We present an analysis of the MUSIC-2 /V-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 (NEW), the generalized NEW, 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 ~11% higher than is found for the full sample of simulated halos. After accounting for projection and selection effects, the average NEW 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 NEW 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.
Abstract
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.
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 <, ~ z <, ~ 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 capital sigma /d log theta Asymptotically = to -0.55 + or - 0.1 (in the range 1", 53", or 5 kpc <, ~ r <, ~ 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 sub(s) Asymptotically = to 2.5, the critical curve encloses a large area with an effective Einstein radius of theta sub(E) = 28" + or - 3", and a projected mass of (1.34 + or - 0.15) x 10 super(14) M in . From the current understanding of structure formation in concordance cosmology, these values are relatively high for clusters at z ~ 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 LambdaCDM paradigm.
Abstract
We perform an analysis of photometric redshifts estimated by using a non-representative training sets in magnitude space. We use the ANNz2 and GPz algorithms to estimate the photometric ...redshift both in simulations and in real data from the Sloan Digital Sky Survey (DR12). We show that for the representative case, the results obtained by using both algorithms have the same quality, using either magnitudes or colours as input. In order to reduce the errors when estimating the redshifts with a non-representative training set, we perform the training in colour space. We estimate the quality of our results by using a mock catalogue which is split samples cuts in the r band between 19.4 < r < 20.8. We obtain slightly better results with GPz on single point z-phot estimates in the complete training set case, however the photometric redshifts estimated with ANNz2 algorithm allows us to obtain mildly better results in deeper r-band cuts when estimating the full redshift distribution of the sample in the incomplete training set case. By using a cumulative distribution function and a Monte Carlo process, we manage to define a photometric estimator which fits well the spectroscopic distribution of galaxies in the mock testing set, but with a larger scatter. To complete this work, we perform an analysis of the impact on the detection of clusters via density of galaxies in a field by using the photometric redshifts obtained with a non-representative training set.
The Sloan Digital Sky Survey IV extended Baryonic Oscillation Spectroscopic Survey (SDSS-IV/eBOSS) will observe 195 000 emission-line galaxies (ELGs) to measure the baryonic acoustic oscillation ...(BAO) standard ruler at redshift 0.9. To test different ELG selection algorithms, 9000 spectra were observed with the SDSS spectrograph as a pilot survey based on data from several imaging surveys. First, using visual inspection and redshift quality flags, we show that the automated spectroscopic redshifts assigned by the pipeline meet the quality requirements for a reliable BAO measurement. We also show the correlations between sky emission, signal-to-noise ratio in the emission lines, and redshift error. Then we provide a detailed description of each target selection algorithm we tested and compare them with the requirements of the eBOSS experiment. As a result, we provide reliable redshift distributions for the different target selection schemes we tested. Finally, we determine an target selection algorithms that is best suited to be applied on DECam photometry because they fulfill the eBOSS survey efficiency requirements.
We present two wide-field catalogues of photometrically selected emission line galaxies (ELGs) at z ... 0.8 covering about 2800 deg super( 2) over the south galactic cap. The catalogues were obtained ...using a Fisher discriminant technique described in a companion paper. The two catalogues differ by the imaging used to define the Fisher discriminant: the first catalogue includes imaging from the Sloan Digital Sky Survey and the Wide-field Infrared Survey Explorer, the second also includes information from the South Galactic Cap U-band Sky Survey. Containing respectively 560 045 and 615 601 objects, they represent the largest ELG catalogues available today and were designed for the ELG programme of the extended Baryon Oscillation Spectroscopic Survey (eBOSS). We study potential sources of systematic variation in the angular distribution of the selected ELGs due to fluctuations of the observational parameters. We model the influence of the observational parameters using a multivariate regression and implement a weighting scheme which allows effective removal of all of the systematic errors induced by the observational parameters. We show that fluctuations in the imaging zero-points of the photometric bands have minor impact on the angular distribution of objects in our catalogues. We compute the angular clustering of both catalogues and show that our weighting procedure effectively removes spurious clustering on large scales. We fit a model to the small-scale angular clustering, showing that the selections have similar biases of 1.35/D sub( a)(z) and 1.28/D sub( a)(z). Both catalogues are publicly available. (ProQuest: ... denotes formulae/symbols omitted.)
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 Hubble Space Telescope (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 = 24.8 ± 0.1 in the f105w filter. We perform a detailed photometric analysis to verify its high-z and lensed nature. We get as photometric redshift z
ph ∼ 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 arcsec. The magnifications of the five images are between 2.2 and 8.3, which leads to a delensed UV luminosity of
$L_{1600}\sim 0.5L_{1600}^*$
at z = 6. We also estimate the UV slope from the observed NIR colours, finding a steep β = −2.89 ± 0.38. We use singular and composite stellar population SEDs to fit the photometry of the high-z candidate, and we conclude that it is a young (age <300 Myr) galaxy with mass of M ∼ 108 M⊙, subsolar metallicity (Z < 0.2 Z⊙) and low dust content (A
V
∼ 0.2–0.4).
