172 research outputs found
Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
Extensive experimental data from high-energy nucleus-nucleus collisions were
recorded using the PHENIX detector at the Relativistic Heavy Ion Collider
(RHIC). The comprehensive set of measurements from the first three years of
RHIC operation includes charged particle multiplicities, transverse energy,
yield ratios and spectra of identified hadrons in a wide range of transverse
momenta (p_T), elliptic flow, two-particle correlations, non-statistical
fluctuations, and suppression of particle production at high p_T. The results
are examined with an emphasis on implications for the formation of a new state
of dense matter. We find that the state of matter created at RHIC cannot be
described in terms of ordinary color neutral hadrons.Comment: 510 authors, 127 pages text, 56 figures, 1 tables, LaTeX. Submitted
to Nuclear Physics A as a regular article; v3 has minor changes in response
to referee comments. Plain text data tables for the points plotted in figures
for this and previous PHENIX publications are (or will be) publicly available
at http://www.phenix.bnl.gov/papers.htm
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 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&
Spatial and temporal facies evolution of a Lower Jurassic carbonate platform, NW Tethyan margin (Mallorca, Spain)
The variety of depositional facies of a Lower Jurassic carbonate platform has been investigated on the island of Mallorca along a transect comprising six stratigraphic profiles. Twenty-nine facies and sub-facies have been recognized, grouped into seven facies associations, ranging in depositional environment from supratidal/terrestrial and peritidal to outer platform. Spatial and temporal (2D) facies distribution along the transect reflects the evolution of the carbonate platform with time showing different facies associations, from a broad peritidal platform (stage 1) to a muddy open platform (stage 2), and finally to a peritidal to outer carbonate platform (stage 3). Stage 1 (early Sinemurian to earliest late Sinemurian) corresponds to a nearly-flat peritidal-shallow subtidal epicontinental platform with facies belts that shifted far and fast over the whole study area. The evolution from stage 1 to stage 2 (late Sinemurian) represents a rapid flooding of the epicontinental shallow platform, with more open-marine conditions, and the onset of differential subsidence. During stage 3 (latest Sinemurian), peritidal and shallow-platform environments preferentially developed to the northeast (Llevant Mountains domain) with a rapid transition to middle-outer platform environments toward the northwest (Tramuntana Range domain). Stages 1 and 3 present facies associations typical of Bahamian-type carbonates, whereas stage 2 represents the demise of the Bahamian-type carbonate factory and proliferation of muddy substrates with suspension-feeders. The described platform evolution responded to the interplay between the initial extensional tectonic phases related to Early Jurassic Tethyan rifting, contemporaneous environmental perturbations, and progressive platform flooding related to the Late Triassic–Early Jurassic worldwide marine transgression and associated accommodation changes
Observations of metals in the intra-cluster medium
Because of their deep gravitational potential wells, clusters of galaxies
retain all the metals produced by the stellar populations of the member
galaxies. Most of these metals reside in the hot plasma which dominates the
baryon content of clusters. This makes them excellent laboratories for the
study of the nucleosynthesis and chemical enrichment history of the Universe.
Here we review the history, current possibilities and limitations of the
abundance studies, and the present observational status of X-ray measurements
of the chemical composition of the intra-cluster medium. We summarise the
latest progress in using the abundance patterns in clusters to put constraints
on theoretical models of supernovae and we show how cluster abundances provide
new insights into the star-formation history of the Universe.Comment: 28 pages, 12 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 16; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
Ação do cepa e do ácido giberélico na frutificação da videira 'niagara rosada'
Studies were carried out to establish the effects of exogenous growth regulators on Vitis (labrusca x vinifera) 'Niagara Rosada' fruiting. The investigations were done in the Jundiaí Research Station, Agronomic Institute State of São Paulo, always using disease-free vineyards of good productivity. The morphological transformations of clusters were carried out under the following aspects: weight, length and width of cluster; number of berries; weight, length average and width average of berries; length average/width average ratio of berries; number of seeds; length and diameter of secondary rachis. That characteristics were determined at the time of maturity plus the total sugars, total acid, Maturity Index and reducing sugars in samples of all treatments. The experiment were conduced in order to determine the doses that resulted in the most beneficial effects, always using applications by immersion of the inflorescence. The experiment consisted of appplications of (2-chloroethyl) phosphonic acid (CEPA) at concentrations of 50, 100, 250, 500, 1,000 and 