1,355 research outputs found

    The Tolman Surface Brightness Test for the Reality of the Expansion. III. HST Profile and Surface Brightness Data for Early-Type Galaxies in Three High-Redshift Clusters

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    Photometric data for 34 early-type galaxies in the three high-redshift clusters Cl 1324+3011 (z = 0.76), Cl 1604+4304 (z = 0.90), and Cl 1604+4321 (z = 0.92), observed with the Hubble Space Telescope (HST) and with the Keck 10-meter telescopes by Oke, Postman & Lubin, are analyzed to obtain the photometric parameters of mean surface brightness, magnitudes for the growth curves, and angular radii at various Petrosian eta radii. The angular radii at eta = 1.3 mag for the program galaxies are all larger than 0.24". All of the galaxies are well resolved at this angular size using HST whose point-spread function is 0.05", half width at half maximum. The data for each of the program galaxies are listed at eta = 1.0, 1.3, 1.5, 1.7, and 2.0 mag. They are corrected by color equations and K terms for the effects of redshift to the rest-frame Cape/Cousins I for Cl 1324+3011 and Cl 1604+4304 and R for Cl 1604+4321. The K corrections are calculated from synthetic spectral energy distributions derived from evolving stellar population models of Bruzual & Charlot which have been fitted to the observed broad-band (BVRI) AB magnitudes of each program galaxy. The listed photometric data are independent of all cosmological parameters. They are the source data for the Tolman surface brightness test made in Paper IV.Comment: 17 pages, 7 figures; accepted for publication in the Astronomical Journa

    A Statistical Treatment of the Gamma-Ray Burst "No Host Galaxy" Problem: II. Energies of Standard Candle Bursts

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    With the discovery that the afterglows after some bursts are coincident with faint galaxies, the search for host galaxies is no longer a test of whether bursts are cosmological, but rather a test of particular cosmological models. The methodology we developed to investigate the original "no host galaxy" problem is equally valid for testing different cosmological models, and is applicable to the galaxies coincident with optical transients. We apply this methodology to a family of models where we vary the total energy of standard candle bursts. We find that total isotropic energies of E<2e52~erg are ruled out while log(E)~53 erg is favored.Comment: To appear in Ap.J., 514, 15 pages + 7 figures, AASTeX 4.0. Revisions are: additional author, updated data, and minor textual change

    The Dipole Anisotropy of the First All-Sky X-ray Cluster Sample

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    We combine the recently published CIZA galaxy cluster catalogue with the XBACs cluster sample to produce the first all-sky catalogue of X-ray clusters in order to examine the origins of the Local Group's peculiar velocity without the use of reconstruction methods to fill the traditional Zone of Avoidance. The advantages of this approach are (i) X-ray emitting clusters tend to trace the deepest potential wells and therefore have the greatest effect on the dynamics of the Local Group and (ii) our all-sky sample provides data for nearly a quarter of the sky that is largely incomplete in optical cluster catalogues. We find that the direction of the Local Group's peculiar velocity is well aligned with the CMB as early as the Great Attractor region 40 h^-1 Mpc away, but that the amplitude of its dipole motion is largely set between 140 and 160 h^-1 Mpc. Unlike previous studies using galaxy samples, we find that without Virgo included, roughly ~70% of our dipole signal comes from mass concentrations at large distances (>60 h^-1 Mpc) and does not flatten, indicating isotropy in the cluster distribution, until at least 160 h^-1 Mpc. We also present a detailed discussion of our dipole profile, linking observed features to the structures and superclusters that produce them. We find that most of the dipole signal can be attributed to the Shapley supercluster centered at about 150 h^-1 Mpc and a handful of very massive individual clusters, some of which are newly discovered and lie well in the Zone of Avoidance.Comment: 15 Pages, 9 Figures. Accepted by Ap

    System Tests of the ATLAS Pixel Detector

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    The innermost part of the ATLAS (A Toroidal LHC ApparatuS) experiment at the LHC (Large Hadron Collider) will be a pixel detector, which is presently under construction. Once installed into the experimental area, access will be extremely limited. To ensure that the integrated detector assembly operates as expected, a fraction of the detector which includes the power supplies and monitoring system, the optical readout, and the pixel modules themselves, has been assembled and operated in a laboratory setting for what we refer to as system tests. Results from these tests are presented.Comment: 5 Pages, 9 Figures, to appear in Proceedings of the Eleventh Workshop on Electronics for LHC and Future Experiment

    A Serendipitous Galaxy Cluster Survey with XMM: Expected Catalogue Properties and Scientific Applications

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    This paper describes a serendipitous galaxy cluster survey that we plan to conduct with the XMM X-ray satellite. We have modeled the expected properties of such a survey for three different cosmological models, using an extended Press-Schechter (Press & Schechter 1974) formalism, combined with a detailed characterization of the expected capabilities of the EPIC camera on board XMM. We estimate that, over the ten year design lifetime of XMM, the EPIC camera will image a total of ~800 square degrees in fields suitable for the serendipitous detection of clusters of galaxies. For the presently-favored low-density model with a cosmological constant, our simulations predict that this survey area would yield a catalogue of more than 8000 clusters, ranging from poor to very rich systems, with around 750 detections above z=1. A low-density open Universe yields similar numbers, though with a different redshift distribution, while a critical-density Universe gives considerably fewer clusters. This dependence of catalogue properties on cosmology means that the proposed survey will place strong constraints on the values of Omega-Matter and Omega-Lambda. The survey would also facilitate a variety of follow-up projects, including the quantification of evolution in the cluster X-ray luminosity-temperature relation, the study of high-redshift galaxies via gravitational lensing, follow-up observations of the Sunyaev-Zel'dovich effect and foreground analyses of cosmic microwave background maps.Comment: Accepted to ApJ. Minor changes, e.g. presentation of temperature errors as a figure (rather than as a table). Latex (20 pages, 6 figures, uses emulateapj.sty

