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arXiv 1405.0286astro-ph.GA
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倾斜对速度色散测量的影响及其对黑洞的意义

Effects of Inclination on Measuring Velocity Dispersion and Implications for Black Holes

Jillian Bellovary, Kelly Holley-Bockelmann, Kayhan Gültekin, Charlotte Christensen, Fabio Governato, Alyson Brooks, Sarah Loebman, Ferah Munshi

摘要:

中心黑洞质量与恒星椭球速度色散的关系(M- $σ$关系)是联系黑洞与其宿主星系的最著名和最紧密的关系之一。关于获得精确的黑洞测量值的困难,已经有很多详细的审查,这是正确的;然而,人们理所当然地认为,速度色散的测量基本上是直接的。我们研究了五个盘星系从宇宙学SPH模拟,发现由于星系方向的视线效应可以影响测量的$σ$的30%,因此黑洞质量预测高达1.0德克斯。面对的方向对应于系统较低的速度色散测量,而更多的边缘上的方向提供较高的速度色散,由于污染的磁盘恒星时,测量视线的数量。我们提醒观察者,速度弥散测量的不确定性至少为20 km/s,并且对于中等倾斜度可以大得多。这种效应可以解释局部测量的M- $σ$关系中的一些散射,特别是在低质量端。我们提供了一种方法,用于根据可观测量校正倾斜效应的观测$σ_{\rm los}$值。

英文摘要:

The relation of central black hole mass and stellar spheroid velocity dispersion (the M-$σ$ relation) is one of the best-known and tightest correlations linking black holes and their host galaxies. There has been much scrutiny concerning the difficulty of obtaining accurate black hole measurements, and rightly so; however, it has been taken for granted that measurements of velocity dispersion are essentially straightforward. We examine five disk galaxies from cosmological SPH simulations and find that line-of-sight effects due to galaxy orientation can affect the measured $σ$ by 30%, and consequently black hole mass predictions by up to 1.0 dex. Face-on orientations correspond to systematically lower velocity dispersion measurements, while more edge-on orientations give higher velocity dispersions, due to contamination by disk stars when measuring line of sight quantities. We caution observers that the uncertainty of velocity dispersion measurements is at least 20 km/s, and can be much larger for moderate inclinations. This effect may account for some of the scatter in the locally measured M-$σ$ relation, particularly at the low-mass end. We provide a method for correcting observed $σ_{\rm los}$ values for inclination effects based on observable quantities.

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