Download or read book Mass Calibration of Galaxy Clusters at Redshift 0 1 1 0 Using Weak Lensing in the Sloan Digital Sky Survey Stripe 82 Co add written by and published by . This book was released on 2015 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mass Calibration of Galaxy Clusters at Redshift 0 1 u2013 1 0 Using Weak Lensing in the Sloan Digital Sky Survey Stripe 82 Co add written by and published by . This book was released on 2015 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present galaxy cluster mass–richness relations found in the Sloan Digital Sky Survey Stripe 82 co-add using clusters found using a Voronoi tessellation cluster finder. These relations were found using stacked weak lensing shear observed in a large sample of galaxy clusters. These mass–richness relations are presented for four redshift bins, 0.1 z ≤ 0.4, 0.4 z ≤ 0.7, 0.7 z ≤ 1.0 and 0.1 z ≤ 1.0. We describe the sample of galaxy clusters and explain how these clusters were found using a Voronoi tessellation cluster finder. We fit a Navarro-Frenk-White profile to the stacked weak lensing shear signal in redshift and richness bins in order to measure virial mass (Msub200

Download or read book Cluster Mass Calibration at High Redshift written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present an HST/ACS weak gravitational lensing analysis of 13 massive high-redshift (z_median=0.88) galaxy clusters discovered in the South Pole Telescope (SPT) Sunyaev-Zel'dovich Survey. This study is part of a larger campaign that aims to robustly calibrate mass-observable scaling relations over a wide range in redshift to enable improved cosmological constraints from the SPT cluster sample. We introduce new strategies to ensure that systematics in the lensing analysis do not degrade constraints on cluster scaling relations significantly. First, we efficiently remove cluster members from the source sample by selecting very blue galaxies in V-I colour. Our estimate of the source redshift distribution is based on CANDELS data, where we carefully mimic the source selection criteria of the cluster fields. We apply a statistical correction for systematic photometric redshift errors as derived from Hubble Ultra Deep Field data and verified through spatial cross-correlations. We account for the impact of lensing magnification on the source redshift distribution, finding that this is particularly relevant for shallower surveys. Finally, we account for biases in the mass modelling caused by miscentring and uncertainties in the mass-concentration relation using simulations. In combination with temperature estimates from Chandra we constrain the normalisation of the mass-temperature scaling relation ln(E(z) M_500c/10^14 M_sun)=A+1.5 ln(kT/7.2keV) to A=1.81^{+0.24}_{-0.14}(stat.) +/- 0.09(sys.), consistent with self-similar redshift evolution when compared to lower redshift samples. Additionally, the lensing data constrain the average concentration of the clusters to c_200c=5.6^{+3.7}_{-1.8}.

Download or read book Weak lensing Mass Calibration of RedMaPPer Galaxy Clusters in Dark Energy Survey Science Verification Data written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We use weak-lensing shear measurements to determine the mean mass of optically selected galaxy clusters in Dark Energy Survey Science Verification data. In a blinded analysis, we split the sample of more than 8,000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter $5 \leq \lambda \leq 180$ and redshift $0.2 \leq z \leq 0.8$, and fit the averaged mass density contrast profiles with a model that accounts for seven distinct sources of systematic uncertainty: shear measurement and photometric redshift errors; cluster-member contamination; miscentering; deviations from the NFW halo profile; halo triaxiality; and line-of-sight projections. We combine the inferred cluster masses to estimate the joint scaling relation between mass, richness and redshift, $\mathcal{M}(\lambda, z) \varpropto M_0 \lambda^{F} (1+z)^{G}$. We find $M_0 \equiv \langle M_{200\mathrm{m}}\,

Download or read book Galaxy Cluster Center Detection Methods with Weak Lensing written by Melanie Simet and published by . This book was released on 2012 with total page 71 pages. Available in PDF, EPUB and Kindle. Book excerpt: The precise location of galaxy cluster centers is a persistent problem in weak lensing mass estimates and in interpretations of clusters in a cosmological context. In this work, we test methods of centroid determination from weak lensing data and examine the effects of such self-calibration on the measured masses. Drawing on lensing data from the Sloan Digital Sky Survey Stripe 82, a 275 square degree region of coadded data in the Southern Galactic Cap, together with a catalog of MaxBCG clusters, we show that halo substructure as well as shape noise and stochasticity in galaxy positions limit the precision of such a self-calibration (in the context of Stripe 82, to ∼ 500 h−1 kpc or larger) and bias the mass estimates around these points to a level that is likely unacceptable for the purposes of making cosmological measurements. We also project the usefulness of this technique in future surveys.