    Large-scale periodicity in the distribution of QSO absorption-line systems

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    The spatial-temporal distribution of absorption-line systems (ALSs) observed in QSO spectra within the cosmological redshift interval z = 0.0--4.3 is investigated on the base of our updated catalog of absorption systems. We consider so called metallic systems including basically lines of heavy elements. The sample of the data displays regular variations (with amplitudes ~ 15 -- 20%) in the z-distribution of ALSs as well as in the eta-distribution, where eta is a dimensionless line-of-sight comoving distance, relatively to smoother dependences. The eta-distribution reveals the periodicity with period Delta eta = 0.036 +/- 0.002, which corresponds to a spatial characteristic scale (108 +/- 6) h(-1) Mpc or (alternatively) a temporal interval (350 +/- 20) h(-1) Myr for the LambdaCDM cosmological model. We discuss a possibility of a spatial interpretation of the results treating the pattern obtained as a trace of an order imprinted on the galaxy clustering in the early Universe.Comment: AASTeX, 13 pages, with 9 figures, Accepted for publication in Astrophysics & Space Scienc

    Optical and X-ray clusters as tracers of the supercluster-void network. I Superclusters of Abell and X-ray clusters

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    We study the distribution of X-ray selected clusters of galaxies with respect to superclusters determined by Abell clusters of galaxies and show that the distribution of X-ray clusters follows the supercluster-void network determined by Abell clusters. We find that in this network X-ray clusters are more strongly clustered than other clusters. Poor, non-Abell X-ray clusters follow the supercluster-void network as well: these clusters are embedded in superclusters determined by rich clusters and populate filaments between them. We present a new catalog of superclusters of Abell clusters out to a redshift of z_{lim}=0.13, a catalog of X-ray clusters located in superclusters determined by Abell clusters, and a list of additional superclusters of X-ray clusters.Comment: LaTex (sty files added), 16 pages, 3 ps figures, submitted to Astronomical Journal. Animations of the 3D distribution of superclusters of Abell and X-ray clusters at http://www.aai.ee/~maret/SCLVnet.ht

    Colour reconnection in e+e- -> W+W- at sqrt(s) = 189 - 209 GeV

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    The effects of the final state interaction phenomenon known as colour reconnection are investigated at centre-of-mass energies in the range sqrt(s) ~ 189-209 GeV using the OPAL detector at LEP. Colour reconnection is expected to affect observables based on charged particles in hadronic decays of W+W-. Measurements of inclusive charged particle multiplicities, and of their angular distribution with respect to the four jet axes of the events, are used to test models of colour reconnection. The data are found to exclude extreme scenarios of the Sjostrand-Khoze Type I (SK-I) model and are compatible with other models, both with and without colour reconnection effects. In the context of the SK-I model, the best agreement with data is obtained for a reconnection probability of 37%. Assuming no colour reconnection, the charged particle multiplicity in hadronically decaying W bosons is measured to be (nqqch) = 19.38+-0.05(stat.)+-0.08 (syst.).Comment: 30 pages, 9 figures, Submitted to Euro. Phys. J.

    Search for R-Parity Violating Decays of Scalar Fermions at LEP

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    A search for pair-produced scalar fermions under the assumption that R-parity is not conserved has been performed using data collected with the OPAL detector at LEP. The data samples analysed correspond to an integrated luminosity of about 610 pb-1 collected at centre-of-mass energies of sqrt(s) 189-209 GeV. An important consequence of R-parity violation is that the lightest supersymmetric particle is expected to be unstable. Searches of R-parity violating decays of charged sleptons, sneutrinos and squarks have been performed under the assumptions that the lightest supersymmetric particle decays promptly and that only one of the R-parity violating couplings is dominant for each of the decay modes considered. Such processes would yield final states consisting of leptons, jets, or both with or without missing energy. No significant single-like excess of events has been observed with respect to the Standard Model expectations. Limits on the production cross- section of scalar fermions in R-parity violating scenarios are obtained. Constraints on the supersymmetric particle masses are also presented in an R-parity violating framework analogous to the Constrained Minimal Supersymmetric Standard Model.Comment: 51 pages, 24 figures, Submitted to Eur. Phys. J.

    Bose-Einstein Correlations in e+e- to W+W- at 172 and 183 GeV

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    Bose-Einstein correlations between like-charge pions are studied in hadronic final states produced by e+e- annihilations at center-of-mass energies of 172 and 183 GeV. Three event samples are studied, each dominated by one of the processes W+W- to qqlnu, W+W- to qqqq, or (Z/g)* to qq. After demonstrating the existence of Bose-Einstein correlations in W decays, an attempt is made to determine Bose-Einstein correlations for pions originating from the same W boson and from different W bosons, as well as for pions from (Z/g)* to qq events. The following results are obtained for the individual chaoticity parameters lambda assuming a common source radius R: lambda_same = 0.63 +- 0.19 +- 0.14, lambda_diff = 0.22 +- 0.53 +- 0.14, lambda_Z = 0.47 +- 0.11 +- 0.08, R = 0.92 +- 0.09 +- 0.09. In each case, the first error is statistical and the second is systematic. At the current level of statistical precision it is not established whether Bose-Einstein correlations, between pions from different W bosons exist or not.Comment: 24 pages, LaTeX, including 6 eps figures, submitted to European Physical Journal
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