We present a strong-lensing analysis of the galaxy cluster MACS J1206.2-0847 (z = 0.44) using UV, Optical, and IR, HST/ACS/WFC3 data taken as part of the CLASH multi-cycle treasury program, with VLT/VIMOS spectroscopy for some of the multiply lensed arcs. The CLASH observations, combined with our mass model, allow us to identify 47 new multiply lensed images of 12 distant sources. These images, along with the previously known arc, span the redshift range 1 less than or similar to z less than or similar to 5.5, and thus enable us to derive a detailed mass distribution and to accurately constrain, for the first time, the inner mass profile of this cluster. We find an inner profile slope of d log Sigma/d log theta similar or equal to -0.55 +/- 0.1 (in the range [1 '', 53 ''], or 5 kpc less than or similar to r less than or similar to 300 kpc), as commonly found for relaxed and well-concentrated clusters. Using the many systems uncovered here we derive credible critical curves and Einstein radii for different source redshifts. For a source at z(s) similar or equal to 2.5, the critical curve encloses a large area with an effective Einstein radius of theta(E) = 28 '' +/- 3 '', and a projected mass of (1.34 +/- 0.15) x 10(14) M-circle dot. From the current understanding of structure formation in concordance cosmology, these values are relatively high for clusters at z similar to 0.5, so that detailed studies of the inner mass distribution of clusters such as MACS J1206.2-0847 can provide stringent tests of the Lambda CDM paradigm.

The Cluster Lensing And Supernova survey with Hubble (CLASH) is a 524-orbit Multi-Cycle Treasury Program to use the gravitational lensing properties of 25 galaxy clusters to accurately constrain their mass distributions. The survey, described in detail in this paper, will definitively establish the degree of concentration of dark matter in the cluster cores, a key prediction of structure formation models. The CLASH cluster sample is larger and less biased than current samples of space-based imaging studies of clusters to similar depth, as we have minimized lensing-based selection that favors systems with overly dense cores. Specifically, 20 CLASH clusters are solely X-ray selected. The X-ray-selected clusters are massive (kT > 5 keV) and, in most cases, dynamically relaxed. Five additional clusters are included for their lensing strength (theta(Ein) > 35 '' at z(s) = 2) to optimize the likelihood of finding highly magnified high-z (z > 7) galaxies. A total of 16 broadband filters, spanning the near-UV to near-IR, are employed for each 20-orbit campaign on each cluster. These data are used to measure precise (sigma(z) similar to 0.02(1 + z)) photometric redshifts for newly discovered arcs. Observations of each cluster are spread over eight epochs to enable a search for Type Ia supernovae at z > 1 to improve constraints on the time dependence of the dark energy equation of state and the evolution of supernovae. We present newly re-derived X-ray luminosities, temperatures, and Fe abundances for the CLASH clusters as well as a representative source list for MACS1149.6 + 2223 (z = 0.544).

By taking into account the local energy balance per unit volume between the viscous heating and the advective cooling plus the radiative cooling, we investigate the vertical structure of radiation pressure-supported accretion disks in spherical coordinates. Our solutions show that the photosphere of the disk is close to the polar axis and therefore the disk seems to be extremely thick. However, the density profile implies that most of the accreted matter exists in a moderate range around the equatorial plane. We show that the well-known polytropic relation between the pressure and the density is unsuitable for describing the vertical structure of radiation pressure-supported disks. More importantly, we find that the energy advection is significant even for slightly sub-Eddington accretion disks. We argue that the non-negligible advection may help us understand why the standard thin disk model is likely to be inaccurate above similar to 0.3 Eddington luminosity, which was found by some works on black hole spin measurement. Furthermore, the solutions satisfy the Solberg-Hoiland conditions, which indicate the disk to be convectively stable. In addition, we discuss the possible link between our disk model and ultraluminous X-ray sources.

