Problems, Connections and Expectations of Asteroseismology: a Summary of the Workshop     

Jørgen Christensen-Dalsgaard 《Astrophysics and Space Science》2003,284(1):277-294

The workshop took place at the beginning of what promises tobe a golden age of asteroseismology.Ground-based instrumentation is finally reaching a level of stabilitywhich allows detailed investigations of solar-like oscillations in atleast bright, slowly rotating main-sequence stars.Very extensive results are expected from the coming space missions,including data on a broad range of stars from the Eddington mission.The observational situation is therefore extremely promising.To make full use of these promises, major efforts are requiredtowards the efficient utilization of the data, through the developmentof techniques for the analysis and interpretation of the data.A broad range of topics related to these issues is discussed in the presentproceedings. Here I review some of the relevant problems,relate the asteroseismic investigations to broader areas of astrophysics and consider briefly the basis for our great expectations for the developmentof the field.  相似文献   

Chemical enrichment in the early galaxy     

Birgitta NordstrÖm 《Astrophysics and Space Science》2003,284(2):779-782

New, precise abundance data for a large number of elements in a growing sample of extremely metal-poor stars are accumulating from the new 8-m telescopes. Combined with theoretical models, these results advance our understanding of the first generations of stars, whose nucleosynthesis products are fossilised in the oldest stars we see today and thus give clues to the earliest phases of evolution in the Galaxy. In particular, the heaviest elements give us insight into the different neutron capture mechanisms and the stellar sites where such elements could be produced. They also afford an independent way to determine the age of the Galaxy, by radioactive chronology. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Photometric redshifts in the Hubble Deep Fields: evolution of extinction and the star formation rate     

Michael Rowan-Robinson 《Monthly notices of the Royal Astronomical Society》2003,345(3):819-833

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The K-band Hubble diagram of submillimetre galaxies and hyperluminous galaxies     

Stephen Serjeant  Duncan Farrah  James Geach  Toshinobu Takagi  Aprajita Verma  Ali Kaviani  Matt Fox 《Monthly notices of the Royal Astronomical Society》2003,346(4):L51-L56

We present the K -band Hubble diagrams ( K – z relations) of submillimetre-selected galaxies and hyperluminous galaxies (HLIRGs). We report the discovery of a remarkably tight K – z relation of HLIRGs, indistinguishable from that of the most luminous radio galaxies. Like radio galaxies, the HLIRG K – z relation at   z ≲ 3  is consistent with a passively evolving ∼3 L _* instantaneous starburst starting from a redshift of   z ∼ 10  . In contrast, many submillimetre-selected galaxies are ≳2 mag fainter, and the population has a much larger dispersion. We argue that dust obscuration and/or a larger mass range may be responsible for this scatter. The galaxies so far proved to be hyperluminous may have been biased towards higher AGN bolometric contributions than submillimetre-selected galaxies due to the 60-μm selection of some, so the location on the K – z relation may be related to the presence of the most massive active galactic nucleus. Alternatively, a particular host galaxy mass range may be responsible for both extreme star formation and the most massive active nuclei.  相似文献   

Direct Determination of Galaxy Luminosity Functions in Clusters     

D. Christlein  A. Zabludoff 《Astrophysics and Space Science》2003,285(1):197-201

We present R-band galaxy luminosity functions (GLFs) from aspectroscopic sample of six nearby rich galaxy clusters. In addition to individual cluster GLFs, extending to, in one case, M _R=–14, we also present composite GLFs for cluster and field galaxies toM _R=–17. All six cluster samples are consistent with the composite GLF, but there is evidence that the GLF of the quiescent population in clusters is not universal. Furthermore, the GLF of quiescent galaxies is significantly steeper in clusters than in the field. The overall GLF in clusters is consistent with that of field galaxies, except for the luminous tip, which is enhanced in clusters versus the field. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

WIYN Open Cluster Study – XVI. Optical/infrared photometry and comparisons with theoretical isochrones     

