We study the evolution of the number density, as a function of the size, of passive early-type galaxies with a wide range of stellar masses (10 10 M ⊙ < M * 10 11.5 M ⊙ ) from z ∼ 3 to z ∼ 1, exploiting the unique dataset available in the GOODS-South field, including the recently obtained WFC3 images as a part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). In particular, we select a sample of ∼107 massive (M * > 10 10 M ⊙ ), passive (SSF R < 10 −2 Gyr −1 ) and morphologically spheroidal galaxies at 1.2 < z < 3, taking advantage of the panchromatic dataset available for GOODS, including VLT, CFHT, Spitzer, Chandra and HST ACS+WFC3 data. We find that at 1 < z < 3 the passively evolving early-type galaxies are the reddest and most massive objects in the Universe, and we prove that a correlation between mass, morphology, color and star-formation activity is already in place at that epoch. We measure a significant evolution in the mass-size relation of passive early-type galaxies (ETGs) from z ∼ 3 to z ∼ 1, with galaxies growing on average by a factor of 2 in size in a 3 Gyr timescale only. We witness also an increase in the number density of passive ETGs of 50 times over the same time interval. We find that the first ETGs to form at z 2 are all compact or ultra-compact, while normal sized ETGs (meaning ETGs with sizes comparable to those of local counterparts of the same mass) are the most common ETGs only at z < 1. The increase of the average size of ETGs at 0 < z < 1 is primarily driven by the appearance of new large ETGs rather than by the size increase of individual galaxies.

We present a 0.4-8 μm multi-wavelength photometric catalog in the Extended Groth Strip (EGS) field. This catalog is built on the Hubble Space Telescope (HST) WFC3 and ACS data from the Cosmic Assembly Nearinfrared Deep Extragalactic Legacy Survey (CANDELS), and it incorporates the existing HST data from the Allwavelength Extended Groth strip International Survey (AEGIS) and the 3D-HST program. The catalog is based on detections in the F160W band reaching a depth of F160W=26.62 AB (90% completeness, point sources). It includes the photometry for 41,457 objects over an area of »206 arcmin 2 in the following bands: HST/ACS F606W and F814W; HST WFC3 F125W, F140W, and F160W; Canada-France-Hawaii Telescope (CFHT)/ Megacam u * , ¢ g , ¢ r , ¢ i and ¢ z ; CFHT/WIRCAM J, H,and K S ; Mayall/NEWFIRM J1, J2, J3, H1, H2, and K; Spitzer IRAC 3.6, 4.5, 5.8, and 8.0 μm. We are also releasing value-added catalogs that provide robust photometric redshifts and stellar mass measurements. The catalogs are publicly available through the CANDELS repository.

We use GOODS and CANDELS images to identify progenitors of massive (M > 10 10 M ⊙ ) compact "early-type" galaxies (ETGs) at z ∼ 1.6. Since merging and accretion increase the size of the stellar component of galaxies, if the progenitors are among known star-forming galaxies, these must be compact themselves. We select candidate progenitors among compact Lyman-break galaxies at z ∼ 3 based on their mass, SFR and central stellar density and find that these account for a large fraction of, and possibly all, compact ETGs at z ∼ 1.6. We find that the average far-UV SED of the candidates is redder than that of the non-candidates, but the optical and mid-IR SED are the same, implying that the redder UV of the candidates is inconsistent with larger dust obscuration, and consistent with more evolved (aging) star-formation. This is in line with other evidence that compactness is a sensitive predictor of passivity among high-redshift massive galaxies. We also find that the light distribution of both the compact ETGs and their candidate progenitors does not show any extended "halos" surrounding the compact "core", both in individual images and in stacks. We argue that this is generally inconsistent with the morphology of merger remnants, even if gas-rich, as predicted by N-body simulations. This suggests that the compact ETGs formed via highly dissipative, mostly gaseous accretion of units whose stellar components are very small and undetected in the HST images, with their stellar mass assembling in-situ, and that they have not experienced any major merging until the epoch of observations at z ∼ 1.6.

We discuss the state of the assembly of the Hubble Sequence in the mix of bright galaxies at redshift 1.4 < z ≤ 2.5 with a large sample of 1,671 galaxies down to H AB ∼ 26, selected from the HST/ACS and WFC3 images of the GOODS-South field obtained as part of the GOODS and CANDELS observations. We investigate the relationship between the star formation properties and morphology using various parametric diagnostics, such as the Sérsic light profile, Gini (G), M 20 , Concentration (C), Asymmetry (A) and multiplicity (Ψ) parameters. Our sample clearly separates into massive, red and passive galaxies versus less massive, blue and star forming ones, and this dichotomy correlates very well with the galaxies' morphological properties. Star-forming galaxies show a broad variety of morphological features, including clumpy structures and bulges mixed with faint low surface brightness features, generally characterized by disky-type light profiles. Passively evolving galaxies, on the other hand, very often have compact light distribution and morphology typical of today's spheroidal systems. We also find that artificially redshifted local galaxies have a similar distribution with z ∼ 2 galaxies in a G-M 20 plane. Visual inspection between the rest-frame optical and UV images show that there is a generally weak morphological k-correction for galaxies at z ∼ 2, but the comparison with non-parametric measures show that galaxies in the rest-frame UV are somewhat clumpier than rest-frame optical. Similar general trends are observed in the local universe among massive galaxies, suggesting that the backbone of the Hubble sequence was already in place at z ∼ 2.

We use the deep CANDELS observations in the GOODS North and South fields to revisit the correlations between stellar mass (M * ), star formation rate (SFR) and morphology, and to introduce a fourth dimension, the massweighted stellar age, in galaxies at < < z 1.2 4. We do this by making new measures of M * , SFR, and stellar age thanks to an improved SED fitting procedure that allows various star formation history for each galaxy. Like others, we find that the slope of the main sequence (MS) of star formation in the * ( ) M ; SFR plane bends at high mass. We observe clear morphological differences among galaxies across the MS, which also correlate with stellar age. At all redshifts, galaxies that are quenching or quenched, and thus old, have high S 1 (the projected density within the central 1 kpc), while younger, star-forming galaxies span a much broader range of S 1 , which includes the high values observed for quenched galaxies, but also extends to much lower values. As galaxies age and quench, the stellar age and the dispersion of S 1 for fixed values of M * shows two different regimes: one at the lowmass end, where quenching might be driven by causes external to the galaxies; the other at the high-mass end, where quenching is driven by internal causes, very likely the mass given the low scatter of S 1 (mass quenching). We suggest that the monotonic increase of central density as galaxies grow is one manifestation of a more general phenomenon of structural transformation that galaxies undergo as they evolve.