112 research outputs found
Cosmic microwave background anisotropy power spectrum statistics for high precision cosmology
As the era of high precision cosmology approaches, the empirically determined
power spectrum of the microwave background anisotropy, , will provide a
crucial test for cosmological theories. We present a unified semi-analytic
framework for the study of the statistical properties of the coefficients
computed from the results of balloon, ground based, and satellite experiments.
An illustrative application shows that commonly used approximations {\it bias}
the estimation of the baryon parameter at the 1% level even for a
satellite capturing as much as % of the sky.Comment: 4 pages, 3 figures. Also available at
http://www.tac.dk/~wandelt/downloads.htm
Improved limits on the tensor-to-scalar ratio using BICEP and Planck data
We present constraints on the tensor-to-scalar ratio r using a combination of BICEP/Keck 2018 (BK18) and Planck PR4 data allowing us to fit for r consistently with the six parameters of the ? CDM model. We discuss the sensitivity of constraints on r to uncertainties in the ? CDM parameters as defined by the Planck data. In particular, we are able to derive a constraint on the reionization optical depth ? and thus propagate its uncertainty into the posterior distribution for r . While Planck sensitivity to r is slightly lower than the current ground-based measurements, the combination of Planck with BK18 and baryon-acoustic-oscillation data yields results consistent with r = 0 and tightens the constraint to r < 0.032 at 95% confidence.Planck is a project of the European Space Agency (ESA) with instruments provided by two scientific consortia funded by ESA member states and led by Principal Investigators from France and Italy, telescope reflectors provided through a collaboration between ESA and a scientific consortium led and funded by Denmark, and additional contributions from NASA (USA). We gratefully acknowledge support from the CNRS/IN2P3 Computing Center for providing computing and data-processing resources needed for this work. This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02- 05CH11231. Part of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (Grant No. 80NM0018D0004)
Can induced gravity isotropize Bianchi I, V, or IX Universes?
We analyze if Bianchi I, V, and IX models in the Induced Gravity (IG) theory
can evolve to a Friedmann--Roberson--Walker (FRW) expansion due to the
non--minimal coupling of gravity and the scalar field. The analytical results
that we found for the Brans-Dicke (BD) theory are now applied to the IG theory
which has ( being the square ratio of the Higgs to
Planck mass) in a cosmological era in which the IG--potential is not
significant. We find that the isotropization mechanism crucially depends on the
value of . Its smallness also permits inflationary solutions. For the
Bianch V model inflation due to the Higgs potential takes place afterwads, and
subsequently the spontaneous symmetry breaking (SSB) ends with an effective FRW
evolution. The ordinary tests of successful cosmology are well satisfied.Comment: 24 pages, 5 figures, to be published in Phys. Rev. D1
Planck intermediate results. VIII. Filaments between interacting clusters
About half of the baryons of the Universe are expected to be in the form of
filaments of hot and low density intergalactic medium. Most of these baryons
remain undetected even by the most advanced X-ray observatories which are
limited in sensitivity to the diffuse low density medium. The Planck satellite
has provided hundreds of detections of the hot gas in clusters of galaxies via
the thermal Sunyaev-Zel'dovich (tSZ) effect and is an ideal instrument for
studying extended low density media through the tSZ effect. In this paper we
use the Planck data to search for signatures of a fraction of these missing
baryons between pairs of galaxy clusters. Cluster pairs are good candidates for
searching for the hotter and denser phase of the intergalactic medium (which is
more easily observed through the SZ effect). Using an X-ray catalogue of
clusters and the Planck data, we select physical pairs of clusters as
candidates. Using the Planck data we construct a local map of the tSZ effect
centered on each pair of galaxy clusters. ROSAT data is used to construct X-ray
maps of these pairs. After having modelled and subtracted the tSZ effect and
X-ray emission for each cluster in the pair we study the residuals on both the
SZ and X-ray maps. For the merging cluster pair A399-A401 we observe a
significant tSZ effect signal in the intercluster region beyond the virial
radii of the clusters. A joint X-ray SZ analysis allows us to constrain the
temperature and density of this intercluster medium. We obtain a temperature of
kT = 7.1 +- 0.9, keV (consistent with previous estimates) and a baryon density
of (3.7 +- 0.2)x10^-4, cm^-3. The Planck satellite mission has provided the
first SZ detection of the hot and diffuse intercluster gas.Comment: Accepted by A&
Planck 2015 results. XXVII. The Second Planck Catalogue of Sunyaev-Zeldovich Sources
We present the all-sky Planck catalogue of Sunyaev-Zeldovich (SZ) sources detected from the 29 month full-mission data. The catalogue (PSZ2) is the largest SZ-selected sample of galaxy clusters yet produced and the deepest all-sky catalogue of galaxy clusters. It contains 1653 detections, of which 1203 are confirmed clusters with identified counterparts in external data-sets, and is the first SZ-selected cluster survey containing > confirmed clusters. We present a detailed analysis of the survey selection function in terms of its completeness and statistical reliability, placing a lower limit of 83% on the purity. Using simulations, we find that the Y5R500 estimates are robust to pressure-profile variation and beam systematics, but accurate conversion to Y500 requires. the use of prior information on the cluster extent. We describe the multi-wavelength search for counterparts in ancillary data, which makes use of radio, microwave, infra-red, optical and X-ray data-sets, and which places emphasis on the robustness of the counterpart match. We discuss the physical properties of the new sample and identify a population of low-redshift X-ray under- luminous clusters revealed by SZ selection. These objects appear in optical and SZ surveys with consistent properties for their mass, but are almost absent from ROSAT X-ray selected samples
Planck early results III : First assessment of the Low Frequency Instrument in-flight performance
Peer reviewe
Planck early results XVIII : The power spectrum of cosmic infrared background anisotropies
Peer reviewe
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