ΛCDM predictions for galaxy protoclusters – I. The relation between galaxies, protoclusters and quasars at  z∼ 6      

Roderik A. Overzier  Qi Guo  Guinevere Kauffmann  Gabriella De Lucia  Rychard Bouwens  Gerard Lemson 《Monthly notices of the Royal Astronomical Society》2009,394(2):577-594

Motivated by recent observational studies of the environment of   z ∼ 6  QSOs, we have used the Millennium Run (MR) simulations to construct a very large  (∼4°× 4°)  mock redshift survey of star-forming galaxies at   z ∼ 6  . We use this simulated survey to study the relation between density enhancements in the distribution of i ₇₇₅-dropouts and Lyα emitters, and their relation to the most massive haloes and protocluster regions at   z ∼ 6  . Our simulation predicts significant variations in surface density across the sky with some voids and filaments extending over scales of 1°, much larger than probed by current surveys. Approximately one-third of all   z ∼ 6  haloes hosting i -dropouts brighter than   z = 26.5  mag  (≈ M *_{UV, z =6})  become part of   z = 0  galaxy clusters. i -dropouts associated with protocluster regions are found in regions where the surface density is enhanced on scales ranging from a few to several tens of arcminutes on the sky. We analyse two structures of i -dropouts and Lyα emitters observed with the Subaru Telescope and show that these structures must be the seeds of massive clusters in formation. In striking contrast, six   z ∼ 6  QSO fields observed with Hubble Space Telescope show no significant enhancements in their i ₇₇₅-dropout number counts. With the present data, we cannot rule out the QSOs being hosted by the most massive haloes. However, neither can we confirm this widely used assumption. We conclude by giving detailed recommendations for the interpretation and planning of observations by current and future ground- and space-based instruments that will shed new light on questions related to the large-scale structure at   z ∼ 6  .  相似文献   

Milky Way type galaxies in a ΛCDM cosmology     

Maria E. De Rossi  Patricia B. Tissera  Gabriella De Lucia †  Guinevere Kauffmann 《Monthly notices of the Royal Astronomical Society》2009,395(1):210-217

We analyse a sample of 52 000 Milky Way (MW) type galaxies drawn from the publicly available galaxy catalogue of the Millennium Simulation with the aim of studying statistically the differences and similarities of their properties in comparison to our Galaxy. Model galaxies are chosen to lie in haloes with maximum circular velocities in the range 200–250 km s⁻¹ and to have bulge-to-disc ratios similar to that of the MW. We find that model MW galaxies formed 'quietly' through the accretion of cold gas and small satellite systems. Only ≈12 per cent of our model galaxies experienced a major merger during their lifetime. Most of the stars formed ' in situ ', with only about 15 per cent of the final mass gathered through accretion. Supernovae (SNe) and active galactic nuclei (AGN) feedback play an important role in the evolution of these systems. At high redshifts, when the potential wells of the MW progenitors are shallower, winds driven by SNe explosions blow out a large fraction of the gas and metals. As the systems grow in mass, SNe feedback effects decrease and AGN feedback takes over, playing a more important role in the regulation of the star formation activity at lower redshifts. Although model MW galaxies have been selected to lie in a narrow range of maximum circular velocities, they nevertheless exhibit a significant dispersion in the final stellar masses and metallicities. Our analysis suggests that this dispersion results from the different accretion histories of the parent dark matter haloes. Statistically, we also find evidences to support the MW as a typical Sb/Sc galaxy in the same mass range, providing a suitable benchmark to constrain numerical models of galaxy formation.  相似文献   

Uranium and microcracks in a 1,000-meter core,Redstone, New Hampshire     

Louis Caruso  Gene Simmons 《Contributions to Mineralogy and Petrology》1985,90(1):1-17

