Dissipationless mergers of elliptical galaxies and the evolution of the fundamental plane     

Michael Boylan-Kolchin  Chung-Pei Ma  Eliot Quataert 《Monthly notices of the Royal Astronomical Society》2005,362(1):184-196

We carry out numerical simulations of dissipationless major mergers of elliptical galaxies using initial galaxy models that consist of a dark matter haloes and a stellar bulge with properties consistent with the observed fundamental plane. By varying the density profile of the dark matter haloes [standard Navarro, Frenk & White (NFW) profile versus adiabatically contracted NFW profile], the global stellar to dark matter mass ratio and the orbit of the merging galaxies, we are able to assess the impact of each of these factors on the structure of the merger remnant. Our results indicate that the properties of the remnant bulge depend primarily on the angular momentum and energy of the orbit; for a cosmologically motivated orbit, the effective radius and velocity dispersion of the remnant bulge remain approximately on the fundamental plane. This indicates that the observed properties of elliptical galaxies are consistent with significant growth via late dissipationless mergers. We also find that the dark matter fraction within the effective radius of our remnants increases after the merger, consistent with the hypothesis that the tilt of the fundamental plane from the virial theorem is due to a varying dark matter fraction as a function of galaxy mass.  相似文献   

Organic carbon deposition and phosphorus accumulation during Oceanic Anoxic Event 2 in Tarfaya, Morocco     

Haydon P. Mort  Thierry Adatte  Gerta Keller  David Bartels  Karl B. Fllmi  Philipp Steinmann  Zsolt Berner  E.H. Chellai 《Cretaceous Research》2008,29(5-6):1008

With a multi-proxy approach, an attempt was made to constrain productivity and bottom-water redox conditions and their effects on the phosphorus accumulation rate at the Mohammed Plage section on the Tarfaya coast, Morocco, during the Cenomanian-Turonian Anoxic Event (OAE 2). A distinct δ¹³C_org isotope excursion of +2.5‰ occurs close to the top of the section. The unusually abrupt shift of the isotope excursion and disappearance of several planktonic foraminiferal species (e.g. Rotalipora cushmani and Rotalipora greenhornensis) in this level suggests a hiatus of between 40–60 kyrs at the excursion onset. Nevertheless, it was possible to determine both the long-term environmental history as well as the processes that took place immediately prior to and during OAE 2. TOC% values increase gradually from the base of the section to the top (from 2.5% to 10%). This is interpreted as the consequence of a long-term eustatic sea-level rise and subsidence causing the encroachment of less oxic waters into the Tarfaya Basin. Similarly a reduction in the mineralogically constructed ‘detrital index’ can be explained by the decrease in the continental flux of terrigenous material due to a relative sea-level rise. A speciation of phosphorus in the upper part of the section, which spans the start and mid-stages of OAE 2, shows overall higher abundances of P_reactive mass accumulation rates before the isotope excursion onset and lower values during the plateau. Due to the probable short hiatus, the onset of the decrease in phosphorus content relative to the isotope excursion is uncertain, although the excursion plateau already contains lower concentrations. The C_org/P_total and V/Al ratios suggest that this reduction was mostly likely caused by a decrease in the available bottom oxygen content (probably as a result of higher productivity) and a corresponding fall in the phosphorus retention ability of the sediment. Productivity appears to have remained high during the isotope plateau possibly due to a combination of ocean-surface fertilisation via increased aridity (increased K/Al and Ti/Al ratios) and/or higher dissolved inorganic phosphorus content in the water column as a result of the decrease in sediment P retention. The evidence for decreased P-burial has been observed in many other palaeoenvironments during OAE 2. Tarfaya's unique upwelling paleosituation provides strong evidence that the nutrient recycling was a global phenomenon and therefore a critical factor in starting and sustaining OAE 2.  相似文献   

Calcareous nannoplankton, planktonic foraminiferal, and carbonate carbon isotope stratigraphy of the Cenomanian–Turonian boundary section in the Ultrahelvetic Zone (Eastern Alps, Upper Austria)     

Michael Wagreich  Ana-Voica Bojar  Reinhard F. Sachsenhofer  Stephanie Neuhuber  Hans Egger 《Cretaceous Research》2008,29(5-6):965

