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arXiv 2101.02525astro-ph.GA
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银河系旋转曲线中的不变性

Uncertainties in Galaxy Rotation Curves

J A Sellwood, Kristine Spekkens, Carter S. Eckel

摘要:

评估星系旋转曲线与星系形成模拟预测相匹配的可能性,需要从观测数据中得出的作为半径函数的圆周速度的不确定性在统计上是稳健的。文献中提出的不确定性很少满足这一要求。在本文中,我们提出了一个新的独立的工具,makemap,估计拟合速度在每个像素从高斯-厄米适合一个三维光谱数据立方体,连同其不确定性从修改后的引导程序。我们应用这个新的工具,中性氢光谱的18个星系的东西样本,并提出了新的速度图的不确定性。我们将速度图中的估计不确定性传播到我们之前描述的模型拟合工具中,以导出新的旋转曲线。我们从这些拟合得到的不确定性不仅考虑了观测误差,而且还考虑了拟合系统速度、旋转中心位置、星系对视线的倾斜度和强迫非圆运动的不确定性。因此,它们比以前可用的值定义得更好。我们估计的圆周速度的不确定性与以前的估计不同,其系数高达5,在某些情况下较小,在其他情况下较大。我们的结论是,良好的解决HI数据集的运动学模型的精度和可靠性有很大的不同,因此可能在他们的价值与宇宙学星系形成模拟预测的比较。

英文摘要:

Assessing the likelihood that the rotation curve of a galaxy matches predictions from galaxy formation simulations requires that the uncertainties in the circular speed as a function of radius derived from the observational data be statistically robust. Few uncertainties presented in the literature meet this requirement. In this paper we present a new standalone tool, makemap, that estimates the fitted velocity at each pixel from Gauss-Hermite fits to a 3D spectral data cube, together with its uncertainty obtained from a modified bootstrap procedure. We apply this new tool to neutral hydrogen spectra for 18 galaxies from the THINGS sample, and present new velocity maps with uncertainties. We propagate the estimated uncertainties in the velocity map into our previously-described model fitting tool DiskFit to derive new rotation curves. The uncertainties we obtain from these fits take into account not only the observational errors, but also uncertainties in the fitted systemic velocity, position of the rotation centre, inclination of the galaxy to the line of sight, and forced non-circular motion. They are therefore much better-defined than values that have previously been available. Our estimated uncertainties on the circular speeds differ from previous estimates by factors ranging up to of five, being smaller in some cases and larger in others. We conclude that kinematic models of well-resolved HI datasets vary widely in their precision and reliability, and therefore potentially in their value for comparisons with predictions from cosmological galaxy formation simulations.

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