The spatial distribution and mineralogical association of uranium in 30 samples of a 1,000 meter core from the Redstone (NH) Quarry were examined with fission track techniques, backscattered electron imaging, and energy dispersive X-ray spectrometry with the following results for the Conway and Mount Osceola granites: (1) Uranium occurs in microcracks sealed with siderite and/or with Ca+ RE fluorocarbonate minerals; the uranium contents of siderite and the RE fluorocarbonates are 1 to 30 ppm and 500–1,500 ppm, respectively. (2) Siderite and to a lesser extent RE fluorocarbonate minerals occur as replacement minerals of amphibole and biotite; the RE fluorocarbonates are the main alteration minerals of allanite. (3) The degree of alteration and the extent of uranium redistribution are greater in samples with major uraniferous microcracks. (4) The contents of Ca and Mn are approximately constant for siderite in sealed cracks throughout the Conway and Mount Osceola granites for the entire section penetrated by the corehole, approximately 700 meters. — From these observations, we conclude that an extensive set of fractures throughout a significant volume of the Mount Osceola and Conway granties were the conduits through which hydrothermal fluids containing CO₂, uranium, and REs circulated. Microcracks facilitated fluid-rock interactions resulting in alteration and uranium redistribution. Certain primary uraniferous accessory minerals, i.e., allanite and ilmenorutile may have been the source for at least part of the uranium and REs that now occur in secondary minerals in these granites.  相似文献   

Frequency dependence of site amplification factor in the Messina Strait area     

M. L. Alonzo  A. Bottari  V. Caruso  C. Godano 《Pure and Applied Geophysics》1993,140(3):415-426

The spectral ratio method is used here for evaluating the frequency dependence of a site amplification factor in the Messina Strait area. All stations exhibit the same features of spectral ratios evidencing two peaks at about 10 Hz and 16 Hz. We relate this observation to the same geological structures. In fact, all the stations (except the referenced one) are situated over pleistocenic sediments with a similar grain size. This causes the disappearing of any site effect when the average spectrum is used as a reference. MES station, situated in the city of Messina, presents a clear site effect at a different frequency (6 Hz) which cannot be related to any geological structure because no substantial difference is observed between the sediments on which this station is situated and the sediments on which the other stations are situated. MT1 station exhibits a spectral peak at about 2 Hz which can be explained with oscillations of a little sedimentary basin.  相似文献   

Heterotrophic bacteria in the northern Adriatic Sea: seasonal changes and ectoenzyme profile   总被引：1，自引：0，他引：1  

Zaccone R  Caruso G  Calì C 《Marine environmental research》2002,54(1):1-19

A seasonal study of the quantitative and qualitative distribution of heterotrophic bacterial community was carried out in the Adriatic Sea between April 1995 and January 1996, in order to evaluate its spatial and temporal variability and metabolic potential in the degradation processes of organic matter. The culturable bacteria (CFU) ranged between 0.1 and 22% of total bacterioplankton with a maximum percentage in surface samples of coastal zones. Their distribution was generally affected by the prevailing hydrological conditions. At the coastal stations about 44-75% of CFU variance could be explained by river runoff. The changes in the composition of heterotrophic bacterial community showed a seasonal succession of main bacterial groups, with a prevalence of Gram negative, non fermenting bacteria in the cold period (April-January) and an increase of Vibrionaccae and pigmented bacteria in summer. The seasonal variations were more important at the stations influenced by rivers than offshore. The bacterial community showed a greater versatility for organic polymers hydrolysis in the offshore station than in the coastal areas. Over 60% of all isolated heterotrophic bacteria expressed peptidase, lipase and phosphatase ectoenzymes activities, in all seasons and showed an increasing trend in warm period (in July October). The alpha- and beta-glucosidase potentials of bacteria were lower (20% on average) and showed different pattern during the year. These results suggest different role of the bacterial community in the decomposition of organic matter in the Adriatic Sea. Since only 20% of bacterial strains expressed glucosidase activity, carbohydrate-rich polymers such as mucilage might accumulate.  相似文献   

Substructure in lensing clusters and simulations     

Priyamvada Natarajan  Gabriella De Lucia  Volker Springel 《Monthly notices of the Royal Astronomical Society》2007,376(1):180-192

  相似文献   

GRIDA3—a shared resources manager for environmental data analysis and applications     

Fabrizio Murgia  Riccardo Biddau  Alessandro Concas  Roberto Demontis  Luca Fanfani  Zeno Heilmann  Cristian Lai  Giuditta Lecca  Eva Lorrai  Marino Marrocu  Vittorio Alessandro Marrone  Laura Muscas  Elisaveta Peneva  Andrea Piras  Massimo Pisu  Gabriella Pusceddu  Guido Satta  Daniela Theis  Andrea Vacca  Paolo Valera  Ana Melina Vallenilla Ferrara  Ernesto Bonomi 《Earth Science Informatics》2009,2(1-2):5-21

