Search

We present accurate photometric redshifts for galaxies observed by the Cluster Lensing And Supernova survey with Hubble (CLASH). CLASH observed 25 massive galaxy cluster cores with the Hubble Space Telescope in 16 filters spanning 0.2-1.7 μm. Photometry in such crowded fields is challenging. Compared to our previously released catalogues, we make several improvements to the photometry, including smaller apertures, intracluster light subtraction, point spread function matching and empirically measured uncertainties. We further improve the Bayesian photometric redshift estimates by adding a redder elliptical template and by inflating the photometric uncertainties of the brightest galaxies. The resulting photometric redshift accuracies are dz/(1+z) ~ 0.8, 1.0 and 2.0 per cent for galaxies with I-band F814W AB magnitudes < 18, 20 and 23, respectively. These results are consistent with our expectations. They improve on our previously reported accuracies by a factor of 4 at the bright end and a factor of 2 at the faint end. Our new catalogue includes 1257 spectroscopic redshifts, including 382 confirmed cluster members. We also provide stellar mass estimates. Finally, we include lensing magnification estimates of background galaxies based on our public lens models. Our new catalogue of all 25 CLASH clusters is available via Mikulski Archive for Space Telescopes. The analysis techniques developed here will be useful in other surveys of crowded fields, including the Frontier Fields and surveys carried out with Javalambre-Physics of the Accelerated Universe Astrophysical Survey and James Webb Space Telescope.© 2017 The Authors., We acknowledge the financial support of the Brazilian funding agency FAPESP (Post-doc fellowship - process number 2014/11806-9). Likewise, we also acknowledge the Spanish Ministerio de Educacion y Ciencia through grant AYA2006-14056 BES-2007-16280. We acknowledge the financial support from the Spanish MICINN under the Consolider-Ingenio 2010 Program grant CSD2006-00070: First Science with the GTC. AM acknowledges the CEFCA (Centro de Estudios de Fisica del Cosmos de Aragon) and the IAA-CSIC (Instituto de Astrofisica de Andalucia) institutes for hosting him during the period 2015/2016. PR, MM, AMe and MN acknowledge the financial support from PRIN-INAF 2014 1.05.01.94.02. Likewise, AMacknowledges the STScI (Space Telescope Science Institute) for hosting him during 2010 AugustSeptember, 2011 June-August and 2016 July. We acknowledge the financial support of ESO since most of the spectroscopic redshifts used in the work were based on ESO VLT programme ID 186.A-0798. BA has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no. 656354.

With the advent of wide-field surveys, cosmology has entered a new golden age of data where our cosmological model and the nature of dark universe will be tested with unprecedented accuracy, so that we can strive for high precision cosmology. Observational probes like weak lensing, galaxy surveys and the cosmic microwave background as well as other observations will all contribute to these advances. These different probes trace the underlying expansion history and growth of structure in complementary ways and can be combined in order to extract cosmological parameters as best as possible. With future wide-field surveys, observational overlap means these will trace the same physical underlying dark matter distribution, and extra care must be taken when combining information from different probes. Consideration of probe combination is a fundamental aspect of cosmostatistics and important to ensure optimal use of future wide-field surveys.

A standard method to study the mass distribution in galaxy clusters is through strong lensing of background galaxies in which the positions of multiple images of the same source constrain the surface mass distribution of the cluster. However, current parametrized mass models can often only reproduce the observed positions to within one or a few arcsec which is worse than the positional measurement uncertainty. One suggested explanation for this discrepancy is the additional perturbations of the path of the light ray caused by matter density fluctuations along the line of sight. We investigate this by calculating the statistical expectation value for the angular deflections caused by density fluctuations, which can be done given the matter power spectrum. We find that density fluctuations can, indeed, produce deflections of a few arcsec. We also find that the deflection angle of a particular image is expected to increase with source redshift and with the angular distance on the sky to the lens. Since the light rays of neighbouring images pass through much the same density fluctuations, it turns out that the images' expected deflection angles can be highly correlated. This implies that line-of-sight density fluctuations are a significant and possibly dominant systematic for strong lensing mass modeling and set a lower limit to how well a cluster mass model can be expected to replicate the observed image positions. We discuss how the deflections and correlations should explicitly be taken into account in the mass model fitting procedure.

