The distribution of supermassive black holes in the nuclei of nearby galaxies     

Andrea Cattaneo  Martin G. Haehnelt  Martin J. Rees 《Monthly notices of the Royal Astronomical Society》1999,308(1):77-81

The growth of supermassive black holes by merging and accretion in hierarchical models of galaxy formation is studied by means of Monte Carlo simulations. A tight linear relation between masses of black holes and masses of bulges arises if the mass accreted by supermassive black holes scales linearly with the mass-forming stars and if the redshift evolution of mass accretion tracks closely that of star formation. Differences in redshift evolution between black hole accretion and star formation introduce a considerable scatter in this relation. A non-linear relation between black hole accretion and star formation results in a non-linear relation between masses of remnant black holes and masses of bulges. The relation of black hole mass to bulge luminosity observed in nearby galaxies and its scatter are reproduced reasonably well by models in which black hole accretion and star formation are linearly related but do not track each other in redshift. This suggests that a common mechanism determines the efficiency for black hole accretion and the efficiency for star formation, especially for bright bulges.  相似文献   

An application of the Kerr black hole fly-wheel model to statistical properties of QSOs/AGNs     

Shin-ya Nitta 《Monthly notices of the Royal Astronomical Society》1999,308(4):995-1005

The aim of this work is to demonstrate the properties of the magnetospheric model around Kerr black holes (BHs), the so-called fly-wheel (rotation driven) model. The fly-wheel engine of the BH–accretion disc system is applied to the statistics of QSOs/AGNs. In the model, the central BH is assumed to be formed at z ∼10² and obtains nearly maximum but finite rotation energy (∼extreme Kerr BH) at the formation stage. The inherently obtained rotation energy of the Kerr BH is released through a magnetohydrodynamic process. This model naturally leads to a finite lifetime of AGN activity.
Nitta, Takahashi & Tomimatsu clarified the individual evolution of the Kerr BH fly-wheel engine, which is parametrized by BH mass, initial Kerr parameter, magnetic field near the horizon and a dimensionless small parameter. We impose a statistical model for the initial mass function (IMF) of an ensemble of BHs using the Press–Schechter formalism. With the help of additional assumptions, we can discuss the evolution of the luminosity function and the spatial number density of QSOs/AGNs.
By comparing with observations , it is found that a somewhat flat IMF and weak dependence of the magnetic field on the BH mass are preferred. The result explains well the decrease of very bright QSOs and decrease of population after z ∼2.  相似文献   

Computation of mass outflow rate from relativistic quasi-spherical accretion on to black holes     

Tapas K. Das 《Monthly notices of the Royal Astronomical Society》1999,308(1):201-206

We compute the mass outflow rate R _m˙ from relativistic matter that is accreting quasi-spherically on to the Schwarzschild black holes. Taking the pair-plasma pressure-mediated shock surface as the effective boundary layer (of the black hole) from where the bulk of the outflow is assumed to be generated, computation of this rate is done using combinations of exact transonic inflow and outflow solutions. We find that R _m˙ depends on the initial parameters of the flow, the polytropic index of matter, the degree of compression of matter near the shock surface and the location of the shock surface itself. We thus not only study the variation of the mass outflow rate as a function of various physical parameters governing the problem, but also provide a sufficiently plausible estimation of this rate.  相似文献   

Magnitude of lateral displacement on the Crevillente Fault Zone (Betic Cordillera,SE Spain): stratigraphical and sedimentological considerations     

L. M. Nieto  J. Rey 《Geological Journal》2004,39(1):95-110

The Crevillente Fault Zone (CFZ) comprises a system of northeast to southwest oriented dextral faults that extend for some 600 km in the External Zones of the Betic Cordillera (SE Spain). The magnitude of lateral displacement related to this fault zone is not well constrained, and it is considered to be between 20 and 400 km. The stratigraphical and sedimentological criteria used in this work have proven effective in quantifying the magnitude of the displacement along this structure. We have analysed an oolitic turbidite facies in the Middle Jurassic of the Sierra de Ricote (Median Subbetic of Murcia Province). A detailed revision of ooidal limestone outcrops has revealed that the source area of these deposits was to the Internal Subbetic zone, north of Vélez Rubio (Almería Province). These two tectonic units, the Median and Internal Subbetic, are currently 75 km from each other and separated by the CFZ. The conclusions arising from our stratigraphical, petrological and sedimentological studies favour interpretation of a 75–100 km lateral displacement. After restoring the Late Jurassic–Cretaceous anticlockwise rotation of Iberia, the CFZ appears to belong to the E–W palaeofault system that is related to the extension of the South Iberian Continental Margin (SICM). Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

