ψS, strongly with b/a, and is significantly steeper than the Milky Way extinction law in bulge‐dominated galaxies; (ii) the NIR slope is constant and matches the slope of the Milky Way extinction law; (iii) the UV has a slope change consistent with a dust bump at 2175 Å which is evident in all samples and varies strongly in strength with b/a in the bulge‐dominated sample; (iv) there is a strong increase in emission‐line‐to‐continuum dust attenuation (τV, line/τV, cont) with both decreasing ψS and increasing b/a; and (v) radial gradients in dust attenuation increase strongly with increasing ψS, and the presence of a bulge does not alter the strength of the gradients. These results are consistent with the picture in which young stars are surrounded by dense ‘birth clouds’ with low covering factor which disperse on time‐scales of ∼107 yr and the diffuse interstellar dust is distributed in a centrally concentrated disc with a smaller scaleheight than the older stars that contribute the majority of the red and NIR light. Within this model, the path‐length of diffuse dust, but not of birth‐cloud dust, increases with increasing inclination and the apparent optical attenuation curve is steepened by the differential effect of larger dust opacity towards younger stars than towards older stars. Additionally, our findings suggest that: (i) galaxies with higher star formation rates per unit stellar mass have a higher fraction of diffuse dust, which is more centrally concentrated; (ii) the observed strength of the 2175‐Å dust feature is affected predominantly by global geometry; and (iii) only highly inclined discs are optically thick. We provide new empirically derived attenuation curves for correcting the light from star‐forming galaxies for dust attenuation.