Aaron J. Grocholski  Ata Sarajedini 《Monthly notices of the Royal Astronomical Society》2003,345(3):1015-1029

We present combined optical/near-infrared photometry ( BVIK ) for six open clusters – M35, M37, NGC 1817, NGC 2477, NGC 2420 and M67. The open clusters span an age range from 150 Myr to 4 Gyr and have metal abundances from  [Fe/H]=−0.27  to +0.09 dex. We have utilized these data to test the robustness of theoretical main sequences constructed by several groups as denoted by the following designations – Padova, Baraffe, Y², Geneva and Siess. The comparisons of the models with the observations have been performed in the  [ M_V , ( B − V )₀], [ M_V , ( V − I )₀]  and  [ M_V , ( V − K )₀]  colour–magnitude diagrams as well as the distance-independent  [( V − K )₀, ( B − V )₀]  and  [( V − K )₀, ( V − I )₀]  two-colour diagrams. We conclude that none of the theoretical models reproduces the observational data in a consistent manner over the magnitude and colour range of the unevolved main sequence. In particular, there are significant zero-point and shape differences between the models and the observations. We speculate that the crux of the problem lies in the precise mismatch between theoretical and observational colour–temperature relations. These results underscore the importance of pursuing the study of stellar structure and stellar modelling with even greater intensity.  相似文献   

MULTI-DIMENSIONAL NUMERICAL STUDIES OF CONVECTION-RELATED STELLAR PROBLEMS     

Chan Kwing Lam 《紫金山天文台台刊》2003,(2)

1　IntroductionManybottlenecksinthetheoreticalstudyofstellarevolutionarisefromthelackofunder standingofsomehighlycomplicatedprocessesthatcannotbetreatedwithanalyticaltech niques .Alargeportionoftheseprocessesisrelatedtohydrodynamics,particularlyconvec tion .Theapplicationofmultidimensionalnumericalcomputationstotheinvestigationofthesedifficultproblemshasmadegreatprogressinrecentyears .Here ,weprovideasurveyoftherecentnumericalstudiesofconvectionrelatedproblems.Theobjectiveistoassistthosewhoar…  相似文献   

RETHINKING CULTURAL ADAPTATION*     

Donald L. Hardesty 《The Professional geographer》1986,38(1):11-18

Several issues surrounding the concept of cultural adaptation and its significance to cultural geography are discussed. A new model of cultural adaptation is developed to explain the evolution of spatial structures. Also a research agenda for geographic inquiry is proposed.  相似文献   

Rotation and luminosity variations in post-main sequence stars     

Paul J. Wiita 《Journal of Astrophysics and Astronomy》1981,2(4):387-403

Previous first-order analytic treatments of rotation acting upon stellar equilibria are extended to include later, post-Helium burning, stages of stellar evolution. Strong differential rotation is capable of substantially increasing the photon luminosities of post-main sequence stars, and thus accelerating their evolution. On the other hand, uniform rotation reduces the photon flux for a wide range of stellar interior types and conditions. Similar conclusions are drawn regarding the effects of rotation on the emission of neutrinos in pre-collapse phases of evolution. A brief discussion of the gravitational radiation emitted during these phases is also given.  相似文献   

信息的不可修改性与当代科学某些问题     

欧阳首承  彭涛涌 《应用地球物理》2005,2(1):56-62

本文指出了"信息确定性"所涉及的信息的不可 修改性、信息"保真性"是认识观念的重大变革。 以取消数量稳定性限制条件,得出了非线性不稳 定具有特殊性信息及其周期性,并可解释翁文波 的"可公度"法是运用了特殊性信息的特殊规律, 在物质演化问题上不能将数量的一般规律拓广至 特殊性信息中;由此涉及了当代科学没有解决物 质演化的"时间"、特殊性、非惯性系及其数量分 析伪造信息等问题。信息的客观存在性和不可修 改性,已实质上表明了将近代的"信息科学"的 信息分析等同于当代科学的数量处理是认识上的 误解。即"信息"不能等同于"数量"。  相似文献