We present a new algorithm, CAMIRA, to identify clusters of galaxies in wide-field imaging survey data. We base our algorithm on the stellar population synthesis model to predict colours of red ...sequence galaxies at a given redshift for an arbitrary set of bandpass filters, with additional calibration using a sample of spectroscopic galaxies to improve the accuracy of the model prediction. We run the algorithm on ∼11 960 deg2 of imaging data from the Sloan Digital Sky Survey (SDSS) Data Release 8 to construct a catalogue of 71 743 clusters in the redshift range 0.1 < z < 0.6 with richness after correcting for the incompleteness of the richness estimate greater than 20. We cross-match the cluster catalogue with external cluster catalogues to find that our photometric cluster redshift estimates are accurate with low bias and scatter, and that the corrected richness correlates well with X-ray luminosities and temperatures. We use the publicly available Canada–France–Hawaii Telescope Lensing Survey shear catalogue to calibrate the mass–richness relation from stacked weak lensing analysis. Stacked weak lensing signals are detected significantly for eight subsamples of the SDSS clusters divided by redshift and richness bins, which are then compared with model predictions including miscentring effects to constrain mean halo masses of individual bins. We find the richness correlates well with the halo mass, such that the corrected richness limit of 20 corresponds to the cluster virial mass limit of about 1 × 1014 h
−1 M⊙ for the SDSS DR8 cluster sample.
Abstract
We present a new approach for fast calculation of gravitational lensing properties, including the lens potential, deflection angles, convergence, and shear, of elliptical Navarro–Frenk–White ...(NFW) and Hernquist density profiles, by approximating them by superpositions of elliptical density profiles for which simple analytic expressions of gravitational lensing properties are available. This model achieves high fractional accuracy better than 10
−4
in the range of the radius normalized by the scale radius of 10
−4
–10
3
. These new approximations are ∼300 times faster in solving the lens equation for a point source compared with the traditional approach resorting to expensive numerical integrations, and are implemented in
glafic
software.
We present a strong lens analysis of SDSS J1004
$+$
4112, a unique quasar lens produced by a massive cluster of galaxies at
$z =$
0.68, using newly developed software for gravitational lensing. We ...find that our parametric mass model well reproduces all observations, including the positions of quasar images as well as those of multiply imaged galaxies with measured spectroscopic redshifts, time delays between quasar images, and the positions of faint central images. The predicted large total magnification of
$\mu \sim$
70 suggests that the lens system is indeed a useful site for studying the fine structure of a distant quasar and its host galaxy. The dark halo component is found to be unimodal, centered on the brightest cluster galaxy and the Chandra X-ray surface brightness profile. In addition, the orientation of the halo component is quite consistent with those of the brightest cluster galaxy and member galaxy distribution, implying that the lensing cluster is a relaxed system. The radial profile of the best-fit mass model is in good agreement with a mass profile inferred from the X-ray observation. While the inner radial slope of the dark halo component is consistent with being
$-$
1, a clear dependence of the predicted A–D time delay on the slope indicates that an additional time-delay measurement will improve constraints on the mass model.
We construct a mass model of the cluster MACS J1149.6+2223 to study the expected properties of multiple images of SN Refsdal, the first example of a gravitationally lensed supernova with resolved ...multiple images recently reported by Kelly et al. We find that the best-fitting model predicts six supernova images in total, i.e. two extra images in addition to the observed four Einstein cross supernova images S1–S4. One extra image is predicted to have appeared about 17 years ago, whereas the other extra image is predicted to appear in about one year from the appearance of S1–S4, which is a testable prediction with near-future observations. The predicted magnification factors of individual supernova images range from ∼18 for the brightest image to ∼4 for the faint extra images. Confronting these predictions with future observations should provide an unprecedented opportunity to improve our understanding of cluster mass distributions.
