扁平色散支持星系的质量估算
Mass estimators for flattened dispersion-supported galaxies
摘要：
我们研究了基于可观测速度色散和半光半径$R_\mathrm{h}$的色散支持星系质量估计的可靠性。我们展示了如何将它们扩展到扁平系统，并在假设暗物质密度和恒星密度在相同的自相似椭球上分层的情况下，提供了椭球内质量的简单公式。我们明确地证明了球形质量估计值（Walker等人，2009年，Wolf等人，2010年）给出了半光椭球内质量的准确值，前提是$R_\mathrm{h}$被其“圆形”类似物$R_\mathrm{h}\sqrt{1-ε}$取代。我们提供了一个数学的理由，这个令人惊讶的简单和有效的解决方案。这意味着，例如，质光比不仅在光和暗物质呈球形分布时有效，而且在它们在具有相同恒定形状的椭球体上变平时也有效。
英文摘要：
We investigate the reliability of mass estimators based on the observable velocity dispersion and half-light radius $R_\mathrm{h}$ for dispersion-supported galaxies. We show how to extend them to flattened systems and provide simple formulae for the mass within an ellipsoid under the assumption the dark matter density and the stellar density are stratified on the same self-similar ellipsoids. We demonstrate explicitly that the spherical mass estimators (Walker et al. 2009, Wolf et al. 2010) give accurate values for the mass within the half-light ellipsoid, provided $R_\mathrm{h}$ is replaced by its `circularized' analogue $R_\mathrm{h}\sqrt{1-ε}$. We provide a mathematical justification for this surprisingly simple and effective workaround. It means, for example, that the mass-to-light ratios are valid not just when the light and dark matter are spherically distributed, but also when they are flattened on ellipsoids of the same constant shape.
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