Cluster Lenses

Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity. Clusters act as some of the most powerful gravitational lenses in the Universe. Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified. Lensing by clusters occurs in two regimes, each with unique observational signatures. The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple-images, and arclets. The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically. Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es) - understanding cluster mass distributions and issues pertaining to cluster formation and evolution, as well as constraining the nature of dark matter; (ii) the study of the lensed objects - probing the properties of the background lensed galaxy population - which is statistically at higher redshifts and of lower intrinsic luminosity thus enabling the probing of galaxy formation at the earliest times right up to the Dark Ages; and (iii) the study of the geometry of the Universe - as the strength of lensing depends on the ratios of angular diameter distances between the lens, source and observer, lens deflections are sensitive to the value of cosmological parameters and offer a powerful geometric tool to probe Dark Energy. In this review, we present the basics of cluster lensing and provide a current status report of the field.Comment: About 120 pages - Published in Open Access at: http://www.springerlink.com/content/j183018170485723/ . arXiv admin note: text overlap with arXiv:astro-ph/0504478 and arXiv:1003.3674 by other author

Cosmological lensing ratios with DES Y1, SPT and Planck

International audienceCorrelations between tracers of the matter density field and gravitational lensing are sensitive to the evolution of the matter power spectrum and the expansion rate across cosmic time. Appropriately defined ratios of such correlation functions, on the other hand, depend only on the angular diameter distances to the tracer objects and to the gravitational lensing source planes. Because of their simple cosmological dependence, such ratios can exploit available signal-to-noise ratio down to small angular scales, even where directly modelling the correlation functions is difficult. We present a measurement of lensing ratios using galaxy position and lensing data from the Dark Energy Survey, and CMB lensing data from the South Pole Telescope and Planck, obtaining the highest precision lensing ratio measurements to date. Relative to the concordance ΛCDM model, we find a best-fitting lensing ratio amplitude of A = 1.1 ± 0.1. We use the ratio measurements to generate cosmological constraints, focusing on the curvature parameter. We demonstrate that photometrically selected galaxies can be used to measure lensing ratios, and argue that future lensing ratio measurements with data from a combination of LSST and Stage-4 CMB experiments can be used to place interesting cosmological constraints, even after considering the systematic uncertainties associated with photometric redshift and galaxy shear estimation

Dark Energy Survey Year 1 Results:tomographic cross-correlations between DES galaxies and CMB lensing from SPT+Planck

International audienceWe measure the cross-correlation between redMaGiC galaxies selected from the Dark Energy Survey (DES) year 1 data and gravitational lensing of the cosmic microwave background (CMB) reconstructed from South Pole Telescope (SPT) and Planck data over 1289  deg2. When combining measurements across multiple galaxy redshift bins spanning the redshift range of 0.15<z<0.90, we reject the hypothesis of no correlation at 19.9σ significance. When removing small-scale data points where thermal Sunyaev-Zel’dovich signal and nonlinear galaxy bias could potentially bias our results, the detection significance is reduced to 9.9σ. We perform a joint analysis of galaxy-CMB lensing cross-correlations and galaxy clustering to constrain cosmology, finding Ωm=0.276-0.030+0.029 and S8=σ8Ωm/0.3=0.800-0.094+0.090. We also perform two alternate analyses aimed at constraining only the growth rate of cosmic structure as a function of redshift, finding consistency with predictions from the concordance ΛCDM model. The measurements presented here are part of a joint cosmological analysis that combines galaxy clustering, galaxy lensing and CMB lensing using data from DES, SPT and Planck

Henkilöstötilinpäätös osana pörssiyhtiön henkilöstöraportointia : case: Palveluyritys Oy