Based on a suite of state-of-the-art high-resolution N-body simulations, we revisit the so-called halofit model as an accurate fitting formula for the nonlinear matter power spectrum. While the ...halofit model has frequently been used as a standard cosmological tool to predict the nonlinear matter power spectrum in a universe dominated by cold dark matter, its precision has been limited by the low resolution of N-body simulations used to determine the fitting parameters, suggesting the necessity of an improved fitting formula at small scales for future cosmological studies. We run high-resolution N-body simulations for 16 cosmological models around the Wilkinson Microwave Anisotropy Probe best-fit cosmological parameters (one-, three-, five-, and seven-year results), including dark energy models with a constant equation of state. The simulation results are used to re-calibrate the fitting parameters of the halofit model so as to reproduce small-scale power spectra of the N-body simulations, while keeping the precision at large scales. The revised fitting formula provides an accurate prediction of the nonlinear matter power spectrum in a wide range of wavenumbers (k < or =, slant 30h Mpc super(-1)) at redshifts 0 < or =, slant z < or =, slant 10, with 5% precision for k < or =, slant 1 h Mpc super(-1) at 0 < or =, slant z < or =, slant 10 and 10% for 1 < or =, slant k < or =, slant 10 h Mpc super(-1) at 0 < or =, slant z < or =, slant 3. We discuss the impact of the improved halofit model on weak-lensing power spectra and correlation functions, and show that the improved model better reproduces ray-tracing simulation results.
We present UV luminosity functions of dropout galaxies at with the complete Hubble Frontier Fields data. We obtain a catalog of ∼450 dropout-galaxy candidates (350, 66, and 40 at , 8, and 9, ...respectively), with UV absolute magnitudes that reach mag, ∼2 mag deeper than the Hubble Ultra Deep Field detection limits. We carefully evaluate number densities of the dropout galaxies by Monte Carlo simulations, including all lensing effects such as magnification, distortion, and multiplication of images as well as detection completeness and contamination effects in a self-consistent manner. We find that UV luminosity functions at have steep faint-end slopes, , and likely steeper slopes, at . We also find that the evolution of UV luminosity densities shows a non-accelerated decline beyond in the case of , but an accelerated one in the case of . We examine whether our results are consistent with the Thomson scattering optical depth from the Planck satellite and the ionized hydrogen fraction QH ii at based on the standard analytic reionization model. We find that reionization scenarios exist that consistently explain all of the observational measurements with the allowed parameters of and for , where is the escape fraction, Mtrunc is the faint limit of the UV luminosity function, and is the conversion factor of the UV luminosity to the ionizing photon emission rate. The length of the reionization period is estimated to be (for ), consistent with the recent estimate from Planck.
Cadenced optical imaging surveys in the next decade will be capable of detecting time-varying galaxy-scale strong gravitational lenses in large numbers, increasing the size of the statistically ...well-defined samples of multiply imaged quasars by two orders of magnitude, and discovering the first strongly lensed supernovae. We carry out a detailed calculation of the likely yields of several planned surveys, using realistic distributions for the lens and source properties and taking magnification bias and image configuration detectability into account. We find that upcoming wide-field synoptic surveys should detect several thousand lensed quasars. In particular, the Large Synoptic Survey Telescope (LSST) should find more than some 8000 lensed quasars, some 3000 of which will have well-measured time delays. The LSST should also find some 130 lensed supernovae during the 10-yr survey duration, which is compared with ∼15 lensed supernovae predicted to be found by a deep, space-based supernova survey done by the Joint Dark Energy Mission. We compute the quad fraction in each survey, predicting it to be ∼15 per cent for the lensed quasars and ∼30 per cent for the lensed supernovae. Generating a mock catalogue of around 1500 well-observed double-image lenses, as could be derived from the LSST survey, we compute the available precision on the Hubble constant and the dark energy equation parameters for the time-delay distance experiment (assuming priors from Planck): the predicted marginalized 68 per cent confidence intervals are σ(w0) = 0.15, σ(wa) = 0.41 and σ(h) = 0.017. While this is encouraging in the sense that these uncertainties are only 50 per cent larger than those predicted for a space-based Type Ia supernova sample, we show how the dark energy figure of merit degrades with decreasing knowledge of the lens mass distribution.
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