银河系外层的螺旋结构在中
E S Levine1, Leo Blitz, Carl Heiles
1Astronomy Department, University of California, 601 Campbell Hall, Berkeley, CA 94720, USA. elevine@astron.berkeley.edu
Science (New York, N.Y.)
|June 3, 2006
概括
这项研究绘制了银河系中性的地图,揭示了一个非轴对称的,多臂螺旋结构,延伸超过25千帕秒. 这张详细的地图为我们银河系提供了新的见解.
科学领域:
- 天文学和天体物理学
- 银河系的动力学
- 星际地图学 星际地图学
背景情况:
- 银河系的大规模结构传统上被建模为轴对称,但对非轴对称特征的观测证据越来越多.
- 了解中性 (HI) 的分布和动态对于绘制螺旋臂和确定银河系盘的范围至关重要.
研究的目的:
- 为了创建一个详细的表面密度图中性在外层银河系的磁盘.
- 为了研究银河系的螺旋结构,并确定其气体盘的辐射范围.
- 描述银河系螺旋臂的特性,包括它们的形状和密度变化.
主要方法:
- 分析观测数据,绘制中性的扰动表面密度.
- 在银河系南半球的螺旋结构的识别和追踪.
- 将对数螺旋模型与观察到的螺旋臂相匹配,以确定俯仰角.
主要成果:
- 确认银河系是一个非轴对称的,多臂螺旋星系.
- 螺旋结构在外盘中清晰地划定,延伸至至少25千帕塞克,为气体盘建立最低半径.
- 中性表面密度的过密度与气体厚度降低的区域相关,沿臂的表面密度比是相对恒定的.
- 逻辑螺旋的斜角在20度和25度之间,准确地适合观察到的螺旋臂.
结论:
- 详细的HI地图提供了强有力的证据,证明银河系外盘中的非轴对称,多臂螺旋结构.
- 气体盘延伸到至少25 kiloparsecs,其结构的特点是密度变化和特定的螺旋臂几何形状.
- 这些发现完善了我们对银河系形态和螺旋星系气体分布的理解.
相关概念视频
02:42Valence Bond Theory
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:10Additional Subnuclear Structures
The eukaryotic nucleus is a double membrane-bound organelle that contains nearly all of the cell’s genetic material in the form of chromosomes. It is rightly called the “brain” of the cell as it shoulders the responsibility of responding to various physiological processes, stress, altered metabolic conditions, and other cellular signals.
The nucleus contains many membrane-less subnuclear organelles or nuclear bodies, such as nucleoli, Cajal bodies, speckles, paraspeckles, etc. These nuclear...
The nucleus contains many membrane-less subnuclear organelles or nuclear bodies, such as nucleoli, Cajal bodies, speckles, paraspeckles, etc. These nuclear...
01:19The Structure of Intermediate Filaments
The intermediate filaments are one of three widely studied cytoskeletal filaments. They are so named as their diameter (10 nm) is in between that of microfilaments (7 nm) and the microtubules (25 nm). These filaments are highly stable and can remain intact when exposed to high salt concentrations and detergents. These filaments are responsible for providing stability and mechanical support to the cells. They also help in cell adhesion and maintaining tissue integrity.
Intermediate filaments...
Intermediate filaments...
01:18Structure of Benzene: Molecular Orbital Model
According to the molecular orbital (MO) model, benzene has a planar structure with a regular hexagon of six sp2 hybridized carbons. As shown in Figure 1, each carbon is bonded to three other atoms with C–C–C and H–C–C bond angles of 120°. The C–H bond length is 109 pm, and the C–C bond length is 139 pm which is midway between the single bond length of sp3 hybridized carbons (154 pm) and sp2 hybridized carbons (133 pm).
02:10Additional Subnuclear Structures
The eukaryotic nucleus is a double membrane-bound organelle that contains nearly all of the cell’s genetic material in the form of chromosomes. It is rightly called the “brain” of the cell as it shoulders the responsibility of responding to various physiological processes, stress, altered metabolic conditions, and other cellular signals.
The nucleus contains many membrane-less subnuclear organelles or nuclear bodies, such as nucleoli, Cajal bodies, speckles, paraspeckles, etc. These nuclear...
The nucleus contains many membrane-less subnuclear organelles or nuclear bodies, such as nucleoli, Cajal bodies, speckles, paraspeckles, etc. These nuclear...