Toward a Halo Mass Function for Precision Cosmology: The Limits of Universality
Toward a Halo Mass Function for Precision Cosmology: The Limits of Universality
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DOI：
10.1086/591439
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发表时间：
2008-03
期刊：
影响因子：
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通讯作者：
J. Tinker;A. Kravtsov;A. Klypin;K. Abazajian;Michael S. Warren;G. Yepes;S. Gottlober;D. Holz
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文献类型：
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作者：
J. Tinker;A. Kravtsov;A. Klypin;K. Abazajian;Michael S. Warren;G. Yepes;S. Gottlober;D. Holz
我们在一大套无碰撞宇宙模拟中测量了暗物质晕的质量函数，并研究了它在z≲2处的演化。晕被识别为孤立的密度峰，它们的质量是在一系列包围特定过密度的半径内测量的。我们认为，这些球状过密度质量与星系团的可观测性更直接地联系在一起，而不是用朋友之友算法(FOF)测量的质量，因此更适合于对晕丰度的准确预测。我们的模拟装置允许我们在z=0处校准1011h−1M☉⩽M⩽1015h−1M☉到≲5%范围内的维里质量函数，比以前的结果改进了2-3倍。我们推导出了在这个质量范围内的晕质量函数的拟合函数，适用于大范围的过密度，包括z=0和更早的历元。早期的研究试图校准一个通用的质量函数，即当用适当的变量表示时，相同的函数形式和参数可以用于不同的宇宙学和红移。除了我们的拟合公式外，我们的主要发现是，质量函数不能在这个水平或精度上用一个通用函数来表示。根据质量定义，“万能”函数的幅度单调地减小20%-50%，从z=0到≈=2.5.我们还在质量函数的整体形状中找到了红移演化的证据。
We measure the mass function of dark matter halos in a large set of collisionless cosmological simulations of flat ΛCDM cosmology and investigate its evolution at z≲ 2. Halos are identified as isolated density peaks, and their masses are measured within a series of radii enclosing specific overdensities. We argue that these spherical overdensity masses are more directly linked to cluster observables than masses measured using the friends-of-friends algorithm (FOF), and are therefore preferable for accurate forecasts of halo abundances. Our simulation set allows us to calibrate the mass function at z = 0 for virial masses in the range 1011 h−1 M☉ ⩽ M⩽ 1015 h−1 M☉ to ≲5%, improving on previous results by a factor of 2-3. We derive fitting functions for the halo mass function in this mass range for a wide range of overdensities, both at z = 0 and earlier epochs. Earlier studies have sought to calibrate a universal mass function, in the sense that the same functional form and parameters can be used for different cosmologies and redshifts when expressed in appropriate variables. In addition to our fitting formulae, our main finding is that the mass function cannot be represented by a universal function at this level or accuracy. The amplitude of the “universal” function decreases monotonically by ≈20%-50%, depending on the mass definition, from z = 0 to 2.5. We also find evidence for redshift evolution in the overall shape of the mass function.