The non-Gaussian tail of cosmic-shear statistics     

Guido Kruse  Peter Schneider 《Monthly notices of the Royal Astronomical Society》2000,318(2):321-328

Owing to gravitational instability, an initially Gaussian density field develops non-Gaussian features as the Universe evolves. The most prominent non-Gaussian features are massive haloes, visible as clusters of galaxies. The distortion of high-redshift galaxy images because of the tidal gravitational field of the large-scale matter distribution, called cosmic shear, can be used to investigate the statistical properties of the large‐scale structure (LSS) . In particular, non-Gaussian properties of the LSS will lead to a non-Gaussian distribution of cosmic-shear statistic. The aperture mass ( M _ap) statistics, recently introduced as a measure for cosmic shear, is particularly well suited for measuring these non-Gaussian properties. In this paper we calculate the highly non-Gaussian tail of the aperture mass probability distribution, assuming Press–Schechter theory for the halo abundance and the 'universal' density profile of haloes as obtained from numerical simulations. We find that for values of M _ap much larger than its dispersion, this probability distribution is closely approximated by an exponential, rather than a Gaussian. We determine the amplitude and shape of this exponential for various cosmological models and aperture sizes, and show that wide-field imaging surveys can be used to distinguish between some of the currently most popular cosmogonies. Our study here is complementary to earlier cosmic-shear investigations, which focused more on two- and three-point statistical properties.  相似文献   

Stochastic background of gravitational waves generated by a cosmological population of young, rapidly rotating neutron stars     

Valeria Ferrari  Sabino Matarrese  Raffaella Schneider 《Monthly notices of the Royal Astronomical Society》1999,303(2):258-264

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Organic geochemical evidence for environmental changes since 34,000 yrs BP from Lago di Mezzano, central Italy     

Heinz Wilkes  Antje Ramrath  Jörg F.W. Negendank 《Journal of Paleolimnology》1999,22(4):349-365

The composition of organic matter in a 34,000 yr sediment profile from Lago di Mezzano, central Italy, was investigated by bulk organic geochemical methods and analyses of lipid distributions. High relative amounts of long-chain fatty acids, n-alkanols and n-alkanes from the cuticular waxes of terrestrial plants in the Late Pleistocene sediments indicate a high relative proportion of allochthonous organic matter. In the Holocene sediments higher relative amounts of algal and bacterial lipids are detected which indicate a higher relative contribution of autochthonous organic matter. These results are corroborated by Hydrogen Index (HI) and Oxygen Index (OI) values from Rock-Eval pyrolysis which show a good general correlation with the TOC content indicating significant variations of the organic matter composition. Variations of HI and OI observed for different lithozones of the sediment profile can be related to environmental and climatic changes throughout the lake history. Both bulk organic geochemical and molecular data point to a good overall preservation of the organic matter.  相似文献   

The importance of submerged macrophytes as indicators for the nutrient concentration in a small stream (Rotbach, Bavaria)     

Angela Schorer  Susanne Schneider  Arnulf Melzer 《Limnologica》2000,30(4):351-358

The relationship between the macrophyte vegetation and the nutrient concentration of the water and the sediment of a stream was studied. The small stream is fed by calcareous groundwater. The alteration in the macrophyte vegetation of the stream Rotbach from oligotrophic community towards more eutrophic species is associated with an increasing concentration of nutrients in the sediment. Particularly the concentration of SRP-P in the interstitial water changes significantly.

In terms of the macrophyte vegetation the stream can be divided into 4 floristic zones, A-D. The zones are labelled in a sequence according to their sediment's nutrient content. The chemical analyses of the water and the sediment show the highest concentrations in zone D. It is characterized by the presence of Zannichellia palustris. The zones A-C have almost the same very low nutrient concentration in the water but show a different content of nutrients in the sediment, particularly of the SRP-P in the interstitial water. Zone A which is dominated by Chara hispida shows the lowest SRP-P in the interstitial water. Within zone B which is characterized by Mentha aquatica and Nasturtium officinale and even more in zone C where Chara hispida is less abundant and Elodea canadensis occurs, the SRP-P content is elevated.

