Challenges for Precision Cosmology with X-Ray and Sunyaev-Zeldovich Effect Gas Mass Measurements of Galaxy Clusters
Challenges for Precision Cosmology with X-Ray and Sunyaev-Zeldovich Effect Gas Mass Measurements of Galaxy Clusters
复制标题
利用 X 射线和 Sunyaev-Zeldovich 效应对星系团进行气体质量测量的精密宇宙学面临的挑战
DOI：
10.1086/505317
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
M. Norman
中科院分区：
文献类型：
--
作者：
E. Hallman;P. Motl;J. Burns;M. Norman
我们批判性地分析了星系团气体质量的测量，这是依赖于星系团气体质量分数的宇宙学研究的核心。利用数值模拟的星系团的X射线辐射和热Sunyaev-Zeldovich效应(SZE)的综合观测，我们简化了观测值以获得星系团气体质量的测量值。我们量化了与减少真实星系团观测中使用的常见简化假设相关的不确定性和系统偏差的可能来源，包括等温性和流体静力平衡。我们发现，星系团的本征变化限制了观测气体质量估计的精度，其置信度为~10%至1σ，不包括仪器效应。气体质量估计显示，令人惊讶的是，作为星团红移的函数，散布几乎没有趋势。对于完整的星系团样本，使用SZE轮廓大致为维里半径的方法是估计星系团质量的最简单、最准确和最公正的方法。如果除去合并和冷核系统，X射线方法在系统上比SZE方法更精确的质量估计器，但平均略高估了星系团气体质量(5%-10%)。我们发现样本中的冷核星团特别不适合观测质量估计，即使排除核区的辐射也是如此。星系团气体中的冷却效应改变了X射线的径向轮廓和Sze表面的亮度，即使在冷核区域之外也是如此。最后，我们发现使用通用温度分布的方法估计星团质量的精度比那些假设等温线的方法更高。
We critically analyze the measurement of galaxy cluster gas masses, which is central to cosmological studies that rely on the galaxy cluster gas mass fraction. Using synthetic observations of numerically simulated clusters viewed through their X-ray emission and thermal Sunyaev-Zeldovich effect (SZE), we reduce the observations to obtain measurements of the cluster gas mass. We quantify the possible sources of uncertainty and systematic bias associated with the common simplifying assumptions used in reducing real cluster observations, including isothermality and hydrostatic equilibrium. We find that intrinsic variations in clusters limit the precision of observational gas mass estimation to ~10% to 1 σ confidence, excluding instrumental effects. Gas mass estimates show surprisingly little trending in the scatter as a function of cluster redshift. For the full cluster sample, methods that use SZE profiles out to roughly the virial radius are the simplest, most accurate, and unbiased way to estimate cluster mass. X-ray methods are systematically more precise mass estimators than are SZE methods if merger and cool-core systems are removed, but slightly overestimate (5%-10%) the cluster gas mass on average. We find that cool-core clusters in our samples are particularly poor candidates for observational mass estimation, even when excluding emission from the core region. The effects of cooling in the cluster gas alter the radial profile of the X-ray and SZE surface brightness even outside the cool-core region. Finally, we find that methods using a universal temperature profile estimate cluster masses to higher precision than those assuming isothermality.