Download or read book Cross correlation Weak Lensing of SDSS Galaxy Clusters I written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first in a series of papers on the weak lensing effect caused by clusters of galaxies in Sloan Digital Sky Survey. The photometrically selected cluster sample, known as MaxBCG, includes (almost equal to)130,000 objects between redshift 0.1 and 0.3, ranging in size from small groups to massive clusters. We split the clusters into bins of richness and luminosity and stack the surface density contrast to produce mean radial profiles. The mean profiles are detected over a range of scales, from the inner halo (25 kpc/h) well into the surrounding large scale structure (30 Mpc/h), with a significance of 15 to 20 in each bin. The signal over this large range of scales is best interpreted in terms of the cluster-mass cross-correlation function. We pay careful attention to sources of systematic error, correcting for them where possible and bounding them where not. We find that the profiles scale strongly with richness and luminosity. We find the signal within a given richness bin depends upon luminosity, suggesting that luminosity is more closely correlated with mass than galaxy counts. We split the samples by redshift but detect no significant evolution. The profiles are not well described by power laws. In a subsequent series of papers we invert the profiles to three-dimensional mass profiles, show that they are well fit by a halo model description, measure mass-to-light ratios and provide a cosmological interpretation.

Download or read book Outskirts of Galaxies written by Johan H. Knapen and published by Springer. This book was released on 2017-07-09 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book consists of invited reviews written by world-renowned experts on the subject of the outskirts of galaxies, an upcoming field which has been understudied so far. These regions are faint and hard to observe, yet hide a tremendous amount of information on the origin and early evolution of galaxies. They thus allow astronomers to address some of the most topical problems, such as gaseous and satellite accretion, radial migration, and merging. The book is published in conjunction with the celebration of the end of the four-year DAGAL project, an EU-funded initial training network, and with a major international conference on the topic held in March 2016 in Toledo. It thus reflects not only the views of the experts, but also the scientific discussions and progress achieved during the project and the meeting. The reviews in the book describe the most modern observations of the outer regions of our own Galaxy, and of galaxies in the local and high-redshift Universe. They tackle disks, haloes, streams, and accretion as observed through deep imaging and spectroscopy, and guide the reader through the various formation and evolution scenarios for galaxies. The reviews focus on the major open questions in the field, and explore how they can be tackled in the future. This book provides a unique entry point into the field for graduate students and non-specialists, and serves as a reference work for researchers in this exciting new field.

Download or read book The Mass Of The Coma Cluster From Weak Lensing In The Sloan Digital Sky Survey written by and published by . This book was released on 2007 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a weak lensing analysis of the Coma Cluster using the Sloan Digital Sky Survey (SDSS) Data Release Five. Complete imaging of a (almost equal to) 200 square degree region is used to measure the tangential shear of this cluster. The shear is fit to an NFW model and we find a virial radius of r200 = 1.99{sup +0.21}{sub -0.22}h−1Mpc which corresponds to a virial mass of M200 = 1.88{sup +0.65}{sub -0.56} x 1015h−1M{circle_dot}. We additionally compare our weak lensing measurement to the virial mass derived using dynamical techniques, and find they are in agreement. This is the lowest redshift, largest angle weak lensing measurement of an individual cluster to date.

