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
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
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
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
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
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
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
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
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
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
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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