Aims: We constrain the mass, velocity-anisotropy, and pseudo-phase-space density profiles of the z = 0.44 CLASH cluster MACS J1206.2-0847, using the projected phase-space distribution of cluster galaxies in combination with gravitational lensing.

We present VIsible Multi-Object Spectrograph (VIMOS) observations of a z similar to 6 galaxy quintuply imaged by the Frontier Fields galaxy cluster RXC J2248.7-4431 (z = 0.348). This sub-L*, high-z galaxy has been recently discovered by Monna et al. (2013) using dropout techniques with the 16-band HST photometry acquired as part of the Cluster Lensing And Supernova survey with Hubble (CLASH). Obtained as part of the CLASH-VLT survey, the VIMOS medium-resolution spectra of this source show a very faint continuum between similar to 8700 angstrom and similar to 9300 angstrom and a prominent emission line at 8643 angstrom, which can be readily identified with Lyman-alpha at z = 6.110 +/- 0.002. The emission line exhibits an asymmetric profile, with a more pronounced red wing. The rest-frame equivalent width of the line is EW = 79 +/- 10 angstrom, relatively well constrained thanks to the detection of the UV continuum, which is rarely achieved for a sub-L* galaxy at this redshift. After correcting for magnification, the star formation rate (SFR) estimated from the Ly alpha line is SFR(Ly alpha) = 11 M-circle dot yr(-l) and that estimated from the UV data is SFR(UV) = 3 M-circle dot yr(-1). We estimate that the effective radius of the source is R-e less than or similar to 0.4 kpc, which implies a star formation surface mass density Sigma(SFR) > 6 M(circle dot)yr(-1) kpc(-2) and, using the Kennicutt-Schmidt relation, a gas surface mass density Sigma(gas) > 10(3) M(circle dot)pc(-2). Our results support the idea that this magnified, distant galaxy is a young and compact object with luminosity 0.4 L* at z = 6, when the Universe was just 1 Gyr old, with a similar amount of mass in gas and stars. In the spirit of the Frontier Fields initiative, we also publish the redshifts of several multiply imaged sources and other background objects, which will help improving the strong-lensing model of this galaxy cluster.

We utilize 16 band Hubble Space Telescope (HST) observations of 18 lensing clusters obtained as part of the Cluster Lensing And Supernova survey with Hubble (CLASH) Multi-Cycle Treasury program to search for z similar to 6-8 galaxies. We report the discovery of 204, 45, and 13 Lyman-break galaxy candidates at z similar to 6, z similar to 7, and z similar to 8, respectively, identified from purely photometric redshift selections. This large sample, representing nearly an order of magnitude increase in the number of magnified star-forming galaxies at z similar to 6-8 presented to date, is unique in that we have observations in four WFC3/UVIS UV, seven ACS/WFC optical, and all five WFC3/IR broadband filters, which enable very accurate photometric redshift selections. We construct detailed lensing models for 17 of the 18 clusters to estimate object magnifications and to identify two new multiply lensed z greater than or similar to 6 candidates. The median magnifications over the 17 clusters are 4, 4, and 5 for the z similar to 6, z similar to 7, and z similar to 8 samples, respectively, over an average area of 4.5 arcmin(2) per cluster. We compare our observed number counts with expectations based on convolving "blank" field UV luminosity functions through our cluster lens models and find rough agreement down to similar to 27 mag, where we begin to suffer significant incompleteness. In all three redshift bins, we find a higher number density at brighter observed magnitudes than the field predictions, empirically demonstrating for the first time the enhanced efficiency of lensing clusters over field surveys. Our number counts also are in general agreement with the lensed expectations from the cluster models, especially at z 6, where we have the best statistics.

Context. The Cluster Lensing And Supernovae survey with Hubble (CLASH) is a Hubble Space Telescope (HST) Multi-Cycle Treasury programme that observes 25 massive galaxy clusters, 20 of which were X-ray-selected to preferably choose dynamically relaxed clusters, and 5 additional "high magnification" clusters, which were selected based on their optical lensing properties. CLASH aims to study the dark matter distribution of the clusters and find magnified high-redshift galaxies behind them. CLASH observations were carried out in 16 bands from UV to NIR to derive accurate and reliable estimates of photometric redshifts.

The deflection angles of lensed sources increase with their distance behind a given lens. We utilize this geometric effect to corroborate the z(phot) similar or equal to 9.8 photometric redshift estimate of a faint near-IR dropout, triply imaged by the massive galaxy cluster A2744 in deep Hubble Frontier Fields images. The multiple images of this source follow the same symmetry as other nearby sets of multiple images that bracket the critical curves and have well-defined redshifts (up to z(spec) similar or equal to 3.6), but with larger deflection angles, indicating that this source must lie at a higher redshift. Similarly, our different parametric and non-parametric lens models all require this object be at z greater than or similar to 4, with at least 95% confidence, thoroughly excluding the possibility of lower-redshift interlopers. To study the properties of this source, we correct the two brighter images for their magnifications, leading to a star formation rate of similar to 0.3M(circle dot) yr(-1), a stellar mass of similar to 4 x 10(7) M-circle dot, and an age of less than or similar to 220 Myr (95% confidence). The intrinsic apparent magnitude is 29.9 AB (F160W), and the rest-frame UV (similar to 1500 angstrom) absolute magnitude is M-UV,M-AB = -17.6. This corresponds to similar to 0.1L(z=8)(*) (similar to 0.2 L-z=10(*), adopting dM(*)/dz similar to 0.45), making this candidate one of the least luminous galaxies discovered at z similar to 10.

