共查询到19条相似文献,搜索用时 46 毫秒
1.
通过数值模拟相互作用星素(包括靶星系和入侵星系)的碰撞,研究环星系的形成。由于采用旋涡结构作为靶盘试验星分布函数,不同于Toomre采用一系列同心圆作为试验星的分布函数,模拟得到环的结构比Toomre的模拟更接近于实际环星系。 相似文献
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数值模拟表明无核环星系在10^8年,甚至时间跨度内,尽管环内的天体作小幅度的运动,但这一类星系仍然保持明显的环形结构。 相似文献
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扼要地就数值模拟在星系形成研究中的作用,数值模拟与解析模型之间的关系,数值模拟的局限性等几方面的问题作了综述,然后介绍了马普小组与日本东京大学最近的合作情况,包括合作得到的模拟样本,研究成晨和正在开展的工作。 相似文献
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用一个星系相互作用数值模拟的综合三体模型,研究椭圆星系是否由盘星系合并而成,结果表明,主要取决于星系的盘面积和星系运行轨道面的夹角,如果夹角不等于零,盘星系的相互作用是可能形成椭圆星系的,否则还是盘星系。 相似文献
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刘步林 《中国天文和天体物理学报》1994,(4)
用一个星系相互作用数值模拟的综合三体模型,研究椭圆星系是否由盘星系合并而成。结果表明,主要取决于星系的盘面和星系运行轨道面的夹角。如果夹角不等于零,盘星系的相互作用是可能形成椭圆星系的,否则还是盘星系。 相似文献
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刘步林 《中国天文和天体物理学报》1998,(3)
本文用树形法,模拟试验由一种星系相互作用模式产生椭圆星系的可能性.并用惯量张量分析方法和曲线拟合对椭球体进行结构分析,得到椭球体的半长轴相对长度. 相似文献
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Nicola Menci 《Astrophysics and Space Science》2004,294(1-2):15-22
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By means of population synthesis models with variable α/Fe ratios we derive average ages, metallicities, and [α/Fe] element
enhancements for a sample of 126 field and cluster early-type galaxies. We find a clear positive relation between [α/Fe] and
velocity dispersion. Zero-point, slope, and scatter of this correlation are the same for cluster and field galaxies. In particular,
the [α/Fe] ratios and mean ages of cluster ellipticals are positively correlated. This strongly reinforces the view that the
[α/Fe] element enhancement in ellipticals is produced by star formation timescales rather than by variations of the initial
mass function. These results indicate that the more massive the galaxy, the shorter is its star formation timescale, and the
higher is the redshift of the bulk of star formation. This finding is not compatible with the predictions from models of hierarchical
galaxy formation. The lenticular and field galaxies of the investigated sample do not follow the correlation between age and
[α/Fe], but contain a non-negligible fraction of galaxies with young average ages and high [α/Fe] ratios.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
13.
The observational investigation of the evolution of the star formation activities of early-type galaxies (ETGs) with redshifts helps us to understand the formation and evolution of this kind of galaxies. Combined with the highresolution images from HST/ACS (Hubble Space Telescope/Advanded Camera for Surveys) of the GEMS (Galaxy Evolution fromMorphology and SEDs) survey and the multi-band data from Spitzer, GALEX (Galaxy Evolution Explorer) and so on in the CDFS (Chandra Deep Field South) field, a complete sample including 456 ETGs with their redshifts in the range of 0.2 ≤ z ≤ 1.0 is selected on the basis of morphology, color and stellar mass. By using the stacking technique, the ultraviolet and infrared average luminosities of sample galaxies are measured, and the star formation rates of ETGs are estimated. The results indicate that the star formation rates of ETGs are relatively low (< 3 M yr−1) and decrease with decreasing redshifts. The mass contributed by the star formation since z = 1 is less than 15%. The analyses of stellar populations also confirm that the bulk of the population of massive ETGs was formed in the early universe (z > 2). 相似文献
14.
Using a volume-limited sample of Main Galaxies from SDSS Data Release 5,we investigate the dependence of galaxy properties on local environment.For each galaxy,a local three-dimensional density is calculated.We find that the galaxy morphological type depends strongly on the local environment:galaxies in dense environments have predominantly early type morphologies.Galaxy colors have only a weak dependence on the environment.This puts an important constraint on the process of galaxy formation. 相似文献
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Stefano Borgani 《Astrophysics and Space Science》2004,294(1-2):51-56
In my contribution I discuss the relevance that hydrodynamical simulation of clusters can play to understand the ICM physics
and to calibrate mass estimates from X-ray observable quantities. Using hydrodynamical simulations, which cover quite a large
dynamical range and include a fairly advanced treatment of the gas physics (cooling, star formation and SN feedback), I show
that scaling relations among X-ray observable quantities can be reproduced quite well. At the sametime, these simulations
fail at accounting for several observational quantities, which are related to the cooling structure of the ICM: the fraction
of stars, the temperature profiles and the gas entropy in central cluster regions. This calls for the need of introducing
in simulations suitable physical mechanisms which should regulate the cooling structure of the ICM. 相似文献
16.
Annette M.N. Ferguson 《Astrophysics and Space Science》2002,281(1-2):119-122
The far outer regions of galactic disks allow an important probe of both star formation and galaxy formation. I discuss how
observations of HII regions in these low gas density, low metallicity environments can shed light on the physical processes
which drive galactic star formation. The history of past star formation at large radii, as traced by observations of old and
intermediate-age stars, constrains the epoch at which the highest angular momentum regions of disks were in place; first results
for the M31 disk suggest this occured a significant (≳ 8 Gyr) time ago.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
17.
马駬 《中国天文和天体物理学报》1994,(2)
本文讨论了初始扰动谱中大尺度负密度扰动对星系尺度扰动峰值的局域密度的影响,以及空洞演化中边界壳层非线性发展的作用。结果表明它们并不能解释空洞的形成。但考虑星系相互作用在可见星系形成中的关键作用,把星系群与星系团的存在作为形成的必要条件时,可以用负密度扰动对星系团和星系群的局域密度的调制,解释30─60Mpc的空洞形成。对于更大尺度空洞的形成,则必须考虑对标准冷暗物质模型谱作出修正。 相似文献
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KONG Xu LIN Lin LI Jin-rong ZHOU Xu ZOU Hu LI Hong-yu CHEN Fu-zhen DU Wei FAN Zhou MAO Ye-wei WANG Jing ZHU Yi-nan ZHOU Zhi-min 《Chinese Astronomy and Astrophysics》2014
In recent years the number of worldwide 8∼10 m-class ground-based telescopes is continually increased, the 4 m-diameter or smaller telescopes have become the small and medium-sized telescopes. In order to obtain some noticeable scientific results by using these existing small and medium-sized telescopes, we have to consider very carefully what we can do, and what we can not. For this reason, the Time Allocation Committee of the 2.16 m telescope of the National Astronomical observatories of China (NAOC) has decided to support some key projects since 2013. The long-term project “Spectroscopic Observations of the Star Formation Regions in Nearby Galaxies” proposed by us is one of three key projects, it is supported by the committee with 30 dark/grey nights in each of three years. 相似文献
19.
星系中的巨分子云(GMCs)是恒星形成的主要区域,因此它的形成和演化对于星系的演化是至关重要的。本文中将介绍分子云的基本特性、分子云之间的碰撞和巨分子云的形成、碎裂和寿命以及其他环境因素,如旋臂扰动、较差自转等在巨分子云的形成和演化中的作用。同时也探讨在采用数值模拟研究巨分子云演化时所取分子云数目的影响。 相似文献