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arXiv 0710.0589astro-ph
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现今银河系的不平衡性:来自斯隆数字巡天的结果

The Lopsidedness of Present-Day Galaxies: Results from the Sloan Digital Sky Survey

Timothy A. Reichard, Timothy M. Heckman, Gregory Rudnick, Jarle Brinchmann, Guinevere Kauffmann

摘要:

星系中恒星质量分布的大尺度不对称性被认为是发光物质和/或暗物质成分的非平衡状态的痕迹。这些可能会出现在合并,吸积和潮汐相互作用等事件的后果。这些事件是星系演化的关键。在本文中,我们量化的25155星系在z < 0.06的斯隆数字巡天数据发布4使用m = 1的方位角傅立叶模式的光分布的大尺度不平衡。我们表明,光的不平衡分布主要是由于相应的恒星质量分布的不平衡性。观测效应,如视宁度、泊松噪声和倾斜度,对于大多数样本,只会引入很小的不平衡误差。我们发现,不平衡性与其他基本的星系结构参数:低浓度,恒星质量和恒星表面质量密度的星系往往是不平衡的,而高浓度,质量和密度的星系没有。我们发现,最强的和最基本的不平衡性和其他结构参数之间的关系是与表面质量密度。我们还发现,在协议与以前的研究,偏心倾向于增加半径。这两个结果可以理解为几个因素的结果。星系和低密度星系的外部区域更容易受到潮汐扰动的影响,它们也有更长的动力学时间(因此不平衡将持续更长时间)。它们也更有可能受到暗物质晕中任何潜在的不对称性的影响。

英文摘要:

Large-scale asymmetries in the stellar mass distribution in galaxies are believed to trace non-equilibrium situations in the luminous and/or dark matter component. These may arise in the aftermath of events like mergers, accretion, and tidal interactions. These events are key in the evolution of galaxies. In this paper we quantify the large-scale lopsidedness of light distributions in 25155 galaxies at z < 0.06 from the Sloan Digital Sky Survey Data Release 4 using the m = 1 azimuthal Fourier mode. We show that the lopsided distribution of light is primarily due to a corresponding lopsidedness in the stellar mass distribution. Observational effects, such as seeing, Poisson noise, and inclination, introduce only small errors in lopsidedness for the majority of this sample. We find that lopsidedness correlates strongly with other basic galaxy structural parameters: galaxies with low concentration, stellar mass, and stellar surface mass density tend to be lopsided, while galaxies with high concentration, mass, and density are not. We find that the strongest and most fundamental relationship between lopsidedness and the other structural parameters is with the surface mass density. We also find, in agreement with previous studies, that lopsidedness tends to increase with radius. Both these results may be understood as a consequence of several factors. The outer regions of galaxies and low-density galaxies are more susceptible to tidal perturbations, and they also have longer dynamical times (so lopsidedness will last longer). They are also more likely to be affected by any underlying asymmetries in the dark matter halo.

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