Download or read book The Sloan Digital Sky Survey Stripe 82 Imaging Data written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present and release co-added images of the Sloan Digital Sky Survey (SDSS) Stripe 82. Stripe 82 covers an area of ~300 deg(2) on the celestial equator, and has been repeatedly scanned 70-90 times in the ugriz bands by the SDSS imaging survey. By making use of all available data in the SDSS archive, our co-added images are optimized for depth. Input single-epoch frames were properly processed and weighted based on seeing, sky transparency, and background noise before co-addition. The resultant products are co-added science images and their associated weight images that record relative weights at individual pixels. The depths of the co-adds, measured as the 5[sigma] detection limits of the aperture (3.''2 diameter) magnitudes for point sources, are roughly 23.9, 25.1, 24.6, 24.1, and 22.8 AB magnitudes in the five bands, respectively. They are 1.9-2.2 mag deeper than the best SDSS single-epoch data. The co-added images have good image quality, with an average point-spread function FWHM of ~1'' in the r, i, and z bands. We also release object catalogs that were made with SExtractor. These co-added products have many potential uses for studies of galaxies, quasars, and Galactic structure. We further present and release near-IR J-band images that cover ~90 deg(2) of Stripe 82. These images were obtained using the NEWFIRM camera on the NOAO 4 m Mayall telescope, and have a depth of about 20.0-20.5 Vega magnitudes (also 5[sigma] detection limits for point sources).

Download or read book Connecting Quarks with the Cosmos written by National Research Council and published by National Academies Press. This book was released on 2003-03-12 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances made by physicists in understanding matter, space, and time and by astronomers in understanding the universe as a whole have closely intertwined the question being asked about the universe at its two extremesâ€"the very large and the very small. This report identifies 11 key questions that have a good chance to be answered in the next decade. It urges that a new research strategy be created that brings to bear the techniques of both astronomy and sub-atomic physics in a cross-disciplinary way to address these questions. The report presents seven recommendations to facilitate the necessary research and development coordination. These recommendations identify key priorities for future scientific projects critical for realizing these scientific opportunities.

Download or read book Magnified Weak Lensing Cross Correlation Tomography written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This project carried out a weak lensing tomography (WLT) measurement around rich clusters of galaxies. This project used ground based photometric redshift data combined with HST archived cluster images that provide the WLT and cluster mass modeling. The technique has already produced interesting results (Guennou et al, 2010,Astronomy & Astrophysics Vol 523, page 21, and Clowe et al, 2011 to be submitted). Guennou et al have validated that the necessary accuracy can be achieved with photometric redshifts for our purposes. Clowe et al titled "The DAFT/FADA survey. II. Tomographic weak lensing signal from 10 high redshift clusters," have shown that for the **first time** via this purely geometrical technique, which does not assume a standard rod or candle, that a cosmological constant is **required** for flat cosmologies. The intent of this project is not to produce the best constraint on the value of the dark energy equation of state, w. Rather, this project is to carry out a sustained effort of weak lensing tomography that will naturally feed into the near term Dark Energy Survey (DES) and to provide invaluable mass calibration for that project. These results will greatly advance a key cosmological method which will be applied to the top-rated ground-based project in the Astro2020 decadal survey, LSST. Weak lensing tomography is one of the key science drivers behind LSST. CO-I Clowe is on the weak lensing LSST committee, and senior scientist on this project, at FNAL James Annis, plays a leading role in the DES. This project has built on successful proposals to obtain ground-based imaging for the cluster sample. By 1 Jan, it is anticipated the project will have accumulated complete 5-color photometry on 30 (or about 1/3) of the targeted cluster sample (public webpage for the survey is available at http://cencos.oamp.fr/DAFT/ and has a current summary of the observational status of various clusters). In all, the project has now been awarded the equivalent of over 60 nights on 4-m class telescopes, which gives concrete evidence of strong community support for this project. The WLT technique is based on the dependence of the gravitational shear signal on the angular diameter distances between the observer, the lens, and the lensed galaxy to measure cosmological parameters. By taking the ratio of measured shears of galaxies with different redshifts around the same lens, one obtains a measurement of the ratios of the angular diameter distances involved. Making these observations over a large range of lenses and background galaxy redshifts will measure the history of the expansion rate of the universe. Because this is a purely geometric measurement, it is insensitive to any form of evolution of objects or the necessity to understand the physics in the early universe. Thus, WLT was identified by the Dark Energy Task Force as perhaps the best method to measure the evolution of DE. To date, however, the conjecture of the DETF has not been experimentally verified, but will be by the proposed project. The primary reason for the lack of tomography measurements is that one must have an exceptional data-set to attempt the measurement. One needs both extremely good seeing (or space observations) in order to minimize the point spread function smearing corrections on weak lensing shear measurements and deep, multi-color data, from B to z, to measure reliable photometric redshifts of the background galaxies being lensed (which are typically too faint to obtain spectroscopic redshifts). Because the entire process from multi-drizzling the HST images, and then creating shear maps, to gathering the necessary ground based observations, to generating photo-zs and then carrying out the tomography is a complicated task, until the creation of our team, nobody has taken the time to connect all the levels of expertise necessary to carry out this project based on HST archival data. Our data are being used in 2 Ph.D. theses. Kellen Murphy, at Ohio Universi ...

