Evolution of the luminosity function and colours of galaxies in a Λ cold dark matter universe     

K. Nagamine †  M. Fukugita  R. Cen  J.P. Ostriker 《Monthly notices of the Royal Astronomical Society》2001,327(1):L10-L14

The luminosity function of galaxies is derived from a cosmological hydrodynamic simulation of a Λ cold dark matter universe with the aid of a stellar population synthesis model. At     , the resulting B -band luminosity function has a flat faint-end slope of     with the characteristic luminosity and the normalization in fair agreement with observations, while the dark matter halo mass function is steep with a slope of     . The colour distribution of galaxies also agrees well with local observations. We also discuss the evolution of the luminosity function, and the colour distribution of galaxies from     to 5. A large evolution of the characteristic mass in the stellar mass function as a result of number evolution is compensated by luminosity evolution; the characteristic luminosity increases only by 0.8 mag from     to 2, and then declines towards higher redshift, while the B -band luminosity density continues to increase from     to 5 (but only slowly at     .  相似文献   

The re-analysis of the ROSAT data of Nova Mus 1983 using white dwarf atmosphere emission models     

&#;. Balman  J. Krautter 《Monthly notices of the Royal Astronomical Society》2001,326(4):1441-1447

The analyses of X-ray emission from classical novae during the outburst stage have shown that the soft X-ray emission below 1 keV, which is thought to originate from the photosphere of the white dwarf, is inconsistent with the simple blackbody model of emission. Thus, ROSAT Position Sensitive Proportional Counter (PSPC) archival data of the classical Nova Mus 1983 (GQ Mus) have been re-analysed in order to understand the spectral development in the X-ray wavelengths during the outburst stage. The X-ray spectra are fitted with the hot white dwarf (WD) atmosphere emission models developed for the remnants of classical novae near the Eddington luminosity. The post-outburst X-ray spectra of the remnant white dwarf are examined in the context of evolution on the Hertzsprung–Russell diagram using C–O enhanced atmosphere models. The data obtained in 1991 August (during the ROSAT All Sky Survey) indicate that the effective temperature is         . The 1992 February data show that the white dwarf had reached an effective temperature in the range         with an unabsorbed X-ray flux (i.e. ∼ bolometric flux) between     and     . We show that the H burning at the surface of the WD had most likely ceased at the time of the X-ray observations. Only the 1991 August data show evidence for ongoing H burning.  相似文献   

The intermediate-age open cluster NGC 2112     

Giovanni Carraro  Roberto Barbon  Carla S. Boschetti 《Monthly notices of the Royal Astronomical Society》2002,336(1):259-264

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Viscosity of the upper mantle from laboratory creep and anelasticity measurements in peridotite at high pressure and temperature     

Hiroki Sato 《Geophysical Journal International》1991,105(3):587-599

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Ellipsoidal collapse and an improved model for the number and spatial distribution of dark matter haloes     

Ravi K. Sheth  H. J. Mo  Giuseppe Tormen 《Monthly notices of the Royal Astronomical Society》2001,323(1):1-12

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胜利油气区有机包裹体研究及其在油气勘探中的应用     

李荣西  金奎励  廖永胜 《地球科学与环境学报》1997,(4)

应用显微光度术、显微傅立叶红外光谱（Ｍｉｃｒｏ－ＦＴ．ＩＲ）和飞行时间二次离子质谱（ＴＯＦ－ＳＩＭＳ）等原位微分析技术并结合均一温度测量对胜利油气区下第三系沙河街组沙三段中有机包裹体进行了研究。区分出两类有机包裹体，即原生有机包裹体和次生有机包裹体。结果表明两类有机包裹体特征不同，二者物质组成、有机质成分及化学结构、热演化程度等差别也较大。结合地质分析表明原生有机包裹体是沙三段烃源岩生成烃类运移产物，具“自生自储”特点，而次生有机包裹体是沙四段烃源岩生成的烃类二次运移的产物。沙三段是沙河街组油气运移和聚集的主要层位，因而是寻找油气资源的主要目标层。研究表明，有机包裹体是研究油气生成、运移、聚集和演化等成藏系统最有效的手段之一，在油气勘探中有重要的应用意义。  相似文献   