The nutrient concentration in the sediment is clearly associated with changes in the macrophyte vegetation of the stream Rotbach.  相似文献   

Seismic and Aseismic Movements in the Western Bohemia/Vogtland Area     

Bankwitz  E.  Bankwitz  P.  Schneider  G. 《Studia Geophysica et Geodaetica》2000,44(4):611-613

Studia Geophysica et Geodaetica -  相似文献   

Boron in the Bolivian tin belt   总被引：1，自引：0，他引：1  

B. Lehmann  A. Dietrich  J. Heinhorst  N. Métrich  M. Mosbah  C. Palacios  H. -J. Schneider  A. Wallianos  J. Webster  L. Winkelmann 《Mineralium Deposita》2000,35(2-3):223-232

Tourmaline alteration and high boron contents are typical features of the magmatic-hydrothermal systems of the Bolivian tin province. The average boron content in melt inclusions of quartz phenocrysts from tin porphyry systems is 225 ppm (1σ-variation range: 110–420 ppm; n=12) and suggests a magmatic boron input to the hydrothermal tin systems, and not shallow post-magmatic leaching of boron from pelitic country rocks. Boron data from melt inclusions correlate positively with cesium, rubidium and arsenic, and negatively with lithium, titanium and zirconium, and define magmatic fractionation trends. The generally high B, As, Cs and Li contents in melt inclusions suggest involvement of pelitic source lithologies undepleted in these fluid-mobile components, i.e. first-cycle metamorphic rocks. Magmatic fractionation modified the trace-element contents within a one-log-unit range. Bulk-rock Nd isotope data (ɛ_Nd−5 to −10) are in agreement with the dominantly intracrustal geochemical signature of the Bolivian tin porphyry systems, but also imply a variable but minor mantle input. The metallogeny of the tin belt is likely a consequence of intracrustal melting of Lower Paleozoic pelitic and slightly carbonaceous source material, combined with an extended magmatic evolution. The long-lived thermal preparation of the root zones of the silicic systems is provided by mafic magma which also leaves a chemical imprint in the form of the hybrid dacitic bulk composition of the tin porphyry systems. Received: 6 August 1998 / Accepted: 19 August 1999  相似文献   

Variations of the Ashen Light of Moon and the Earth's albedo     

Heinz Hilbrecht  Gerd Küveler 《Earth, Moon, and Planets》1985,33(3):229-230

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The effect of large-scale structure on the SDSS galaxy three-point correlation function     

R. C. Nichol  R. K. Sheth  Y. Suto  A. J. Gray  I. Kayo  R. H. Wechsler †  F. Marin  G. Kulkarni  M. Blanton  A. J. Connolly  J. P. Gardner  B. Jain  C. J. Miller  A. W. Moore  A. Pope  J. Pun  D. Schneider  J. Schneider  A. Szalay  I. Szapudi  I. Zehavi  N. A. Bahcall  I. Csabai  J. Brinkmann 《Monthly notices of the Royal Astronomical Society》2006,368(4):1507-1514

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Spherically symmetric cosmological perturbations in the de Donder gauge (III)     

Mark Israelit  Bernhard Rose  Heinz Dehnen 《Astrophysics and Space Science》1994,220(1):39-48

The evolution of a perfect fluid perturbation is considered in the radiation dominated period and in the dust epoch. In the investigation we make use of the general formalism developed in previous papers.It turns out that the evolution tendency is predicted by the state of the cosmic background. The radiation dominated universe does not stimulate growing processes of the perturbation, whereas the dust dominated universe causes a growing tendency of small perfect fluid formations. The results of this work are in accordance with these obtained by the present writers in a previous work.  相似文献   

Gamma-ray bursts from the first stars: neutrino signals     

Raffaella Schneider  Dafne Guetta  rea Ferrara 《Monthly notices of the Royal Astronomical Society》2002,334(1):173-181

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