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121.
Darren J. Croton Peder Norberg Enrique Gaztañaga Carlton M. Baugh 《Monthly notices of the Royal Astronomical Society》2007,379(4):1562-1570
We present measurements of the higher order clustering of red and blue galaxies as a function of scale and luminosity made from the two-degree field galaxy redshift survey (2dFGRS). We use a counts-in-cells analysis to estimate the volume-averaged correlation functions, , as a function of scale up to the order of p = 5 , and also the reduced void probability function. Hierarchical amplitudes are constructed using the estimates of the correlation functions: . We find that (i) red galaxies display stronger clustering than blue galaxies at all orders measured; (ii) red galaxies show values of S p that are strongly dependent on luminosity whereas blue galaxies show no segregation in S p within the errors; this is remarkable given the segregation in the variance; (iii) the linear relative bias shows the opposite trend to the hierarchical amplitudes, with little segregation for the red sequence and some segregation for the blue; (iv) faint red galaxies deviate significantly from the 'universal' negative binomial reduced void probabilities followed by all other galaxy populations. Our results show that the characteristic colour of a galaxy population reveals a unique signature in its spatial distribution. Such signatures will hopefully further elucidate the physics responsible for shaping the cosmological evolution of galaxies. 相似文献
122.
Spijker Jeroen Recaño Joaquín Martínez Sandra Carioli Alessandra 《Journal of Geographical Systems》2021,23(2):161-207
Journal of Geographical Systems - Colombia is undergoing major changes in mortality patterns. National- and department-level cause-specific analyses have previously been carried out, but very... 相似文献
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125.
J. A. Combi J. F. Albacete Colombo L. Pellizza J. López-Santiago G. E. Romero J. Martí A. J. Muñoz-Arjonilla E. Sánchez-Ayaso P. L. Luque-Escamilla J. R. Sánchez-Sutil 《Astrophysics and Space Science》2011,331(1):53-61
We present a catalog of cross-correlated radio, infrared and X-ray sources using a very restrictive selection criteria with
an IDL-based code developed by us. The significance of the observed coincidences was evaluated through Monte Carlo simulations
of synthetic sources following a well-tested protocol. We found 3320 coincident radio/X-ray sources with a high statistical
significance characterized by the sum of error-weighted coordinate differences. For 997 of them, 2MASS counterparts were found.
The percentage of chance coincidences is less than 1%. X-ray hardness ratios of well-known populations of objects were used
to provide a crude representation of their X-ray spectrum and to make a preliminary diagnosis of the possible nature of unidentified
X-ray sources. The results support the fact that the X-ray sky is largely dominated by Active Galactic Nuclei at high galactic
latitudes (|b|≥10°). At low galactic latitudes (|b|≤10°) most of unidentified X-ray sources (∼94%) lie at |b|≤2°. This result suggests that most of the unidentified sources found toward the Milky Way plane are galactic objects. Well-known
and unidentified sources were classified in different tables with their corresponding radio/infrared and X-ray properties.
These tables are intended as a useful tool for researchers interested in particular identifications. 相似文献
126.
Essential macroscopic internal properties of compact objects can be related to each other with the help of General Relativity.
A somewhat familiar example is the relationship between the compactness M/R and the gravitational redshift for nonrotating bodies. Rotation poses new challenges when trying to relate observed or potentially
observed quantities such as the graviational redshift, mass, radius, and angular velocity. Using a perturbative approach,
we present an analytical approximation whose purpose is to relate these quantities. Two main results are highlighted: Derivation
of a new maximal angular velocity depending only on the mass of the object and a possible estimate of the radius from a measurement
of the gravitational redshift. 相似文献
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128.
Doris Barboni Gail M. Ashley Manuel Dominguez-Rodrigo Henry T. Bunn Audax Z.P. Mabulla Enrique Baquedano 《Quaternary Research》2010,74(3):344-354
The phytolith content of 10 samples collected immediately under Tuff IF (~ 1.785 Ma) at FLK N and other surrounding localities (~ 2 km²) provides a direct botanical evidence for woody vegetation in the eastern margin of Olduvai Gorge during uppermost Bed I time. Observation and counting of 143 phytolith types (5 to >150 μ) reveal dense but heterogeneous woody cover (~ 40–90%) of unidentified trees and/or shrubs and palms associated to the freshwater springs surrounding FLK N, and more open formation (presumably ~ 25–70% woody cover) in the southeast at localities VEK, HWK W and HWK E. The paleovegetation is best described as groundwater palm forest/woodland or bushland, which current analogue may be found near Lake Manyara in similar hydrogeological context (freshwater springs near saline/alkaline lake). Re-evaluating the published pollen data based on this analogy shows that 70% of the pollen signal at FLK N may be attributed to thicket-woodland, Acacia groundwater woodland, gallery and groundwater forests; while < 30% is attributed to swamp herbage and grasslands. Micro-botanical, isotopic, and taphonomical studies of faunal remains converge on the same conclusion that the area surrounding FLK N, which attracted both carnivores and hominins in the early Pleistocene, was densely wooded during uppermost Bed I time. 相似文献
129.
The southeast area of the Argentine Pampas is characterized by the presence of an unconfined aquifer in a wide plain. A methodology is proposed that deals with the aquifer vulnerability where the homogeneity of the hydrogeological variables used by traditional methods (in this case, DRASTIC-P) causes vulnerability maps to show more than 80% of the territory under the same class. This absence of discrimination renders vulnerability maps of little use to decision-makers. In addition, the proposed methodology avoids the traditional vague classification (high, low, and moderate vulnerability) which is highly dependent on subjectivity in its association of each class with hydrogeological considerations. That traditional vulnerability assessment methodology was adapted using a geographic information system to reclassify classes, based on the Natural Breaks (Jenks) method. The pixel-to-pixel comparison between the result obtained by the DRASTIC-P and the reclassified classes generates the so-called operational vulnerability index (OVI), which shows four classes, associating each with different hydrogeological requirements to make decisions. 相似文献
130.
Gabriel Auvinet-Guichard Juan F. Rodríguez-Rebolledo José L. Rangel-Núñez 《Acta Geotechnica》2010,5(1):63-68
The drainage system of Mexico City, one of the largest metropolitan areas in the world, is formed by a large network of interceptors
and collectors leading to the main outlet: a 49.3-km-long tunnel with a 6.5 m diameter. To build the access shafts to the
tunnels of the system and the deep sumps of the pumping stations in the very soft clays of the lacustrine area of Mexico valley,
a technique known as “flotation method” has been commonly used since 1969. The paper presents the main construction steps
followed and some aspects of the analysis and design of shafts constructed by this technique. The experience gained obtained
after more than 30 shafts have been constructed by this method, and the actual trends in its application are also discussed. 相似文献