Context. The Cluster Lensing And Supernovae survey with Hubble (CLASH) is a Hubble Space Telescope (HST) Multi-Cycle Treasury programme thatobserves 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. Aims. We present the CLASH photometric redshifts using 16 HST bands and study the photometric redshift accuracy including a detailed comparison between photometric and spectroscopic redshifts for the strong lensing arcs using the measurements from the cluster MACSJ1206.2-0847. Methods. We used the publicly available Le Phare and BPZ photometric redshift estimation codes on 17 CLASH galaxy clusters for which the full photo-z data processing had been completed at the time of this analysis, and derive an estimate of the CLASH photo-z accuracy. Results. Using Le Phare code for objects with a S/N ≥ 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 is expected using the baseline sky substraction algorithm when taking into account extinction from dust, emission lines, and the finite range of SEDs included in the photo-z template library. An improved method for estimating galaxy colours that yields more accurate photometric redshifts will be explored in a forthcoming paper. We study photo-z results for different aperture photometry techniques and find that the SExtractor isophotal photometry works best. We check the robustness of the arcs photo-z results by rederiving the input photometry in the case of MACS1206. We describe and release a photometric redshift catalogue of the MACS1206 cluster we study. Conclusions. Our photo-z codes give similar results for the strong lensing arcs, as well as for galaxies of the cluster field. Results are improved when optimizing the photometric aperture shape that shows an optimal aperture size around 1′′ radius, giving results that are equivalent to isophotal photometry. Tailored photometry of the arcs improves the photo-z results by showing more consistency between the different arcs of the same strong lensing system.
We examine the inner mass distribution of the relaxed galaxy cluster A383 (z = 0.189), in deep 16 band Hubble Space Telescope/ACS+WFC3 imaging taken as part of the Cluster Lensing And Supernova ...survey with Hubble (CLASH) multi-cycle treasury program. Our program is designed to study the dark matter distribution in 25 massive clusters, and balances depth with a wide wavelength coverage, 2000-16000 A, to better identify lensed systems and generate precise photometric redshifts. This photometric information together with the predictive strength of our strong-lensing analysis method identifies 13 new multiply lensed images and candidates, so that a total of 27 multiple images of nine systems are used to tightly constrain the inner mass profile gradient, dlog Delta *S/dlog r --0.6 ? 0.1 (r < 160 kpc). We find consistency with the standard distance-redshift relation for the full range spanned by the lensed images, 1.01 < z < 6.03, with the higher-redshift sources deflected through larger angles as expected. The inner mass profile derived here is consistent with the results of our independent weak-lensing analysis of wide-field Subaru images, with good agreement in the region of overlap (~0.7-1 arcmin). Combining weak and strong lensing, the overall mass profile is well fitted by a Navarro-Frenk-White profile with M vir = (5.37+0.70 -- 0.63 ? 0.26) X 1014 M h --1 and a relatively high concentration, c vir = 8.77+0.44 -- 0.42 ? 0.23, which lies above the standard c-M relation similar to other well-studied clusters. The critical radius of A383 is modest by the standards of other lensing clusters, rE 16 ? 2'' (for zs = 2.55), so the relatively large number of lensed images uncovered here with precise photometric redshifts validates our imaging strategy for the CLASH survey. In total we aim to provide similarly high-quality lensing data for 25 clusters, 20 of which are X-ray-selected relaxed clusters, enabling a precise determination of the representative mass profile free from lensing bias.
We derive the stellar mass fraction in the galaxy cluster RXC J2248.7-4431 observed with the Dark Energy Survey (DES) during the Science Verification period. We compare the stellar mass results from ...DES (five filters) with those from the Hubble Space Telescope Cluster Lensing And Supernova Survey (CLASH; 17 filters). When the cluster spectroscopic redshift is assumed, we show that stellar masses from DES can be estimated within 25 per cent of CLASH values. We compute the stellar mass contribution coming from red and blue galaxies, and study the relation between stellar mass and the underlying dark matter using weak lensing studies with DES and CLASH. An analysis of the radial profiles of the DES total and stellar mass yields a stellar-to-total fraction of f... = (6.8 plus or minus 1.7) x 10 super( -3) within a radius of r sub( 200c) ... 2 Mpc. Our analysis also includes a comparison of photometric redshifts and star/galaxy separation efficiency for both data sets. We conclude that space-based small field imaging can be used to calibrate the galaxy properties in DES for the much wider field of view. The technique developed to derive the stellar mass fraction in galaxy clusters can be applied to the ~100 000 clusters that will be observed within this survey and yield important information about galaxy evolution. (ProQuest: ... denotes formulae/symbols omitted.)
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