Ultrahelvetic units of the Eastern Alps were deposited on the distal European continental margin of the (Alpine) Tethys. The Rehkogelgraben section (“Buntmergelserie”, Ultrahelvetic unit, Upper Austria) comprises a 5 m thick succession of upper Cenomanian marl-limestone cycles overlain by a black shale interval composed of three black shale layers and carbonate-free claystones, followed by lower Turonian white to light grey marly limestones with thin marl layers. The main biostratigraphic events in the section are the last occurrence of Rotalipora and the first occurrences of Helvetoglobotruncana helvetica and Quadrum gartneri. The thickest black shale horizon has a TOC content of about 5%, with predominantly marine organic matter of kerogen type II. Vitrinite reflectance and Rock-Eval parameter T_max (<424 °C) indicate low maturity. HI values range from 261 to 362 mg HC/g TOC. δ¹³C values of bulk rock carbonates display the well documented positive shift around the black shale interval, allowing correlation of the Rehkogelgraben section with other sections such as the Global Boundary Stratotype Section and Point (GSSP) succession at Pueblo, USA, and reference sections at Eastbourne, UK, and Gubbio, Italy. Sediment accumulation rates at Rehkogelgraben (average 2.5 mm/ka) are significantly lower than those at Pueblo and Eastbourne.  相似文献   

沉积盆地有机质自由基热演化特征及其作为古温标的探索   总被引：1，自引：0，他引：1  

徐二社  邱楠生  秦建中  郑伦举 《地质学报》2008,82(3):413-419

恢复沉积盆地热历史的方法主要有古地温指标法和动力学模拟法两类.古温标法中最常用的为有机质成熟度和矿物裂变径迹,动力学模拟法中最常用的是盆地的拉张模型和挤压模型.本文针对Ⅰ型有机质自由基浓度作为沉积盆地古温标进行了探索研究.分析了自然演化系列Ⅰ型有机质的自由基的热演化特征;根据自然演化系列的Ⅰ型有机质自由基浓度及时间-温度指数(TTI)数据,对热模拟实验下的Ⅰ型有机质自由基浓度及时间-温度指数(TTI)值进行校正,由校正后的数据初步建立了Ⅰ型有机质的自由基浓度(Ng)与时间-温度指数(TTI)的定量模型.  相似文献   

冀北—辽西早白垩世沉积有机质特征与古气候环境演变     

李洪涛  宋之光  邹艳荣  王成善  季强 《地质学报》2008,82(1):72-76

本文对冀北—辽西地区早白垩世沉积盆地富有机质沉积岩进行了初步有机地球化学分析研究。结果显示,冀北—辽西沉积盆沉积有机质特征在时间和空间上存在很大差异,代表白垩系早期沉积的滦平盆地大北沟组有机质丰度低,这不仅显示其所代表的沉积相带不利于有机质的聚集,也反映了当时生物不够繁盛;大店子组时期沉积相带发生了变化,有机质类型随着发生了变化,丰度有所增高,但总体上显示环境条件不利于生物的发育和繁盛。到了桥头组和义县组沉积岩有机质丰度大幅升高,表明生物界非常繁盛,古气候环境有利于有机质的大量生成和堆积,总体上反映了温湿的气候条件;但同时也存在较为频繁或交替性寒冷气候波动,具体的古气候环境状态尚需进一步深入研究。  相似文献   

藏南白垩系黑-红层沉积岩有机质组成分布特征   总被引：1，自引：0，他引：1  

傅培刚  宋之光  胡修棉  王成善 《地质学报》2008,82(1):85-91

对藏南江孜县床得剖面白垩系黑层和红层沉积岩进行的有机地球化学研究表明,黑层有机碳含量高于红层5～10倍,红层和黑层饱和烃主峰碳数分别为nC25和nC23;黑层和红层沉积有机质的母质来源都以水生植物和菌藻类等低等生物为主,陆源有机质的输入非常有限;但饱和烃的分布和主峰碳数的差异可能反映了有机母源物质在种群方面的差异,而这种差异可能主要是水体温度存在差异造成的,即红层发育时期水体温度可能高于黑层沉积时期.而在高温度条件下,水生生物和陆生植物的生长发育受到限制,造成原始有机质产率和有机质沉积保存量低可能是红层沉积岩形成的主要原因.  相似文献   