Download or read book Cross correlation Weak Lensing of SDSS Galaxy Clusters III written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present measurements of the excess mass-to-light ratio measured around MaxBCG galaxy clusters observed in the SDSS. This red sequence cluster sample includes objects from small groups with M200 H"5 x 1012h−1M{sub {circle_dot}} to clusters with M200 H"5 x 1015h−1M{sub {circle_dot}}. Using cross-correlation weak lensing, we measure the excess mass density profile above the universal mean [Delta]2!r) = [rho](r) -- {bar [rho]} for clusters in bins of richness and optical luminosity. We also measure the excess {sup 0.25}i-band luminosity density [Delta]l(r) = l(r) -- {bar {ell}}. For both mass and light, we de-project the profiles to produce 3D mass and light profiles over scales from 25h−1 kpc to 22h−1 Mpc. From these profiles we calculate the cumulative excess mass [Delta]M(r) and excess light [Delta]L(r) as a function of separation from the BCG. On small scales, where [rho](r)” {bar {rho}}, the integrated mass-to-light profile ([Delta]M/[Delta]L)(r) may be interpreted as the cluster mass-to-light ratio. We find the ([Delta]M/[Delta]L)200, the mass-to-light ratio within r200, scales with cluster mass as a power law with index 0.33±0.02. On large scales, where {rho}(r) H"{bar {rho}}, the [Delta]M/[Delta]L approaches an asymptotic value independent of scale or cluster richness. For small groups, the mean ([Delta]M/[Delta]L)200 is much smaller than the asymptotic value, while for large clusters ([Delta]M/[Delta]L)200 is consistent with the asymptotic value. This asymptotic value should be proportional to the mean mass-to-light ratio of the universe {l_angle}M/L{r_angle}. We find {l_angle}M/L{r_angle} b−2{sub M/L} = 362 ± 54h measured in the {sup 0.25}i-bandpass. The parameter b2{sub M/L} is primarily a function of the bias of the L H" L* galaxies used as light tracers, and should be of order unity. Multiplying by the luminosity density in the same bandpass we find [Omega]{sub m}b−2{sub M/L}= 0.20 ± 0.03, independent of the Hubble parameter.

Download or read book High redshift Universe written by Gregory Zeimann and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the discovery of only the second radio-selected, z ~ 6 quasar. We identified the z=5.95 quasar by matching the optical detections of the deep Sloan Digital Sky Survey (SDSS) Stripe 82 with their radio counterparts in the Stripe82 VLA Survey. The discovered quasar is optically-faint, z = 22.3 and M1450 ~ -24.5, but radio-bright, with a flux density of f[subscript 1.4GHz, peak] = 0.31mJy and a radio-loudness of R ~ 1100 (where R = f[subscript 5GHz]/f2500). The i - z color of the discovered quasar places it outside the color selection criteria for existing optical surveys. We also report the discovery of an IR-selected galaxy cluster in the IRAC Distant Cluster Survey (IDCS). New data from the Hubble Space Telescope spectroscopically confirm the galaxy cluster at z = 1.89 with robust spectroscopic redshifts for seven members. The cluster exhibits a red sequence with a scatter and color indicative of a formation redshift z[subscript f]>~ 3.5. The stellar age of the early-type galaxy population is approximately consistent with those of clusters at lower redshift (1 z 1.5) suggesting that clusters at these redshifts are experiencing ongoing or increasing star formation. Finally, we present near-IR spectroscopy for 18 galaxy clusters at 1.0