We derive an accurate mass distribution of the galaxy cluster MACS J1206.2-0847 (z = 0.439) from a combined weak-lensing distortion, magnification, and strong-lensing analysis of wide-field Subaru BVR(c)I(c)z' imaging and our recent 16-band Hubble Space Telescope observations taken as part of the Cluster Lensing And Supernova survey with Hubble program. We find good agreement in the regions of overlap between several weak-and strong-lensing mass reconstructions using a wide variety of modeling methods, ensuring consistency. The Subaru data reveal the presence of a surrounding large-scale structure with the major axis running approximately northwest-southeast (NW-SE), aligned with the cluster and its brightest galaxy shapes, showing elongation with a similar to 2:1 axis ratio in the plane of the sky. Our full-lensing mass profile exhibits a shallow profile slope d ln Sigma/d ln R similar to -1 at cluster outskirts (R greater than or similar to 1 Mpc h(-1)), whereas the mass distribution excluding the NW-SE excess regions steepens farther out, well described by the Navarro-Frenk-White form. Assuming a spherical halo, we obtain a virial mass M-vir = (1.1 +/- 0.2 +/- 0.1) x 10(15) M-circle dot h(-1) and a halo concentration c(vir) = 6.9 +/- 1.0 +/- 1.2 (c(vir) similar to 5.7 when the central 50 kpc h(-1) is excluded), which falls in the range 4 less than or similar to < c > less than or similar to 7 of average c(M, z) predictions for relaxed clusters from recent. cold dark matter simulations. Our full-lensing results are found to be in agreement with X-ray mass measurements where the data overlap, and when combined with Chandra gas mass measurements, they yield a cumulative gas mass fraction of 13.7(-3.0)(+4.5)% at 0.7 Mpc h(-1) (approximate to 1.7 r(2500)), a typical value observed for high-mass clusters.

We precisely constrain the inner mass profile of A2261 (z = 0.225) for the first time and determine that this cluster is not "overconcentrated" as found previously, implying a formation time in agreement with Lambda CDM expectations. These results are based on multiple strong-lensing analyses of new 16-band Hubble Space Telescope imaging obtained as part of the Cluster Lensing and Supernova survey with Hubble. Combining this with revised weak-lensing analyses of Subaru wide-field imaging with five-band Subaru + KPNO photometry, we place tight new constraints on the halo virial mass M-vir = (2.2 +/- 0.2) x 10(15) M-circle dot h(70)(-1) (within r(vir) approximate to 3 Mpc h(70)(-1)) and concentration c(vir) = 6.2 +/- 0.3 when assuming a spherical halo. This agrees broadly with average c(M, z) predictions from recent Lambda CDM simulations, which span 5 less than or similar to < c > less than or similar to 8. Our most significant systematic uncertainty is halo elongation along the line of sight (LOS). To estimate this, we also derive a mass profile based on archival Chandra X-ray observations and find it to be similar to 35% lower than our lensing-derived profile at r(2500) similar to 600 kpc. Agreement can be achieved by a halo elongated with a similar to 2:1 axis ratio along our LOS. For this elongated halo model, we find M-vir = (1.7 +/- 0.2) x 10(15) M-circle dot h(70)(-1) and c(vir) = 4.6 +/- 0.2, placing rough lower limits on these values. The need for halo elongation can be partially obviated by non-thermal pressure support and, perhaps entirely, by systematic errors in the X-ray mass measurements. We estimate the effect of background structures based on MMT/Hectospec spectroscopic redshifts and find that these tend to lower M-vir further by similar to 7% and increase c(vir) by similar to 5%.

