The case for a cold dark matter cusp in Draco
The case for a cold dark matter cusp in Draco
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DOI：
10.1093/mnras/sty2286
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发表时间：
2018-05
影响因子：
4.8
通讯作者：
J. Read;M. Walker;P. Steger
中科院分区：
文献类型：
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作者：
J. Read;M. Walker;P. Steger
我们使用一种新的质量建模方法——GRAVSPHERE，来测量天龙座矮球状星系的中心暗物质密度分布。天龙座的恒星形成很久以前就停止了，这使得它成为一个“原始”暗物质尖端的主要候选者，在星系形成过程中不受恒星反馈的影响。我们首先在一组被潮汐剥离的模拟“天龙人”矮人上测试GRAVSPHERE。我们表明，我们能够在95%的置信区间内正确地推断出尖端和核心模型的暗物质密度分布。虽然我们只能得到这些密度曲线的对数斜率的微弱推断，但我们能够得到内部暗物质密度在150pc， ρ _DM（150pc）时的振幅的稳健推断。我们表明，结合对更大半径密度分布的限制，这足以区分一个Λ冷暗物质（ΛCDM）顶点- ρ _DM(150 pc)≥1.8 × 10^8 M_☉kpc^{-3} -与其他具有更低内部密度的暗物质模型。然后我们将GRAVSPHERE应用于真实的Draco数据。我们发现天龙座的内部暗物质密度为ρ _DM(150 pc) = 2.4_{-0.6}^{+0.5} × 10^8 M_☉kpc^{-3}，与ΛCDM尖一致。利用一个独立于速度的SIDM模型，在ΛSIDM宇宙学模拟上校准，我们表明，天龙座的高中心密度给出了σ/m < 0.57 cm2 g-1的SIDM横截面的上界，可信度为99%。我们的结论是，像天龙座这样的附近矮星系的内部密度为暗物质模型提供了一个新的和有竞争力的探索。
We use a new mass modelling method, GRAVSPHERE, to measure the central dark matter density profile of the Draco dwarf spheroidal galaxy. Draco's star formation shut down long ago, making it a prime candidate for hosting a `pristine' dark matter cusp, unaffected by stellar feedback during galaxy formation. We first test GRAVSPHERE on a suite of tidally stripped mock `Draco'-like dwarfs. We show that we are able to correctly infer the dark matter density profile of both cusped and cored mocks within our 95 per cent confidence intervals. While we obtain only a weak inference on the logarithmic slope of these density profiles, we are able to obtain a robust inference of the amplitude of the inner dark matter density at 150 pc, ρ _DM(150 pc). We show that, combined with constraints on the density profile at larger radii, this is sufficient to distinguish a Λ Cold Dark Matter (ΛCDM) cusp - that has ρ _DM(150 pc) ≳ 1.8 × 10^8 M_☉ kpc^{-3} - from alternative dark matter models that have lower inner densities. We then apply GRAVSPHERE to the real Draco data. We find that Draco has an inner dark matter density of ρ _DM(150 pc) = 2.4_{-0.6}^{+0.5} × 10^8 M_☉ kpc^{-3}, consistent with a ΛCDM cusp. Using a velocity-independent SIDM model, calibrated on ΛSIDM cosmological simulations, we show that Draco's high central density gives an upper bound on the SIDM cross-section of σ/m < 0.57 cm2 g-1 at 99 per cent confidence. We conclude that the inner density of nearby dwarf galaxies like Draco provides a new and competitive probe of dark matter models.