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461.
The 2dF Galaxy Redshift Survey: the bias of galaxies and the density of the Universe 总被引:1,自引:0,他引:1
Licia Verde Alan F. Heavens Will J. Percival Sabino Matarrese Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick Peder Norberg John A. Peacock Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,335(2):432-440
462.
Roberto De Propris Warrick J. Couch Matthew Colless Gavin B. Dalton Chris Collins Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Nicholas Cross Kathryn Deeley Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick Stephen Moody Peder Norberg John A. Peacock Will Percival Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,329(1):87-101
We have carried out a study of known clusters within the 2dF Galaxy Redshift Survey (2dFGRS) observed areas and have identified 431 Abell, 173 APM and 343 EDCC clusters. Precise redshifts, velocity dispersions and new centroids have been measured for the majority of these objects, and this information is used to study the completeness of these catalogues, the level of contamination from foreground and background structures along the cluster's line of sight, the space density of the clusters as a function of redshift, and their velocity dispersion distributions. We find that the Abell and EDCC catalogues are contaminated at the level of about 10 per cent, whereas the APM catalogue suffers only 5 per cent contamination. If we use the original catalogue centroids, the level of contamination rises to approximately 15 per cent for the Abell and EDCC catalogues, showing that the presence of foreground and background groups may alter the richness of clusters in these catalogues. There is a deficiency of clusters at that may correspond to a large underdensity in the Southern hemisphere. From the cumulative distribution of velocity dispersions for these clusters, we derive a space density of clusters of This result is used to constrain models for structure formation; our data favour low-density cosmologies, subject to the usual assumptions concerning the shape and normalization of the power spectrum. 相似文献
463.
The 2dF Galaxy Redshift Survey: correlation functions, peculiar velocities and the matter density of the Universe 总被引:1,自引:0,他引:1
Ed Hawkins Steve Maddox Shaun Cole Ofer Lahav Darren S. Madgwick Peder Norberg John A. Peacock Ivan K. Baldry Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole Jackson Bryn Jones Ian Lewis Stuart Lumsden Will Percival Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2003,346(1):78-96
464.
Landslides - How debris flows erode and deposit material along their paths is difficult to determine in natural settings due to the lack of warning and the rapid pace at which they occur.... 相似文献
465.
Vivienne Wild John A. Peacock Ofer Lahav Edward Conway Steve Maddox Ivan K. Baldry Carlton M. Baugh Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole Jackson Ian Lewis Stuart Lumsden Darren Madgwick Peder Norberg Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2005,356(1):247-269
466.
Elizabeth R. Stanway † rew J. Bunker Karl Glazebrook Roberto G. Abraham James Rhoads Sangeeta Malhotra David Crampton Matthew Colless Kuenley Chiu 《Monthly notices of the Royal Astronomical Society》2007,376(2):727-738
The galaxy population at z ≈ 6 has been the subject of intense study in recent years, culminating in the Hubble Ultra Deep Field (HUDF) – the deepest imaging survey yet. A large number of high-redshift galaxy candidates have been identified within the HUDF, but until now analysis of their properties has been hampered by the difficulty of obtaining spectroscopic redshifts for these faint galaxies. Our 'Gemini Lyman-Alpha at Reionization Era' (GLARE) project has been designed to undertake spectroscopic follow-up of faint ( z ' < 28.5) i '-drop galaxies at z ≈ 6 in the HUDF. In a previous paper we presented preliminary results from the first 7.5 h of data from GLARE. In this paper we detail the complete survey. We have now obtained 36 h of spectroscopy on a single GMOS slitmask from Gemini-South, with a spectral resolution of λ/ΔλFWHM ≈ 1000 . We identify five strong Lyα emitters at z > 5.5 , and a further nine possible line emitters with detections at lower significance. We also place tight constraints on the equivalent width of Lyα emission for a further ten i '-drop galaxies and examine the equivalent width distribution of this faint spectroscopic sample of z ≈ 6 galaxies. We find that the fraction of galaxies with little or no emission is similar to that at z ≈ 3 , but that the z ≈ 6 population has a tail of sources with high rest-frame equivalent widths. Possible explanations for this effect include a tendency towards stronger line emission in faint sources, which may arise from extreme youth or low metallicity in the Lyman-break population at high redshift, or possibly a top-heavy initial mass function. 相似文献
467.
We synthesize a new fluvial terrace chronostratigraphy of the Bidente and Musone Rivers cast within a broader European framework, which forms the basis of a terrace genesis and river incision model for the northern Apennines, Italy. Our model, supported by terrace long profiles, correlation to Po foreland sediments, 15 new radiocarbon dates, and published numeric and relative stratigraphic ages, highlights how drainage basin substrate drives concurrent formation of strath terraces in the Bidente basin and fill terraces in the Musone basin. Quaternary climate change paces the formative geomorphic processes through unsteady discharges of water and sediment. In the weathering-limited setting represented by the Bidente basin, siliciclastic detritus carves broad strath surfaces during glacial climates that are preserved as terraces as the river incises during the transition to an interglacial climate. In contrast, the transport-limited and carbonate detritus dominated Musone basin sees valleys deeply buried by aggradation during glacial climates followed by river incision during the transition to an interglacial climate. Incision of these rivers over the past ~1 million years has been both unsteady and non-uniform. These and all Po-Adriatic draining rivers are proximal to a base level defined by mean sea level and have little room for increasing their longitudinal profile concavities through incision, particularly in their lower reaches despite periodic glacio-eustatic drawdowns. As a result, the observed incision is best explained by rock uplift associated with active local fault or fold growth embedded in the actively thickening and uplifting Apennine foreland. 相似文献
468.
469.
Starting with the hypothesis that cosmic rays are evenly distributed in the metagalaxy, it is shown that the flux of the electron-positron component, which is produced through --e decays, following the nuclear collisions of the cosmic ray beam with the intergalactic medium, takes <-4×1016 sec to reach steady state. The corresponding value of the flux of thepositron component and its implications regarding the homogeneous model of the metagalactic origin of cosmic rays are discussed.On leave from Tata Institute of Fundamental Research, Bombay, India. 相似文献
470.