Hubble Space Telescope images of the galaxy cluster A2261, obtained as part of the Cluster Lensing And Supernova survey with Hubble, show that the brightest galaxy in the cluster, A2261-BCG, has the largest core yet detected in any galaxy. The cusp radius of A2261-BCG is 3.2 kpc, twice as big as the next largest core known, and similar to 3x bigger than those typically seen in the most luminous brightest cluster galaxies. The morphology of the core in A2261-BCG is also unusual, having a completely flat interior surface brightness profile, rather than the typical shallow cusp rising into the center. This implies that the galaxy has a core with constant or even centrally decreasing stellar density. Interpretation of the core as an end product of the "scouring" action of a binary supermassive black hole implies a total black hole mass similar to 10(10) M-circle dot from the extrapolation of most relationships between core structure and black hole mass. The core falls 1 sigma above the cusp radius versus galaxy luminosity relation. Its large size in real terms, and the extremely large black hole mass required to generate it, raises the possibility that the core has been enlarged by additional processes, such as the ejection of the black holes that originally generated the core. The flat central stellar density profile is consistent with this hypothesis. The core is also displaced by 0.7 kpc from the center of the surrounding envelope, consistent with a local dynamical perturbation of the core.

The Carnegie Supernova Project (CSP) is designed to measure the luminosity distance for Type Ia supernovae (SNe Ia) as a function of redshift, and to set observational constraints on the dark energy contribution to the total energy content of the universe. The CSP differs from other projects to date in its goal of providing an I-band rest-frame Hubble diagram. Here, we present the first results from near-infrared observations obtained using the Magellan Baade telescope for SNe Ia with 0.1 < z < 0.7. We combine these results with those from the low-redshift CSP at z < 0.1. In this paper, we describe the overall goals of this long-term program, the observing strategy, data reduction procedures, and treatment of systematic uncertainties. We present light curves and an I-band Hubble diagram for this first sample of 35 SNe Ia, and we compare these data to 21 new SNe Ia at low redshift. These data support the conclusion that the expansion of the universe is accelerating. When combined with independent results from baryon acoustic oscillations, these data yield Omega(m) = 0.27 +/- 0.02( statistical) and Omega(DE) = 0.76 +/- 0.13( statistical) +/- 0.09(systematic), for the matter and dark energy densities, respectively. If we parameterize the data in terms of an equation of state, omega (with no time dependence), assume a flat geometry, and combine with baryon acoustic oscillations, we find that omega = -1.05 +/- 0.13( statistical) +/- 0.09( systematic). The largest source of systematic uncertainty on w arises from uncertainties in the photometric calibration, signaling the importance of securing more accurate photometric calibrations for future supernova cosmology programs. Finally, we conclude that either the dust affecting the luminosities of SNe Ia has a different extinction law (R-V = 1.8) than that in the Milky Way (where R-V = 3.1), or that there is an additional intrinsic color term with luminosity for SNe Ia, independent of the decline rate. Understanding and disentangling these effects is critical for minimizing the systematic uncertainties in future SN Ia cosmology studies.

Re-ionization of the intergalactic medium occurred in the early Universe at redshift z approximate to 6-11, following the formation of the first generation of stars(1). Those young galaxies (where the bulk of stars formed) at a cosmic age of less than about 500 million years (z less than or similar to 10) remain largely unexplored because they are at or beyond the sensitivity limits of existing large telescopes. Understanding the properties of these galaxies is critical to identifying the source of the radiation that re-ionized the intergalactic medium. Gravitational lensing by galaxy clusters allows the detection of high-redshift galaxies fainter than what otherwise could be found in the deepest images of the sky(2). Here we report multiband observations of the cluster MACS J1149+2223 that have revealed (with high probability) a gravitationally magnified galaxy from the early Universe, at a redshift of z = 9.6 +/- 0.2 (that is, a cosmic age of 490 +/- 15 million years, or 3.6 per cent of the age of the Universe). We estimate that it formed less than 200 million years after the Big Bang (at the 95 per cent confidence level), implying a formation redshift of less than or similar to 14. Given the small sky area that our observations cover, faint galaxies seem to be abundant at such a young cosmic age, suggesting that they may be the dominant source for the early re-ionization of the intergalactic medium.

