Dark Matter Properties and Halo Central Densities
Dark Matter Properties and Halo Central Densities
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DOI：
10.1086/340190
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发表时间：
2001-09
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影响因子：
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通讯作者：
S. M. Khairul Alam;J. Bullock;David H. Weinberg
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文献类型：
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作者：
S. M. Khairul Alam;J. Bullock;David H. Weinberg
利用一个经过数值模拟校准的解析模型，计算了具有宇宙学常数的“常规”冷暗物质模型(LCDM)和具有略微修改的参数的“倾斜”模型(TLCDM)中暗物质晕的中心密度，这两个模型是由最近对Lyα森林数据的分析引起的。我们还计算了热暗物质(WDM)如何通过延迟晕的形成和施加相空间约束来修正这些预测的密度。作为中心密度的一种度量，我们采用了ΔV/2量，这是以临界密度为单位的晕旋转曲线在半径RV/2内下降到其最大值的一半的密度。我们将理论预测与从暗物质占主导地位的盘状星系的自转曲线估计的ΔV/2值进行了比较。假设暗晕由Navarro-Frenk-White轮廓描述，我们的结果表明，传统的LCDM模型预测了过高的暗物质密度，除非数据中存在对晕分布的低浓度尾部的一些选择偏差。粒子质量为0.5-1keV的WDM模式与观测数据吻合较好。然而，修改后的冷暗物质模型TLCDM同样符合数据，这表明解决“晕核”问题的方法可能在于适度改变宇宙学参数，而不是彻底改变暗物质的性质。如果冷暗物质晕具有摩尔等人发现的更陡峭的密度分布，那么传统的LCDM和TLCDM都不能重现观测到的中心密度。
Using an analytic model calibrated against numerical simulations, we calculate the central densities of dark matter halos in a "conventional" cold dark matter model with a cosmological constant (LCDM) and in a "tilted" model (TLCDM) with slightly modified parameters motivated by recent analyses of Lyα forest data. We also calculate how warm dark matter (WDM) would modify these predicted densities by delaying halo formation and imposing phase-space constraints. As a measure of central density, we adopt the quantity ΔV/2, the density within the radius RV/2 at which the halo rotation curve falls to half of its maximum value, in units of the critical density. We compare the theoretical predictions to values of ΔV/2 estimated from the rotation curves of dark matter-dominated disk galaxies. Assuming that dark halos are described by Navarro-Frenk-White profiles, our results suggest that the conventional LCDM model predicts excessively high dark matter densities, unless there is some selection bias in the data toward the low-concentration tail of the halo distribution. A WDM model with particle mass 0.5-1 keV provides a better match to the observational data. However, the modified cold dark matter model, TLCDM, fits the data equally well, suggesting that the solution to the "halo cores" problem might lie in moderate changes to cosmological parameters rather than radical changes to the properties of dark matter. If cold dark matter halos have the steeper density profiles found by Moore et al., then neither conventional LCDM nor TLCDM can reproduce the observed central densities.