2,000 ppm, 14 days before flowering; treatments with gibberellic acid at concentrations of 100 and 200 ppm before full bloom, 10 days after full bloom, and both before plus after full bloom. Treatment with CEPA 100 ppm plus gibberellic acid 100 ppm before full bloom and check treatment were also used. The use of CEPA before flowering at the concentrations used, did not result in good results in 'Niagara Rosada' clusters; applications of gibberellic acid did not differ significantly from the nontreated vines under the conditions studied.Estudou-se o efeito da aplicação, por imersão, do CEPA (ácido 2-cloroetil fosfônico) e do ácido giberélico, 14 dias antes do florescimento, nas características morfológicas da panícula da videira Vitis (labrus-ca x vinifera) "Niagara Rosada". Alguns tratamentos com ácido giberélico foram concluídos com nova aplicação 10 dias após o florescimento. Neste experimento verificou-se que, aplicação do CEPA na concentração de 250 ppm resultou na formação de panículas com a maioria de características indesejáveis. o tratamento misto CEPA 100 ppm + ácido giberélico 100 ppm também promoveu o aparecimento de panículas subdesenvolvidas. Aplicação de ácido giberélico na concentração de 100 ppm em pré e pós-ílorescimento, resultou médias mais elevadas, com relação ao peso da panícula, comprimento da panícula, peso das bagas e comprimento da ráquis. Ácido giberélico na concentração de 100 ppm aplicado em pós-ílorescimento, promoveu uma tendência de aumento nas médias do tratamento quanto ao comprimento médio das bagas, largura média das bagas, largura do engaço e comprimento da ráquila. Devemos considerar porém, que os resultados obtidos não apresentaram diferenças significativas com relação ao controle, quanto às características das frutificações, nas condições de estudo
Planck intermediate results: III. the relation between galaxy cluster mass and Sunyaev-Zeldovich signal
We examine the relation between the galaxy cluster mass M and Sunyaev-Zeldovich (SZ) effect signal DA2 Y500 for a sample of 19 objects for which weak lensing (WL) mass measurements obtained from Subaru Telescope data are available in the literature. Hydrostatic X-ray masses are derived from XMM-Newton archive data, and the SZ effect signal is measured from Planck all-sky survey data. We find an MWL-D A2 Y500 relation that is consistent in slope and normalisation with previous determinations using weak lensing masses; however, there is a normalisation offset with respect to previous measures based on hydrostatic X-ray mass-proxy relations. We verify that our SZ effect measurements are in excellent agreement with previous determinations from Planck data. For the present sample, the hydrostatic X-ray masses at R500 are on average ~ 20 percent larger than the corresponding weak lensing masses, which is contrary to expectations. We show that the mass discrepancy is driven by a difference in mass concentration as measured by the two methods and, for the present sample, that the mass discrepancy and difference in mass concentration are especially large for disturbed systems. The mass discrepancy is also linked to the offset in centres used by the X-ray and weak lensing analyses, which again is most important in disturbed systems. We outline several approaches that are needed to help achieve convergence in cluster mass measurement with X-ray and weak lensing observations. © ESO, 2013
Planck early results. IX. XMM-Newton follow-up for validation of Planck cluster candidates
We present the XMM-Newton follow-up for confirmation of Planck cluster candidates. Twenty-five candidates have been observed to date using
snapshot (∼10 ks) exposures, ten as part of a pilot programme to sample a low range of signal-to-noise ratios (4 < S/N < 6), and a further 15 in a
programme to observe a sample of S/N > 5 candidates. The sensitivity and spatial resolution of XMM-Newton allows unambiguous discrimination
between clusters and false candidates. The 4 false candidates have S/N ≤ 4.1. A total of 21 candidates are confirmed as extended X-ray sources.
Seventeen are single clusters, the majority of which are found to have highly irregular and disturbed morphologies (about ∼70%). The remaining
four sources are multiple systems, including the unexpected discovery of a supercluster at z = 0.45. For 20 sources we are able to derive a redshift
estimate from the X-ray Fe K line (albeit of variable quality). The new clusters span the redshift range 0.09 <∼ z <∼ 0.54, with a median redshift
of z ∼ 0.37. A first determination is made of their X-ray properties including the characteristic size, which is used to improve the estimate of
the SZ Compton parameter, Y500. The follow-up validation programme has helped to optimise the Planck candidate selection process. It has also
provided a preview of the X-ray properties of these newly-discovered clusters, allowing comparison with their SZ properties, and to the X-ray
and SZ properties of known clusters observed in the Planck survey. Our results suggest that Planck may have started to reveal a non-negligible
population of massive dynamically perturbed objects that is under-represented in X-ray surveys. However, despite their particular properties, these
new clusters appear to follow the Y500–YX relation established for X-ray selected objects, where YX is the product of the gas mass and temperature
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