We present a candidate for the most distant galaxy known to date with a photometric redshift of z = 10.7(-0.4)(+0.6) (95% confidence limits; with z < 9.5 galaxies of known types ruled out at 7.2 sigma). This J-dropout Lyman break galaxy, named MACS0647-JD, was discovered as part of the Cluster Lensing and Supernova survey with Hubble (CLASH). We observe three magnified images of this galaxy due to strong gravitational lensing by the galaxy cluster MACSJ0647.7+7015 at z = 0.591. The images are magnified by factors of similar to 80, 7, and 2, with the brighter two observed at similar to 26th magnitude AB (similar to 0.15 mu Jy) in the WFC3/IR F160W filter (similar to 1.4-1.7 mu m) where they are detected at greater than or similar to 12 sigma. All three images are also confidently detected at greater than or similar to 6 sigma in F140W (similar to 1.2- 1.6 mu m), dropping out of detection from 15 lower wavelength Hubble Space Telescope filters (similar to 0.2-1.4 mu m), and lacking bright detections in Spitzer/IRAC 3.6 mu m and 4.5 mu m imaging (similar to 3.2-5.0 mu m). We rule out a broad range of possible lower redshift interlopers, including some previously published as high-redshift candidates. Our high-redshift conclusion is more conservative than if we had neglected a Bayesian photometric redshift prior. Given CLASH observations of 17 high-mass clusters to date, our discoveries of MACS0647-JD at z similar to 10.8 and MACS1149-JD at z similar to 9.6 are consistent with a lensed luminosity function extrapolated from lower redshifts. This would suggest that low-luminosity galaxies could have reionized the universe. However, given the significant uncertainties based on only two galaxies, we cannot yet rule out the sharp drop-off in number counts at z greater than or similar to 10 suggested by field searches.

We present observations of the afterglows and host galaxies of three short-duration gamma-ray bursts (GRBs): 100625A, 101219A, and 110112A. We find that GRB 100625A occurred in a z = 0.452 early-type galaxy with a stellar mass of approximate to 4.6 x 10(9) M-circle dot and a stellar population age of approximate to 0.7 Gyr, and GRB 101219A originated in a star-forming galaxy at z = 0.718 with a stellar mass of approximate to 1.4 x 10(9) M-circle dot, a star formation rate of approximate to 16 M-circle dot yr(-1), and a stellar population age of approximate to 50 Myr. We also report the discovery of the optical afterglow of GRB 110112A, which lacks a coincident host galaxy to i greater than or similar to 26 mag, and we cannot conclusively identify any field galaxy as a possible host. From afterglow modeling, the bursts have inferred circumburst densities of approximate to 10(-4)-1 cm(-3) and isotropic-equivalent gamma-ray and kinetic energies of approximate to 10(50)-10(51) erg. These three events highlight the diversity of galactic environments that host short GRBs. To quantify this diversity, we use the sample of 36 Swift short GRBs with robust associations to an environment (similar to 1/2 of 68 short bursts detected by Swift to 2012 May) and classify bursts originating from four types of environments: late-type (approximate to 50%), early-type (approximate to 15%), inconclusive (approximate to 20%), and "host-less" (lacking a coincident host galaxy to limits of greater than or similar to 26 mag; approximate to 15%). To find likely ranges for the true late- and early-type fractions, we assign each of the host-less bursts to either the late- or early-type category using probabilistic arguments and consider the scenario that all hosts in the inconclusive category are early-type galaxies to set an upper bound on the early-type fraction. We calculate most likely ranges for the late- and early-type fractions of approximate to 60%-80% and approximate to 20%-40%, respectively. We find no clear trend between gamma- ray duration and host type. We also find no change to the fractions when excluding events recently claimed as possible contaminants from the long GRB/collapsar population. Our reported demographics are consistent with a short GRB rate driven by both stellar mass and star formation.