Dark matter particles form halos that contribute the major part of the mass of galaxy clusters. The formation of these cosmological structures have been investigated both observationally and in numerical simulations, which have confirmed the existence of a universal mass profile. However, the dynamic behaviour of dark matter in halos is not as well understood. We have used observations of 16 equilibrated galaxy clusters to show that the random velocities of dark matter particles are larger on average along the radial direction than along the tangential, and that the magnitude of this velocity anisotropy is radially varying. Our measurement implies that the collective behaviour of dark matter particles is fundamentally different from that of normal particles and the radial variation of the anisotropy velocity agrees with the predictions of numerical simulation., 5 pages, to appear in the proceedings of the Identification of Dark Matter 2008 conference, Stockholm, Sweden, August 18-22 2008

We demonstrate that all properties of the hot X-ray emitting gas in galaxy clusters are completely determined by the underlying dark matter (DM) structure. Apart from the standard conditions of spherical symmetry and hydrostatic equilibrium for the gas, our proof is based on the Jeans equation for the DM and two simple relations which have recently emerged from numerical simulations: the equality of the gas and DM temperatures, and the almost linear relation between the DM velocity anisotropy profile and its density slope. For DM distributions described by the NFW or the Sersic profiles, the resulting gas density profile, the gas-to-total-mass ratio profile, and the entropy profile are all in good agreement with X-ray observations. All these profiles are derived using zero free parameters. Our result allows us to predict the X-ray luminosity profile of a cluster in terms of its DM content alone. As a consequence, a new strategy becomes available to constrain the DM morphology in galaxy clusters from X-ray observations. Our results can also be used as a practical tool for creating initial conditions for realistic cosmological structures to be used in numerical simulations., 9 pages, 4 figures, including referees comments

The Cluster Lensing And Supernovae survey with Hubble (CLASH) is an Hubble Space Telescope (HST) Multi-Cycle Treasury program observing 25 massive galaxy clusters. CLASH observations are carried out in 16 bands from UV to NIR to derive accurate and reliable estimates of photometric redshifts. We present the CLASH photometric redshifts and study the photometric redshift accuracy of the arcs in more detail for the case of MACS1206.2-0847. We use the publicly available Le Phare and BPZ photometric redshift codes on 17 CLASH galaxy clusters. Using Le Phare code for objects with StoN>=10, we reach a precision of 3%(1+z) for the strong lensing arcs, which is reduced to 2.4%(1+z) after removing outliers. For galaxies in the cluster field the corresponding values are 4%(1+z) and 3%(1+z). Using mock galaxy catalogues, we show that 3%(1+z) precision is what one would expect from the CLASH photometry when taking into account extinction from dust, emission lines and the finite range of SEDs included in the photo-z template library. We study photo-z results for different aperture photometry and find that the SExtractor isophotal photometry works best. Le Phare and BPZ give similar photo-z results for the strong lensing arcs as well as galaxies of the cluster field. Results are improved when optimizing the photometric aperture shape showing an optimal aperture size around 1" radius giving results which are equivalent to isophotal photometry. Tailored photometry of the arcs improve the photo-z results., Accepted in A&A on nov 2013

We present a quintuply lensed z ~ 6 candidate discovered in the field of the galaxy cluster RXC J2248.7-4431 (z ~ 0.348) targeted within the Cluster Lensing and Supernova survey with Hubble (CLASH) and selected in the deep HST Frontier Fields survey. Thanks to the CLASH 16-band HST imaging, we identify the quintuply lensed z ~ 6 candidate as an optical dropout in the inner region of the cluster, the brightest image having magAB=24.81+-0.02 in the f105w filter. We perform a detailed photometric analysis to verify its high-z and lensed nature. We get as photometric redshift z_phot ~ 5.9, and given the extended nature and NIR colours of the lensed images, we rule out low-z early type and galactic star contaminants. We perform a strong lensing analysis of the cluster, using 13 families of multiple lensed images identified in the HST images. Our final best model predicts the high-z quintuply lensed system with a position accuracy of 0.8''. The magnifications of the five images are between 2.2 and 8.3, which leads to a delensed UV luminosity of L_1600 ~ 0.5L*_1600 at z=6. We also estimate the UV slope from the observed NIR colours, finding a steep beta=-2.89+-0.38. We use singular and composite stellar population SEDs to fit the photometry of the hiz candidate, and we conclude that it is a young (age, 21 pages, 13 figures, 6 tables, submitted to MNRAS on 11 Aug 2013, accepted on 23 Nov 2013

