共查询到19条相似文献，搜索用时 281 毫秒
1.
星流在星系形成与演化过程中扮演了重要的角色,对银河系中星流的研究将有助于进一步探究银河系的合并历史.将LAMOST(Large Sky Area Multi-Object Fiber Spectroscopic Telescope)DR6光谱数据以及SDSS(Sloan Digital Sky Survey)DR12光谱数据分别与Gaia(Global Astrometric Interferometer for Astrophysics)DR2天体测量数据交叉匹配,获得恒星自行等数据.对GD-1星流在速度空间、几何空间和金属丰度上进行限制,从LAMOST DR6和SDSS DR12数据中共获得了157颗星流成员星.GD-1星流的平均金属丰度为[Fe/H]=-2.16±0.10 dex,延伸长度超过80°.收集前人给出的GD-1星流高概率成员星,组成较大的成员星样本进行对比分析,发现GD-1星流的金属丰度分布呈现内低外高的特点,沿着星流方向径向速度分布特点是两端大、中间小,?1=-20°(?1为GD-1星流坐标系横坐标)和?1=-60°附近的间隙是因为成员星运动差异形成的.根据成员星分布及其速度分布特性,推测GD-1星流起源位置是在?1=-40°附近. 相似文献
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银河系质量是描述银河系的最基本参数之一。几十年来,天文学家们估计出的银河系质量千差万别。现在,利用哈勃空间望远镜和盖亚卫星数据,更准确地估计出了银河系质量:在距离银河系中心12.9万光年的范围内的质量为1.5万亿太阳质量。 相似文献
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银晕外区存在众多星流,它们或源自银河系的矮伴星系,或源自晕族球状星团,常分别称为矮星系星流和球状星团潮汐尾。星流可以利用各类示踪星,并通过不同的途径加以探测,对若干代表性矮星系星流和球状星团潮汐尾的探测进展做了简要的介绍。 相似文献
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2003年至今,天文学家已经发现了16颗正在逃离银河系的恒星。银河系中心的黑洞可能是其背后的“元凶”。有一些恒星正在银河系中加速,它们的方向是更为广袤的星系际空间。由于它们运动的速度实在太快,银河系的引力也无法“挽留”住它们。也就是在2003年,天文学家才第一次发现了这些超高速的天体。然而几十年前理论学家就预言了它们的存在。 相似文献
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近年,在“斯必泽”空间红外望远镜的帮助之下,一个天文学家小组对银河系实施了最全面的结构分析,发现银河系属于棒状星系。令人兴奋的观测证据表明,银河系与普通的旋涡星系之间存在着巨大的差异;新的研究为银河系棒状结构的大小和指向提供了最佳的估计,这与以前的估计值相去甚远。研究表明,一条由相对年老和偏红的恒星组成的棒状结构横跨在银河系中心,大约长达2.7万光年——比此前所认为的数值长了7000光年。 相似文献
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美国的两位天文学家说,约有25000个黑洞就像围绕着中心营营飞叫的苍蝇隐藏在我们银河系的核心。 虽然,在银河系中已探知有10个恒星级黑洞候选者(见本刊1998年第4期第10页),但一些天文学家认为银河系充斥着由爆发恒星形成的黑洞,俄亥俄州立大学的米拉尔达(Jordi Miralda Escude)和古尔德(Andrew Gould)认为,这些黑洞会在银河系中心形成黑洞集团:因为这些黑洞倾向于将它们的部分轨道能量传递给在运动中不时遇到的较小的天体,丢失能量的黑洞便将向银心落去。但这种迁徙是极其缓慢的,两位科学家的计算表明:在银河系已存在的100亿年的生 相似文献
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Mapping the substructure in the Galactic halo with the next generation of astrometric satellites 总被引：1，自引：0，他引：1
Amina Helmi † P. Tim de Zeeuw 《Monthly notices of the Royal Astronomical Society》2000,319(3):657-665
We run numerical simulations of the disruption of satellite galaxies in a Galactic potential to build up the entire stellar halo, in order to investigate what the next generation of astrometric satellites will reveal by observing the halo of the Milky Way. We generate artificial DIVA , FAME and GAIA halo catalogues, in which we look for the signatures left by the accreted satellites. We develop a method based on the standard Friends-of-Friends algorithm applied to the space of integrals of motion. We find this simple method can recover about 50 per cent of the different accretion events, when the observational uncertainties expected for GAIA are taken into account, even when the exact form of the Galactic potential is unknown. The recovery rate for DIVA and FAME is much smaller, but these missions, like GAIA , should be able to test the hierarchical formation paradigm on our Galaxy by measuring the amount of halo substructure in the form of nearby kinematically cold streams with, for example, a two-point correlation function in velocity space. 相似文献
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银河系厚盘的发现，对于研究银河系以至星系的结构和演化具有重要意义。在简单回顾银河系结构研究史和厚盘发现过程的基础上，综合介绍了人们对银河系厚盘各方面性质认识的现状，并对迄今为止所提出的几种厚盘形成机制作了比较详细的说明和讨论。就目前来看，与伴星系的并合可能是形成厚盘最为可能的机制。 相似文献
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Daniel J. Rolfe Carole A. Haswell Joseph Patterson 《Monthly notices of the Royal Astronomical Society》2001,324(3):529-536
We present two simple dynamical models for Sagittarius based on N -body simulations of the progressive disruption of a satellite galaxy orbiting for 12.5 Gyr within a realistic Galactic potential. In both models the satellite initially has observable properties similar to those of current outlying dwarfs; in one case it is purely stellar while in the other it is embedded in an extended massive halo. The purely stellar progenitor is a King model with a total velocity dispersion of 18.9 km s−1 , a core radius of 0.44 kpc and a tidal radius of 3 kpc. The initial stellar distribution in the other case follows a King profile with the same core radius, a slightly larger total velocity dispersion and similar extent. Both these models are consistent with all published data on the current Sagittarius system, they match not only the observed properties of the main body of Sagittarius, but also those reported for unbound debris at larger distances. 相似文献