Opinnäytetyön aiheena on henkilöstötilinpäätös. Opinnäytetyön tavoitteena on luoda malli case-yrityksen ensimmäiselle henkilöstötilinpäätökselle, jota voidaan myöhemmin hyödyntää myös koko konsernissa. Tavoitteena on myös kartoittaa henkilöstötietojärjestelmien tuottaman informaation hyödyntämismahdollisuuksia sekä tuoda esiin ne seikat, jotka vielä kaipaavat kehittämistä henkilöstöinformaation tuottamiseksi. Opinnäytetyössä tarkastellaan myös pörssiyhtiöiltä vaadittavaa henkilöstöinformaation tuottamista, sillä case-yritys tulee mahdollisesti tulevaisuudessa listautumaan Helsingin pörssiin. Teoriaosuuden lähdeaineistossa on hyödynnetty sekä kirjallista materiaalia että internetiin pohjautuvia artikkeleita. Työn empiirinen osuus perustuu henkilöstötietojärjestelmien tuottaman informaation analysointiin. Tutkimus on luonteeltaan kvantitatiivinen, jolloin henkilöstöä tarkastellaan numeeristen tietojen avulla. Empiirisessä osuudessa henkilöstön ominaisuuksia lähestytään myös graafein ja taulukoin. Empiirisen osuuden henkilöstöä kuvaavat mittarit on valittu niiden asioiden perusteella, joiden seurannan yhtiön johto on kokenut tarpeelliseksi. Tilastot ja tunnusluvut perustuvat jo olemassa oleviin tietoihin, minkä vuoksi koko henkilöstön kattavia taulukoita ei voitu tietojen puutteellisuuden vuoksi laatia. Opinnäytetyössä tarkastellaan tilikautta 1.1.–31.12.2007, mutta osa tiedoista on tilastoitu tämän jälkeiseltä ajalta. Tietojen hyödyntäminen on perusteltua siitäkin syystä, että tutkimuksen tavoitteena on kartoittaa nykyisiä raportointimahdollisuuksia sekä luoda kehitysehdotuksia henkilöstöinformaation vaivattomampaan tuottamiseen. Tutkimuksen keskeisenä tuloksena voidaan todeta, että case-yrityksen henkilöstöinformaatiojärjestelmien pohjalta pystytään nykyistäkin kattavammin hyödyntämään henkilöstöstä saatavaa tietoa. Osa seurantajärjestelmien kehityksestä on kuitenkin vielä työn alla. Järjestelmiin perustuva informaatio on vielä vajanaista, minkä vuoksi henkilöstön tilasta ei vielä voida saada täysin luotettavaa kuvaa järjestelmien tuottaman informaation avulla.This thesis focuses on the human resource statement. The aim of the study was to create a model for an enterprise’s first human resource statement. In the future this model will be used in the entire corporation. The study was completed with two goals in mind. The first goal was to explore the opportunities of utilising a personnel information system. The second goal was to bring forward issues that still need development in producing personnel information. The personnel information requried from a public limited company was also examined in this study. Sources for the theoretical part of this study included literatury material and the Internet. The empirical part of the thesis is based on the analysis of information from a personnel information system. A quantitative method was utilised in this study. This means that information relating to the personnel is described with numerical information, graphics and tables. The representational indicators of the personnel, in the empirical section, have been chosen based on factors that the case company management has experienced as useful. Statistics and key figures have been collected from already existing information. However, due to the lack of information statistics representing the entire personnel have not been possible to compile. Although this study focuses on the accounting period January 1 – December 31, 2007, some information was still compiled after this period. The reason behind the use of statistics gathered after the accounting period lies in the aim of this study. This thesis explores the possibilities of current personnel reporting and creates development proposals for easier personnel information production. The study shows that the case company can comprehensively use the diversity of the information with the current personnel information system. However, a part of the monitoring system is still under development. Thus, the information received, based on the existing system, is incomplete. And, because the present system does not include the entire personnel of the case company, a reliable picture of the personnel situation is not possible

Detection of CMB-Cluster Lensing using Polarization Data from SPTpol

We report the first detection of gravitational lensing due to galaxy clusters using only the polarization of the cosmic microwave background (CMB). The lensing signal is obtained using a new estimator that extracts the lensing dipole signature from stacked images formed by rotating the cluster-centered Stokes QU map cutouts along the direction of the locally measured background CMB polarization gradient. Using data from the SPTpol 500 deg2 survey at the locations of roughly 18 000 clusters with richness \u3bb 6510 from the Dark Energy Survey (DES) Year-3 full galaxy cluster catalog, we detect lensing at 4.8\u3c3. The mean stacked mass of the selected sample is found to be (1.43\ub10.40) 71014M e which is in good agreement with optical weak lensing based estimates using DES data and CMB-lensing based estimates using SPTpol temperature data. This measurement is a key first step for cluster cosmology with future low-noise CMB surveys, like CMB-S4, for which CMB polarization will be the primary channel for cluster lensing measurements