山东省黄金资源可持续开发利用     

徐金芳 《山东国土资源》2001,(Z1)

本文扼要介绍了山东省金矿地质勘查、开发现状及存在的环境问题 ,为确保山东省黄金资源可持续开发利用 ,提出要保证黄金资源的可持续供给 ,要在资源开发过程中保护好环境 ,以及要高度重视地勘单位和矿山企业自身的可持续发展等建议。  相似文献   

The Fault Block''s Framework in Boli Basin and its Control Over the Deposition     

Cao Chengrun  SHAN Xuanlong  Wang Dongpo  WANG Xianmin  Yao Ping 《世界地质(英文版)》2001,4(1)

Boli basin, between Yishu fracture belt and Dunmi fracture belt, is the biggest Mesozoic coal basin in the east of Heilongjiang Province. Now it is a fault - fold remnant basin. The basin' s shape is generally consistent with the whole distribution of the cover folds, an arc protruding southwards. The basement of the basin can be divided into three fault blocks or structural units. The formation and evoluation of the basin in Mesozoic was determined by the basement fault blocks' displacement features rusulted from by the movement of the edge faults and the main basement faults.  相似文献   

The mass of the white dwarf in the recurrent nova U Scorpii     

T.D. Thoroughgood  V.S. Dhillon  S.P. Littlefair  T.R. Marsh  D.A. Smith 《Monthly notices of the Royal Astronomical Society》2001,327(4):1323-1333

We present spectroscopy of the eclipsing recurrent nova U Sco. The radial velocity semi-amplitude of the primary star was found to be     from the motion of the wings of the He  ii λ 4686-Å emission line. By detecting weak absorption features from the secondary star, we find its radial velocity semi-amplitude to be     . From these parameters, we obtain a mass of     for the white dwarf primary star and a mass of     for the secondary star. The radius of the secondary is calculated to be     , confirming that it is evolved. The inclination of the system is calculated to be     , consistent with the deep eclipse seen in the light-curves. The helium emission lines are double-peaked, with the blueshifted regions of the disc being eclipsed prior to the redshifted regions, clearly indicating the presence of an accretion disc. The high mass of the white dwarf is consistent with the thermonuclear runaway model of recurrent nova outbursts, and confirms that U Sco is the best Type Ia supernova progenitor currently known. We predict that U Sco is likely to explode within ∼700 000 yr.  相似文献   

Scattered light models of the dust shell around HD 179821     

T.M. Gledhill  M. Takami 《Monthly notices of the Royal Astronomical Society》2001,328(1):266-276

The dust shell around the evolved star HD 179821 has been detected in scattered light in near-IR imaging polarimetry observations. Here, we subtract the contribution of the unpolarized stellar light to obtain an intrinsic linear polarization of between 30 and 40 per cent in the shell that seems to increase with radial offset from the star. The J - and K -band data are modelled using a scattering code to determine the shell parameters and dust properties. We find that the observations are well described by a spherically-symmetric distribution of dust with an r ⁻² density law, indicating that when mass-loss was occurring, the mass-loss rate was constant. The models predict that the detached nature of a spherically-symmetric, optically-thin dust shell, with a distinct inner boundary, will only be apparent in polarized flux. This is in accordance with the observations of this and other optically-thin circumstellar shells, such as IRAS 17436+5003. By fitting the shell brightness we derive an optical depth to the star that is consistent with V -band observations and that, assuming a distance of 6 kpc, gives an inner-shell radius of     , a dust number density of     at r _in and a dust mass of     . We have explored axisymmetric shell models but conclude that any deviations from spherical symmetry in the shell must be slight, with an equator-to-pole density contrast of less than 2:1. We have not been able to fit simultaneously the high linear polarizations and the small     colour excess of the shell and we attribute this to the unusual scattering properties of the dust. We suggest that the dust grains around HD 179821 either are highly elongated or consist of aggregates of smaller particles.  相似文献