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简述了精确测定相对自行的方法,特别介绍了在用2～3个历元的底片和CCD观测结果推导恒星自行的过程中如何消除光学视场畸变、星等差和色差的具体办法;并介绍了用星系把相对自行推算绝对自行的方法。还介绍了用自行资料研究银河系结构和演化的一些前沿课题,其中包括星团研究、与银河系兼并的矮星系的发现、暗物质的检测、外星行星的探测和银河系中心黑洞的质量估算等。最后评价了自行在研究银河系中的重要性,论述了我国研制4m光学/近红外望远镜的重要意义。 相似文献
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Sami Dib C. Jakob Walcher Mark Heyer Edouard Audit Laurent Loinard 《Monthly notices of the Royal Astronomical Society》2009,398(3):1201-1206
Supernova (SN) explosions inject a considerable amount of energy into the interstellar medium (ISM) in regions with high-to-moderate star formation rates. In order to assess whether the driving of turbulence by supernovae is also important in the outer Galactic disc, where the star formation rates are lower, we study the spatial distribution of molecular cloud (MC) inclinations with respect to the Galactic plane. The latter contains important information on the nature of the mechanism of energy injection into the ISM. We analyse the spatial correlations between the position angles (PAs) of a selected sample of MCs (the largest clouds in the catalogue of the outer Galaxy published by Heyer et al). Our results show that when the PAs of the clouds are all mapped to values into the [0°, 90°] interval, there is a significant degree of spatial correlation between the PAs on spatial scales in the range of 100–800 pc. These scales are of the order of the sizes of individual SN shells in low-density environments such as those prevailing in the outer Galaxy and where the metallicity of the ambient gas is of the order of the solar value or smaller. These findings suggest that individual SN explosions, occurring in the outer regions of the Galaxy and in likewise spiral galaxies, albeit at lower rates, continue to play an important role in shaping the structure and dynamics of the ISM in those regions. The SN explosions we postulate here are likely associated with the existence of young stellar clusters in the far outer regions of the Galaxy and the ultraviolet emission and low levels of star formation observed with the Galaxy Evolution Explorer (GALEX) satellite in the outer regions of local galaxies. 相似文献
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Summary. Galactic globular clusters, which are ancient building blocks of our Galaxy, represent a very interesting family of stellar
systems in which some fundamental dynamical processes have taken place on time scales shorter than the age of the universe.
In contrast with galaxies, these clusters represent unique laboratories for learning about two-body relaxation, mass segregation
from equipartition of energy, stellar collisions, stellar mergers, and core collapse. In the present review, we summarize
the tremendous developments, as much theoretical as observational, that have taken place during the last two decades, and
which have led to a quantum jump in our understanding of these beautiful dynamical systems.
Received 3 August 1996 相似文献
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D. K. Ojha 《Journal of Astrophysics and Astronomy》2000,21(1-2):53-59
This paper presents an analysis of the first 2MASS (The Two Micron All Sky Survey) sampler data as observed at lower Galactic
latitude in our Galaxy. These new near-infrared data provide insight into the structure of the thin disk of our Galaxy, The
interpretation of star counts and color distributions of stars in the near-infrared with the synthetic stellar population
model, gives strong evidence that the Galactic thin disk density scale length,h
R
, is rather short (2.7 ± 0.1 kpc). 相似文献
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Liang Xi-long Zhao Jing-kun Chen Yu-qin Zhao Gang 《Chinese Astronomy and Astrophysics》2018,42(1):1-19
The stellar streams originated from the Galactic halo may be detected when they pass by the solar neighborhood, and they still keep some information at their birth times. Thus, the investigation of halo streams in the solar neighborhood is very important for understanding the formation and evolution of our Galaxy. In this paper, the researches of halo streams in the solar neighborhood are briefly reviewed. We have introduced the methods how to detect the halo streams and identify their member stars, summarized the progresses in the observation of member stars of halo streams and in the study of their origins, introduced in detail how to analyze the origins of halo streams in the solar neighborhood by means of numerical simulation and chemical abundance, and finally discussed the prospects of the LAMOST and GAIA in the research of halo streams in the solar neighborhood. 相似文献