GRIDA3 (Shared Resources Manager for Environmental Data Analysis and Applications) is a multidisciplinary project designed to deliver an integrated system to forge solutions to some environmental challenges such as the constant increase of polluted sites, the sustainability of natural resources usage and the forecast of extreme meteorological events. The GRIDA3 portal is mainly based on Web 2.0 technologies and EnginFrame framework. The portal, now at an advanced stage of development, provides end-users with intuitive Web-interfaces and tools that simplify job submission to the underneath computing resources. The framework manages the user authentication and authorization, then controls the action and job execution into the grid computing environment, collects the results and transforms them into an useful format on the client side. The GRIDA3 Portal framework will provide a problem-solving platform allowing, through appropriate access policies, the integration and the sharing of skills, resources and tools located at multiple sites across federated domains.  相似文献   

芙蓉统和排碧阶底界全球层型剖面的牙形刺生物地层   总被引：3，自引：3，他引：0  

祁玉平  王志浩 《地层学杂志》2004,28(2):114-119

寒武系芙蓉统和排碧阶全球层型剖面——湖南花垣排碧剖面底界界线层的牙形刺生物地层,由下至上划分为Westergaardodina tetragonia带、Westergaardodina matsushitai带和Westergaardodina bicuspidate 3个牙形刺带,可与该界线层的三叶虫带进行很好对比;同时讨论了芙蓉统和排碧阶底界划在牙形刺Westergaardodina mat-sushitai带和Westergaardodina bicuspidata带之间的合理性;此外,还将该牙形刺分带与华北和东北地区寒武系牙形刺带进行了对比。  相似文献   

Lethal and estrogenic effects of 4-nonylphenol in the cockle Cerastoderma glaucum     

Marin MG  Rigato S  Ricciardi F  Matozzo V 《Marine pollution bulletin》2008,57(6-12):552-558

The lethal and sublethal effects of the xenoestrogen 4-nonylphenol (NP) were evaluated in the cockle Cerastoderma glaucum. In a 96-h lethality test, bivalves were exposed to 0, 0+ acetone, 0.19, 0.38, 0.75, 1.5 and 3.0 mg NP/l. The 96-h LC(50) value was 0.3mg NP/l. No mortality was observed at 0.1 mg NP/l. The potential estrogenicity of NP was studied in both sexually undifferentiated (resting phase) and differentiated (pre-spawning phase) cockles, exposed for 7 and 14 days to 0, 0+ acetone, 0.0125, 0.025, 0.05, and 0.1 mg NP/l. Vitellogenin (Vg)-like protein levels were determined in both haemolymph and digestive gland by the alkali-labile phosphate (ALP) assay. In the resting phase, exposure for 7 days to 0.1 mg NP/l resulted in significant increases in ALP in both haemolymph and digestive gland, compared with controls. A significant increase was also observed in digestive gland of animals exposed to 0.0125 mg NP/l-exposed animals. After 14 days of exposure, haemolymph ALP levels were significantly increased in exposed animals at all NP concentrations tested, whereas no difference was recorded in digestive gland. In the pre-spawning phase, exposure for 7 days to NP significantly increased ALP levels in haemolymph from males exposed at all NP concentrations tested, whereas no significant variations were found in haemolymph from females. NP (0.05 and 0.1 mg/l) was also shown to increase ALP concentrations significantly in digestive gland of males, but not in those of females. Likewise, after 14 days' exposure, ALP levels significantly increased in haemolymph from males only at 0.1 mg NP/l. Conversely, NP caused significant increases in ALP levels in digestive gland from both males (at all NP concentrations tested) and females (at 0.025 and 0.1 mg NP/l). These results demonstrate that NP induces Vg synthesis in C. glaucum. Interestingly, males were more responsive to NP than females.  相似文献   

Proposed GSSP for the base of Cambrian Stage 9, coinciding with the first appearance of Agnostotes orientalis, at Duibian, Zhejiang, China     

Loren E. BABCOCK  Gabriella BAGNOLI 《中国科学D辑(英文版)》2009,(4)

Exposed in natural outcrops near the Duibian Village, Jiangshan County, Zhejiang Province, China, the Duibian B section is proposed as the boundary stratotype for the base of an unnamed stage termed provisionally Cambrian Stage 9. The proposed position of the GSSP is 108.12 m above the base of the Huayansi Formation, at a horizon coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalis. This horizon coincides also with the first appearance of the cosmopoli-tan polym...  相似文献