[Show abstract][Hide abstract] ABSTRACT: Extreme value statistics (EVS) is applied to the distribution of galaxy
luminosities in the Sloan Digital Sky Survey (SDSS). We analyze the DR8 Main
Galaxy Sample (MGS), as well as the Luminous Red Galaxies (LRG). Maximal
luminosities are sampled from batches consisting of elongated pencil beams in
the radial direction of sight. For the MGS, results suggest a small and
positive tail index $\xi$, effectively ruling out the possibility of having a
finite maximum cutoff luminosity, and implying that the luminosity distribution
function may decay as a power law at the high luminosity end. Assuming,
however, $\xi=0$, a non-parametric comparison of the maximal luminosities with
the Fisher-Tippett-Gumbel distribution (limit distribution for variables
distributed by the Schechter fit) indicates a good agreement provided
uncertainties arising both from the finite batch size and from the batch size
distribution are accounted for. For a volume limited sample of LRGs, results
show that they can be described as being the extremes of a luminosity
distribution with an exponentially decaying tail, provided the uncertainties
related to batch-size distribution are taken care of.
Full-text · Article · Mar 2012 · The Astrophysical Journal
[Show abstract][Hide abstract] ABSTRACT: 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 (θEin > 35'' at zs = 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 (σz
~ 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).
Full-text · Article · Mar 2012 · The Astrophysical Journal Supplement Series
[Show abstract][Hide abstract] ABSTRACT: 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 ?, 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 ?/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) × 1014M
?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.
Full-text · Article · Nov 2011 · The Astrophysical Journal
[Show abstract][Hide abstract] ABSTRACT: 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 dlog Σ/dlog θ –0.55 ± 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 zs 2.5, the critical curve encloses a large area with an effective Einstein radius of θE
= 28'' ± 3'', and a projected mass of (1.34 ± 0.15) × 1014M
☉. 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 ΛCDM paradigm.
Full-text · Article · Jul 2011 · The Astrophysical Journal