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 $z\sim6-8$ galaxies. We report the discovery of 204, 45, and 13 Lyman-break galaxy candidates at $z\sim6$, $z\sim7$, and $z\sim8$, 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 $z\sim 6-8$ 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 $z \gtrsim 6$ candidates. The median magnifications over the 17 clusters are 4, 4, and 5 for the $z\sim6$, $z\sim7$, and $z\sim8$ 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 $\sim27$ 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 $z\sim6$, where we have the best statistics., Comment: Accepted for publication in the Astrophysical Journal, 25 pages, 13 figures, 7 tables

We precisely constrain the inner mass profile of Abell 2261 (z=0.225) for the first time and determine this cluster is not "over-concentrated" as found previously, implying a formation time in agreement with {\Lambda}CDM expectations. These results are based on strong lensing analyses of new 16-band HST imaging obtained as part of the Cluster Lensing and Supernova survey with Hubble (CLASH). Combining this with revised weak lensing analyses of Subaru wide field imaging with 5-band Subaru + KPNO photometry, we place tight new constraints on the halo virial mass M_vir = 2.2\pm0.2\times10^15 M\odot/h70 (within r \approx 3 Mpc/h70) and concentration c = 6.2 \pm 0.3 when assuming a spherical halo. This agrees broadly with average c(M,z) predictions from recent {\Lambda}CDM simulations which span 5

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 CDM. 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, twenty CLASH clusters are solely X-ray selected. The X-ray selected clusters are massive (kT > 5 keV; 5 - 30 x 10^14 M_solar) and, in most cases, dynamically relaxed. Five additional clusters are included for their lensing strength (Einstein radii > 35 arcsec at z_source = 2) to further quantify the lensing bias on concentration, to yield high resolution dark matter maps, and to optimize the likelihood of finding highly magnified high-redshift (z > 7) galaxies. The high magnification, in some cases, provides angular resolutions unobtainable with any current UVOIR facility and can yield z > 7 candidates bright enough for spectroscopic follow-up. 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_phz 1 to improve constraints on the time dependence of the dark energy equation of state and the evolution of such supernovae in an epoch when the universe is matter dominated.

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 $1\la z\la5.5$, 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 $d\log \Sigma/d\log \theta\simeq -0.55\pm 0.1$ (in the range [1\arcsec, 53\arcsec], or $5\la r \la300$ 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 $z_{s}\simeq2.5$, the critical curve encloses a large area with an effective Einstein radius of $\theta_{E}=28\pm3\arcsec$, and a projected mass of $1.34\pm0.15\times10^{14} M_{\odot}$. From the current understanding of structure formation in concordance cosmology, these values are relatively high for clusters at $z\sim0.5$, 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., Comment: 7 pages, 1 table, 4 figures; submitted to ApJ Letters; V3: minor corrections

The distribution of mass in the halos of galaxies and galaxy clusters has been probed observationally, theoretically, and in numerical simulations. Yet there is still confusion about which of several suggested parameterized models is the better representation, and whether these models are universal. We use the temperature and density profiles of the intracluster medium as measured by X-ray observations of 11 relaxed galaxy clusters to investigate mass models for the halo using a thorough Bayesian statistical analysis. We make careful comparisons between two- and three-parameter models, including the issue of a universal third parameter. We find that, of the two-parameter models, the NFW is the best representation, but we also find moderate statistical evidence that a generalized three-parameter NFW model with a freely varying inner slope is preferred, despite penalizing against the extra degree of freedom. There is a strong indication that this inner slope needs to be determined for each cluster individually, i.e. some clusters have central cores and others have steep cusps. The mass-concentration relation of our sample is in reasonable agreement with predictions based on numerical simulations., Comment: 10 pages, 5 figures, accepted by ApJ. Matches accepted version

We consider direct dark matter detection rates and investigate the difference between a standard Maxwell-Boltzmann velocity distribution and a "realistic" distribution like the ones extracted from numerical N-body simulations. Sizable differences are observed when such results are compared to the standard Maxwell-Boltzmann distribution. For a light target both the total rate and the annual modulation are reduced by ~25%. For a heavy target the total rate is virtually unchanged, whereas the annual modulation is modified by up to 50%, depending on the WIMP mass and detector energy threshold. We also consider the effect of a possible velocity anisotropy, and the effect is found to be largest for a light target For the realistic velocity distribution the anisotropy may reduce the annual modulation, in contrast to the Maxwell-Boltzmann case., 13 pages, 10 figures, accepted by Phys. Rev. D