Aims. We aim constrain the assembly history of clusters by studying the intracluster light (ICL) properties, estimating its contribution to the fraction of baryons in stars, f(*), and understanding possible systematics or bias using different ICL detection techniques.

We utilize a two-color Lyman-break selection criterion to search for z similar to 9-10 galaxies over the first 19 clusters in the CLASH program. A systematic search yields three z similar to 9-10 candidates. While we have already reported the most robust of these candidates, MACS1149-JD, two additional z similar to 9 candidates are also found and have H-160- band magnitudes of similar to 26.2-26.9. A careful assessment of various sources of contamination suggests less than or similar to 1 contaminants for our z similar to 9-10 selection. To determine the implications of these search results for the luminosity function (LF) and star formation rate density at z similar to 9, we introduce a new differential approach to deriving these quantities in lensing fields. Our procedure is to derive the evolution by comparing the number of z similar to 9-10 galaxy candidates found in CLASH with the number of galaxies in a slightly lower-redshift sample (after correcting for the differences in selection volumes), here taken to be z similar to 8. This procedure takes advantage of the fact that the relative volumes available for the z similar to 8 and z similar to 9-10 selections behind lensing clusters are not greatly dependent on the details of the lensing models. We find that the normalization of the UV LF at z similar to 9 is just 0.28(-0.20)(+0.39) x that at z similar to 8, which is similar to 1.4(-0.8)(+3.0) x lower than extrapolating z similar to 4-8 LF results. While consistent with the evolution in the UV LF seen at z similar to 4-8, these results marginally favor a more rapid evolution at z > 8. Compared to similar evolutionary findings from the HUDF, our result is less insensitive to large-scale structure uncertainties, given our many independent sightlines on the high-redshift universe.

We report the discovery of 24 Lyman-break candidates at 7 less than or similar to z less than or similar to 10.5, in the Hubble Frontier Fields (HFF) imaging data of A2744 (z = 0.308), plus Spitzer/IRAC data and archival ACS data. The sample includes a triple image system with a photometric redshift of z similar or equal to 7.4. This high redshift is geometrically confirmed by our lens model corresponding to deflection angles that are 12% larger than the lower-redshift systems used to calibrate the lens model at z = 2.019. The majority of our high-redshift candidates are not expected to be multiply lensed given their locations in the image plane and the brightness of foreground galaxies, but are magnified by factors of similar to 1.3-15, so that we are seeing further down the luminosity function than comparable deep-field imaging. It is apparent that the redshift distribution of these sources does not smoothly extend over the full redshift range accessible at z < 12, but appears to break above z = 9. Nine candidates are clustered within a small region of 20 '' across, representing a potentially unprecedented concentration. Given the poor statistics, however, we must await similar constraints from the additional HFF clusters to properly examine this trend. The physical properties of our candidates are examined using the range of lens models developed for the HFF program by various groups including our own, for a better estimate of underlying systematics. Our spectral-energy-distribution fits for the brightest objects suggest stellar masses of similar or equal to 10(9) M-circle dot, star formation rates of similar or equal to 4 M-circle dot yr(-1), and a typical formation redshift of z less than or similar to 19.

We present an analysis of the MUSIC-2 N-body/hydrodynamical simulations aimed at estimating the expected concentration-mass relation for the CLASH (Cluster Lensing and Supernova Survey with Hubble) cluster sample. We study nearly 1,400 halos simulated at high spatial and mass resolution. We study the shape of both their density and surface-density profiles and fit them with a variety of radial functions, including the Navarro-Frenk-White (NFW), the generalized NFW, and the Einasto density profiles. We derive concentrations and masses from these fits. We produce simulated Chandra observations of the halos, and we use them to identify objects resembling the X-ray morphologies and masses of the clusters in the CLASH X-ray-selected sample. We also derive a concentration-mass relation for strong-lensing clusters. We find that the sample of simulated halos that resembles the X-ray morphology of the CLASH clusters is composed mainly of relaxed halos, but it also contains a significant fraction of unrelaxed systems. For such a heterogeneous sample we measure an average two-dimensional concentration that is similar to 11% higher than is found for the full sample of simulated halos. After accounting for projection and selection effects, the average NFW concentrations of CLASH clusters are expected to be intermediate between those predicted in three dimensions for relaxed and super-relaxed halos. Matching the simulations to the individual CLASH clusters on the basis of the X-ray morphology, we expect that the NFW concentrations recovered from the lensing analysis of the CLASH clusters are in the range [3-6], with an average value of 3.87 and a standard deviation of 0.61.

We present results on the stellar population properties of massive galaxies at z = 0.7 based on deep, medium-resolution IMACS spectra for a sample of similar to 70 galaxies in the ECDFS with M-* > 10(10) M-circle dot. The age-mass and stellar metallicity-mass relations for the population as a whole have a similar shape as the local relations over the probed mass range, but offset to ages younger by similar to 4 Gyr and metallicities lower by similar to 0.13 dex. Quiescent galaxies alone have stellar ages and metallicities consistent with passive evolution onto the local quiescent galaxies relations. The evolution in metallicity is driven by star-forming galaxies. However a significant fraction of massive star-forming galaxies have metallicities comparable to those of local quiescent galaxies. If quenched at z < 0.7 they can provide the necessary population to reproduce the scatter in age and metallicity of local quiescent galaxies.