Confusion noise at far-infrared to millimetre wavelengths     

M. Negrello  M. Magliocchetti  L. Moscardini  G. De Zotti  G. L. Granato  L. Silva 《Monthly notices of the Royal Astronomical Society》2004,352(2):493-500

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A source of high-velocity white dwarfs     

Melvyn B. Davies  rew King  Hans Ritter 《Monthly notices of the Royal Astronomical Society》2002,333(2):463-468

We investigate whether the recently observed population of high-velocity white dwarfs can be derived from a population of binaries residing initially within the thin disc of the Galaxy. In particular, we consider binaries where the primary is sufficiently massive to explode as a Type II supernova. A large fraction of such binaries are broken up when the primary then explodes as a supernova, owing to the combined effects of the mass loss from the primary and the kick received by the neutron star on its formation. For binaries where the primary evolves to fill its Roche lobe, mass transfer from the primary leads to the onset of a common envelope phase during which the secondary and the core of the primary spiral together as the envelope is ejected. Such binaries are the progenitors of X-ray binaries if they are not broken up when the primary explodes. For those systems that are broken up, a large number of the secondaries receive kick velocities ∼100–200 km s⁻¹ and subsequently evolve into white dwarfs. We compute trajectories within the Galactic potential for this population of stars and relate the birth rate of these stars over the entire Galaxy to those seen locally with high velocities relative to the local standard of rest (LSR) . We show that for a reasonable set of assumptions concerning the Galactic supernova rate and the binary population, our model produces a local number density of high-velocity white dwarfs compatible with that inferred from observations. We therefore propose that a population of white dwarfs originating in the thin disc may make a significant contribution to the observed population of high-velocity white dwarfs.  相似文献   

Edge-on boxy profiles in non-barred disc galaxies     

P. A. Patsis  E. Athanassoula  P. Grosbøl  Ch. Skokos 《Monthly notices of the Royal Astronomical Society》2002,335(4):1049-1053

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大地构造和海陆起源的内波假说（Ⅰ）──关于板块学说的若干问题及其思考     

池顺良  锤荣融  杨洪之  骆鸣津 《大地测量与地球动力学》1996,(1)

随着资料的积累，不断发现与板块假说相矛盾的事实：地震层析没有发现地幔对流的证据，却发现大陆克拉通具有４００ｋｍ深的“壳根”；海洋地质调查发现了一系列否定板块假说的重要证据，尤其是大西洋中多处发现古岩石，使海底扩张模型受到严重挑战；跨越扩张脊的一系列测量结果实际上否定了扩张假说。此外，作为学说重要支柱的地磁资料的可靠性受到怀疑，板块消减过程中洋底沉积层堆积被否定，大陆碰撞模式与陆上地质资料的不符，动力机制不明，板块模式不适于解释复杂的大陆地质而难以登陆等事实，已令板块构造理论陷入了深刻的危机之中。根据煤和蒸发岩的地史分布等资料，说明一个海陆相对固定的大地构造模型更符合实际。通过对大地构造假说发展史的分析和研究，并借鉴天文学中太阳系的发现史，认为新假说的建立必须从确凿的地质现象，而非多解性的资料和推断出发。由此提出大地构造和海陆起源的内波假说。  相似文献   

THE SATELLITE TOWNS OF METROPOLIS GUANGZHOU：EVOLUTION， INHERENT LINKS WITH THE CENTRAL CITY AND TENDENCIES──A CASE STUDY OFRENHE TOWN     

阎小培 《中国地理科学(英文版)》1994,(1)

ＴＨＥＳＡＴＥＬＬＩＴＥＴＯＷＮＳＯＦＭＥＴＲＯＰＯＬＩＳＧＵＡＮＧＺＨＯＵ：ＥＶＯＬＵＴＩＯＮ，ＩＮＨＥＲＥＮＴＬＩＮＫＳＷＩＴＨＴＨＥＣＥＮＴＲＡＬＣＩＴＹＡＮＤＴＥＮＤＥＮＣＩＥＳ──ＡＣＡＳＥＳＴＵＤＹＯＦＲＥＮＨＥＴＯＷＮＹａｎＸｉａｏｐｅ...  相似文献   

The Qso Hosts I Zw 1 and 3C 48: Prototypes of a Merger-Driven Quasar Evolution?     

Julia Scharwächter  Andreas Eckart  Susanne Pfalzner  Jens Zuther  Melanie Krips  Eva Schinnerer  Johannes Staguhn 《Astrophysics and Space Science》2005,295(1-2):101-106

I Zw 1 and 3C 48 are two neighboring template objects at a later stage of the hypothesized merger-driven evolutionary sequence from ultra-luminous infrared galaxies (ULIRGs) to quasi-stellar objects (QSOs). Since galaxy mergers are assumed to trigger the evolution, it is important to confirm the merger properties of transitionary objects. Using multi-wavelength observations and N-body simulations, the merger histories of I Zw 1 and 3C 48 have been investigated in two separate case studies. Here, the results from both studies are compared and their relevance for the evolutionary hypothesis is discussed.This research is partly based on observations with ISAAC at the Very Large Telescope (VLT) of the European Southern Observatory (ESO) under projects 67.B-0009 and 67.B-0019.  相似文献   

Host galaxies of gamma-ray bursts and their cosmological evolution     

Stéphanie Courty  Gunnlaugur Björnsson  Einar H. Gudmundsson 《Monthly notices of the Royal Astronomical Society》2004,354(2):581-590

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Kinematics of W Ursae Majoris type binaries and evidence of the two types of formation     

S. Bilir  Y. Karata&#;  O. Demircan †  Z. Eker † 《Monthly notices of the Royal Astronomical Society》2005,357(2):497-517

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Karyological and Ecological Evolution of the Monocelididae (Platyhelminthes, Proseriata)     

M.C. Curini-Galletti  P.M. Martens 《Marine Ecology》1990,11(3):255-261

Abstract. The karyology and ecology of 76 species of Monocelididae arc discussed. Species with a basic karyotype are mainly limited to low dynamic subtidal areas: this is considered to be the ancestral habitat of the group. From there, parallel evolution resulted in colonization of more stressed environments. In all lineages, the colonization of new environments is correlated with karyotype rearrangements such as translocations and Robertsonian mechanisms of fusion and fission.  相似文献   

Environmental evolution of Gongwang Mountains during Holocene in northeastern Yunnan, China     

Wei ZHANG  Chuanchuan LI  Zhijiu CUI  Jinliang FENG 《世界地质(英文版)》2008,11(3)

This paper presents the study on two continuous glacio-lacustrine sedimentary deposits, Laotanfang (3 597 m) and Shibantang (3 689 m) located on the southern and northern sides of Hulifang peak in Yunan, China. Environmental change indexes are constructed for each deposit, based on grain size, geochemical and pollen analysis, environmental magnetic susceptibility, and 14C dating. The study of climatic environmental change since the Holocene epoch in this region shows that the climate fluctuated at different stages during the early Holocene, that is, the climate was cool and wet during 8 4-7 7 ka, cold and wet during 7 7-6 5 ka, cold and dry during 6 5-4 7 ka, cool and wet during 4 7-2 1 ka, warm and wet during 2 1-1 0 ka, and warmer and wet since 1 ka. These findings reflect the overlapping influences of the southwest and southeast monsoons in different times during the Holocene in the north part of southwestern China are in accord with other Holocene climate change models in this part of China.  相似文献