The internal dynamics of a dark matter structure may have the remarkable property that the local temperature in the structure depends on direction. This is parametrized by the velocity anisotropy beta which must be zero for relaxed collisional structures, but has been shown to be non-zero in numerical simulations of dark matter structures. Here we present a method to infer the radial profile of the velocity anisotropy of the dark matter halo in a galaxy cluster from X-ray observables of the intracluster gas. This non-parametric method is based on a universal relation between the dark matter temperature and the gas temperature which is confirmed through numerical simulations. We apply this method to observational data and we find that beta is significantly different from zero at intermediate radii. Thus we find a strong indication that dark matter is effectively collisionless on the dynamical time-scale of clusters, which implies an upper limit on the self-interaction cross-section per unit mass sigma/m < 1 cm2/g. Our results may provide an independent way to determine the stellar mass density in the central regions of a relaxed cluster, as well as a test of whether a cluster is in fact relaxed., 10 pages, 8 figures, submitted to ApJ

Numerous ongoing experiments aim at detecting WIMP dark matter particles from the galactic halo directly through WIMP-nucleon interactions. Once such a detection is established a confirmation of the galactic origin of the signal is needed. This requires a direction-sensitive detector. We show that such a detector can measure the velocity anisotropy beta of the galactic halo. Cosmological N-body simulations predict the dark matter anisotropy to be nonzero, beta~0.2. Baryonic matter has beta=0 and therefore a detection of a nonzero beta would be strong proof of the fundamental difference between dark and baryonic matter. We estimate the sensitivity for various detector configurations using Monte Carlo methods and we show that the strongest signal is found in the relatively few high recoil energy events. Measuring beta to the precision of ~0.03 will require detecting more than 10^4 WIMP events with nuclear recoil energies greater than 100 keV for a WIMP mass of 100 GeV and a 32S target. This number corresponds to ~10^6 events at all energies. We discuss variations with respect to input parameters and we show that our method is robust to the presence of backgrounds and discuss the possible improved sensitivity for an energy-sensitive detector., Comment: 15 pages, 8 figures, accepted by JCAP. Matches accepted version

We utilise a two-color Lyman-Break selection criterion to search for z � 9-10 galaxies over the first 19 clusters in the CLASH program. Key to this search are deep observations over our clusters in five near-IR passbands to 1.6µm, allowing us good constraints on the position of the Lyman break to z � 10. A systematic search yields three z � 9-10 candidates in total above a 6� detection limit. While we have already reported the most robust of these candidates, MACS1149-JD, in a previous publication, two additional z � 9 candidates are also revealed in our expanded search. The new candidates have H160-band AB magnitudes of �26.2-26.9 and are located behind MACSJ1115.9+0129 and MACSJ1720.3+3536. The observed H160 Spitzer/IRAC colors for the sources are sufficiently blue to strongly favor redshifts of z � 9 for these sources. A careful assessment of various sources of contamination suggests .1 contaminants for our z � 9-10 selection. To determine the implications of these search results for the LF and SFR density at z � 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 � 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 � 8. This procedure takes advantage of the fact that the relative selection volumes available for the z � 8 and z � 9-10 selections behind lensing clusters are not greatly dependent on the details of the gravitational lensing models. We find that the normalization of the UV LF at z � 9 is just 0.22 +0.30 −0.15 × that at z � 8, �2 +31× lower than what we would infer extrapolating z � 4-8 LF results. These results therefore suggest a more rapid evolution in the UV LF at z > 8 than seen at lower redshifts (although the current evidence here is weak). Compared to similar evolutionary findings from the HUDF, our result is much more insensitive to large-scale structure uncertainties, given our many independent sightlines on the high-redshift universe. Subject headings: galaxies: evolution — galaxies: high-redshift

We present a candidate for the most distant galaxy known to date with a photometric redshift z = 10.7 +0.6 / -0.4 (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 ~8, 7, and 2, with the brighter two observed at ~26th magnitude AB (~0.15 uJy) in the WFC3/IR F160W filter (~1.4 - 1.7 um) where they are detected at >~ 12-sigma. All three images are also confidently detected at >~ 6-sigma in F140W (~1.2 - 1.6 um), dropping out of detection from 15 lower wavelength HST filters (~0.2 - 1.4 um), and lacking bright detections in Spitzer/IRAC 3.6um and 4.5um imaging (~3.2 - 5.0 um). 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 ~ 10.8 and MACS1149-JD1 at z ~ 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 >~ 10 suggested by field searches., Accepted for publication in the Astrophysical Journal. 23 pages, 18 figures