Correlations between heavy metals and organic carbon extracted by dry oxidation procedure in urban roadside soils   总被引：1，自引：0，他引：1  

Xue Song Wang 《Environmental Geology》2008,54(2):269-273

The organic fraction in soils has a significant influence on heavy metal transport. In this study, the organic carbon content was measured by dry oxidation procedure from 21 Xuzhou urban roadside soils to assess the relationships between the concentrations of heavy metals (Pb, Cu, Zn, and Cr) and the amount of organic carbon. The anthropogenic heavy metals (e.g. Pb, Cu, Zn) were strongly correlated with organic carbon (denoted by C_org−c) extracted by dry oxidation while natural heavy metal (e.g. Cr) showed no correlation to the C_org−c. The anthropogenic heavy metals were also strongly correlated with the amount of the total carbon. These results show that the anthropogenic heavy metals are mainly enriched in the organic matter in the Xuzhou urban roadside soils.  相似文献   

Impact of lightning on organic matter-rich soils: influence of soil grain size and organic matter content on underground fires     

Vittorio Zanon  Fátima Viveiros  Catarina Silva  Ana Rita Hipólito  Teresa Ferreira 《Natural Hazards》2008,45(1):19-31

A detailed study was carried out on a piece of land that had been struck by lightning during the violent rainstorm that raged over the Island of S?o Miguel (Azores Archipelago) in late October 2006. Temperature and gas measurements (CO₂, CO, H₂S and CH₄) were performed in four study trenches, dug in an area of ∼3 m², where an underground fire had been initiated by the impact with a lightning stroke, followed by the emission of a column of gases and smoke. The soil under study was originally a well-pedogenized about 80 cm thick bed, made of volcanic clayey to silty tephra fallouts and contained 5.5–9.7% of organic matter. The underground fire was monitored for one week and revealed a peak release of 404 ppm CO and 3.4% CO₂ originating from a horizon located about 45 cm under the soil surface. Measurements of temperature, performed one week after the impact, indicated a maximum value of 326°C inside the soil, while 516.5°C were measured on the surface of a lava block interred about 20 cm under the surface. Subsequently, a stratigraphic and sedimentologic study proved the role of the grain-size of the soil and of the organic matter content of the different horizons of the impact area, in determining the ratio between anoxic/oxidised combustion conditions and in the progress of the process itself. It was also noticed that combustion was not total all over in the soil bed and that the process had slightly migrated toward SW during the observation period. The combustion process went on for about ten days, in spite of several other violent rainstorms, until it was artificially extinguished through the excavations made to obtain study trenches. This particular circumstance evidenced the potential natural hazard represented by this kind of atmospheric event, especially in a land where the volcanic nature of the soil may easily mislead inexperienced observers and, consequently, delay proper action.  相似文献   

渤海海洋线虫与底栖桡足类数量之比的应用研究   总被引：9，自引：0，他引：9  

郭玉清  张志南  慕芳红 《海洋科学》2002,26(12):27-31

在渤海的22个站位，分3个航次采集未受扰动的沉积物样品，进行了小型底栖动物中两个主要类群自由生活海洋线虫和底栖桡足类数量变动和两者数量之比评价沉积物有机污染环境的研究。结果表明：对于同一航次的不同重复，数量变动差异显著或极显著；在同一个站位24h，6次重复取样，两者数量的变异系数较大；在应用该比值进行沉积物有机污染评价时，在同一站位该比值波动较大。  相似文献   

渤海中南部悬浮物海洋调查资料分析   总被引：6，自引：0，他引：6  

苏健  江文胜  孙文心 《中国海洋大学学报(自然科学版)》2001,31(5):647-652

对于悬浮物 (SPM)的研究目前已引起诸多学者关注。作者利用 1998和 1999年的中德合作海洋调查所获得的资料进行分析。主要进行三个方面的工作 :研究悬浮物与透明度的关系 ;研究悬浮物与浊度的关系 ;估计海底剪切速度。并为研究悬浮物输运提供资料和作前期研究  相似文献