顺序扫描ICP—AES法测定海洋沉积物中九种主要成分   总被引：2，自引：0，他引：2  

张爱滨  金红 《海洋湖沼通报》1998,(3):24-28

用ICP—AES法测定海洋沉积物中铝、铁、钙、镁、钠、钾、钦、锰、磷等九种主要成分,方法简便,省时省力,测量精密度小于4％,可以满足海洋地球化学的要求。  相似文献   

琼州海峡南岸海岸动力地貌研究     

陈沈良 《热带海洋学报》1998,(3)

岬湾相间的琼州海峡南岸在海岸动力条件作用下,岸滩发生侵蚀或堆积,特别是南岸中部的南渡江三角洲沿岸岸滩演变剧烈。该文从海岸动力地貌的角度,对琼州海峡南岸的海岸动力特征、泥沙运动以及岸滩演变进行分析。根据海峡南部三维潮流场数值模拟结果,结合经验公式初步分析潮流引起的泥沙运移速率和方向,得到岸外水域总的泥沙运移趋势为从西向东。根据波浪动力计算分析沿岸泥沙运移,探讨沙质岸滩的动态与地貌演变之间的关系,得出海峡南岸海岸地貌演变与盛行的NE和NNE向风浪有密切关系,岸滩的演变过程主要受制于这两个方向的风浪及其引起的泥沙沿岸运移。  相似文献   

南黄海的海底侵蚀作用   总被引：3，自引：0，他引：3  

申顺喜  李安春  姜学钧  袁巍 《海洋与湖沼》1998,29(5):542-546

１９９２年５月－１９９３年１０月期间,在南黄海及东海北部海域,利用大洋５０型表层取样器,重力活塞取样及底栖拖网等方法,对海底沉积进行了深入的调查,通过对所获样品的粒度,矿物含量,生物组合及年代地层学多学科综合性的分析研究表明,南黄海及东海北部陆架的沉积环境十分复杂,在南黄海高能侵蚀区海底广泛出露砂质沉积物,其分布范围与强潮夕及风暴潮的活动区相一致,在这些水动力的长期作用下,细粒物质逐渐被悬浮,搬运  相似文献   

海坛岛海域表层沉积物中主量化学成分的地球化学   总被引：1，自引：0，他引：1  

杨慧辉  陈岚 《海洋学报》1998,20(3):47-55

本文对海坛岛海域３３个表层沉积物中１０种化学成分的含量、含量变化和区域平面分布作了描述和探讨。化学成分中Ｃｏｒｇ、Ｎ、Ｐ、Ｆｅ、ＡＩ、Ｔｉ、Ｍｇ等元素的关性好,和粘土矿物关系密切,从陆源搬运入海;Ｃａ、碳酸盐和上述及粘土含量呈负相关,在富含生物介壳的粗粒沉积中富集;Ｍｎ主要赋存于陆源碎屑,而在砾砂中有自生Ｍｎ沉积。Ｑ型聚类分析的结果表明,调查区可分为３个地球化学分区,综合反映了沉积物的地球化学特征。  相似文献   

椒江河口浮泥的分布和调整   总被引：7，自引：3，他引：4  

李炎  夏小明  董礼先 《海洋学报》1998,20(4):72-82

应用光学和声学泥沙剖面监测系统,进行1991、1994和1995年3个航次的椒江河口最大混浊带纵横剖面和时间剖面观测.在受控于潮流和径流对比条件的周期性调整基础上,椒江河口浮泥层还表现出非主流聚集趋向和洼地聚集趋向,促使最大混浊带保持对边界条件十分敏感的泥沙储库.  相似文献   

Numerical studies of upwelling in coastalareas of the East China Sea——Ⅰ The tide-induced upwelling     

Luo Yiyong  Yu Guangyao  Huang Zuke 《海洋学报(英文版)》1998,17(1):15-25

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