Download or read book Improving Accuracy in Gravitational Weak Lensing Measurements of Clusters written by Julia Young and published by . This book was released on 2013 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Measuring the distribution of galaxy clusters provides a powerful constraint on cosmological parameters. Currently, the largest challenge for using the observed abundance of clusters to constrain cosmology is to measure their mass accurately. The best tool to measure the mass of clusters is weak gravitational lensing, which measures the baryonic and dark matter present in galaxy clusters by observing the distortion of the shape of sources behind the gravitational lens called shear. Weak lensing measurements are technically challenging to measure due to the distortion in the shape of sources from the atmosphere and telescope optics called the Point Spread Function or PSF. To measure shear, images are processed by various software programs called lensing pipelines which correct for the distortion due to the PSF. Using image simulations with sources of known characteristics and known shear the systematic error of different lensing pipelines can be compared. In this dissertation the results of the Cluster Shear TEsting Program (CSTEP), a test of lensing pipelines on simulated images, is presented. CSTEP was developed to accurately measure the systematic bias on weak lensing measurements of clusters expected by the Dark Energy Survey (DES). The systematic error from lensing pipelines is then used to predict the error on mass measurements of galaxy clusters observed by DES.

Download or read book Self calibration of Photometric Redshift Scatter in Weak lensing Surveys written by and published by . This book was released on 2010 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photo-z errors, especially catastrophic errors, are a major uncertainty for precision weak lensing cosmology. We find that the shear-(galaxy number) density and density-density cross correlation measurements between photo-z bins, available from the same lensing surveys, contain valuable information for self-calibration of the scattering probabilities between the true-z and photo-z bins. The self-calibration technique we propose does not rely on cosmological priors nor parameterization of the photo-z probability distribution function, and preserves all of the cosmological information available from shear-shear measurement. We estimate the calibration accuracy through the Fisher matrix formalism. We find that, for advanced lensing surveys such as the planned stage IV surveys, the rate of photo-z outliers can be determined with statistical uncertainties of 0.01-1% for z

Download or read book Clustering of High Redshift z 2 9 Quasars from the Sloan Digital Sky Survey written by and published by . This book was released on 2006 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: We study the two-point correlation function of a uniformly selected sample of 4,428 optically selected luminous quasars with redshift 2.9 ≤ z ≤ 5.4 selected over 4041 deg2 from the Fifth Data Release of the Sloan Digital Sky Survey. We fit a power-law to the projected correlation function w{sub p}(r{sub p}) to marginalize over redshift space distortions and redshift errors. For a real-space correlation function of the form [zeta](r) = (r/r0){sup -[gamma]}, the fitted parameters in comoving coordinates are r0 = 15.2 ± 2.7 h−1 Mpc and [gamma] = 2.0 ± 0.3, over a scale range 4 ≤ r{sub p} ≤ 150 h−1 Mpc. Thus high-redshift quasars are appreciably more strongly clustered than their z ≈ 1.5 counterparts, which have a comoving clustering length r0 ≈ 6.5 h−1 Mpc. Dividing our sample into two redshift bins: 2.9 ≤ z ≤ 3.5 and z ≥ 3.5, and assuming a power-law index {gamma} = 2.0, we find a correlation length of r0 = 16.9 ± 1.7 h−1 Mpc for the former, and r0 = 24.3 ± 2.4 h−1 Mpc for the latter. Strong clustering at high redshift indicates that quasars are found in very massive, and therefore highly biased, halos. Following Martini & Weinberg, we relate the clustering strength and quasar number density to the quasar lifetimes and duty cycle. Using the Sheth & Tormen halo mass function, the quasar lifetime is estimated to lie in the range 4 ≈ 50 Myr for quasars with 2.9 ≤ z ≤ 3.5; and 30 ≈ 600 Myr for quasars with z ≥ 3.5. The corresponding duty cycles are 0.004 ≈ 0.05 for the lower redshift bin and 0.03 ≈ 0.6 for the higher redshift bin. The minimum mass of halos in which these quasars reside is 2-3 x 1012 h−1 M{sub {circle_dot}} for quasars with 2.9 ≤ z ≤ 3.5 and 4-6 x 1012 h−1 M{sub {circle_dot}} for quasars with z ≥ 3.5; the effective bias factor b{sub eff} increases with redshift, e.g., b{sub eff} ≈ 8 at z = 3.0 and b{sub eff} ≈ 16 at z = 4.5.

Download or read book Astronomical Data Analysis Software and Systems X written by Frank Roderic Harnden and published by . This book was released on 2001 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt: