Measuring the escape velocity and mass profiles of galaxy clusters beyond their virial radius
Measuring the escape velocity and mass profiles of galaxy clusters beyond their virial radius
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DOI：
10.1111/j.1365-2966.2010.17946.x
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发表时间：
2010-11
影响因子：
4.8
通讯作者：
A. L. Serra;A. Diaferio;G. Murante;S. Borgani
中科院分区：
文献类型：
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作者：
A. L. Serra;A. Diaferio;G. Murante;S. Borgani
焦散技术仅使用星系红移来测量星系团到远超出维里半径的团心距离的逃逸速度和质量分布，其中动态平衡不一定成立。我们提供了这种技术的详细描述，并分析其可能的系统误差。我们将焦散技术应用于从ACDM宇宙的宇宙学流体动力学模拟中提取的质量M200 ≥ 1014 h-1 M的星系团。在星系团内每平方移动几十兆秒差距的红移下，平均而言，焦散技术可以恢复出超过10%的精度，直到r~ 4 r 200。焦散线技术也恢复了质量分布，在（0.6-4）r 200范围内的准确度超过10%，但在较小的半径上高估了质量高达70%。这种高估是忽略填充函数F β（r）的径向依赖性的结果。当半径从r~0.1r 200增加到~ 4 r 200时，单个逃逸速度剖面的1σ不确定性从~ 20%增加到~ 50%。在径向范围（0.6-4）r 200内，单个质量分布的1σ不确定度为40%-80%。当正确的维里质量已知时，在相同的径向范围内，1σ的不确定性降低到恒定的50%。我们表明，这些不确定性的幅度是完全由于球对称的假设，这是很难下降。该技术的其他潜在改进并不重要。我们的结论是，当应用于个别集群，焦散技术一般提供准确的逃逸速度和质量的配置文件，虽然在某些情况下，从真实的配置文件的偏差可以是实质性的。或者，我们可以将该技术应用于通过堆叠单个团簇获得的合成团簇：在这种情况下，逃逸速度剖面的1σ不确定性小于20%，直到4 r 200。因此，焦散线技术提供了可靠的平均轮廓，其延伸到用其他技术难以或不可能探测的区域。
The caustic technique uses galaxy redshifts alone to measure the escape velocity and mass profiles of galaxy clusters to clustrocentric distances well beyond the virial radius, where dynamical equilibrium does not necessarily hold. We provide a detailed description of this technique and analyse its possible systematic errors. We apply the caustic technique to clusters with mass M 200 ≥ 10 14 h -1 M ⊙ extracted from a cosmological hydrodynamic simulation of a ACDM universe. With a few tens of redshifts per squared comoving megaparsec within the cluster, the caustic technique, on average, recovers the profile of the escape velocity from the cluster with better than 10 per cent accuracy up to r~4r 200 . The caustic technique also recovers the mass profile with better than 10 per cent accuracy in the range (0.6-4) r 200 , but it overestimates the mass up to 70 per cent at smaller radii. This overestimate is a consequence of neglecting the radial dependence of the filling function F β (r). The 1σ uncertainty on individual escape velocity profiles increases from ~20 to ~50 per cent when the radius increases from r~0.1r 200 to ~4r 200 . Individual mass profiles have 1σ uncertainty between 40 and 80 per cent within the radial range (0.6-4)r 200 . When the correct virial mass is known, the 1σ uncertainty reduces to a constant 50 per cent on the same radial range. We show that the amplitude of these uncertainties is completely due to the assumption of spherical symmetry, which is difficult to drop. Other potential refinements of the technique are not crucial. We conclude that, when applied to individual clusters, the caustic technique generally provides accurate escape velocity and mass profiles, although, in some cases, the deviation from the real profile can be substantial. Alternatively, we can apply the technique to synthetic clusters obtained by stacking individual clusters: in this case, the 1σ uncertainty on the escape velocity profile is smaller than 20 per cent out to 4r 200 . The caustic technique thus provides reliable average profiles which extend to regions difficult or impossible to probe with other techniques.