Dark matter heats up in dwarf galaxies
Dark matter heats up in dwarf galaxies
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DOI：
10.1093/mnras/sty3404
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发表时间：
2018-08
影响因子：
4.8
通讯作者：
J. Read;Matthew C. Walker;P. Steger
中科院分区：
文献类型：
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作者：
J. Read;Matthew C. Walker;P. Steger
由爆发性星星形成驱动的引力势波动可以在运动学上“加热”矮星系中心的暗物质。这种模型的一个关键预测是，在固定的暗物质晕质量下，恒星质量较高的矮星将具有较低的中心暗物质密度。我们利用恒星运动学和HI气体旋转曲线来推断八个矮球状和八个矮不规则星系的内部暗物质密度，这些星系具有广泛的星星形成历史。对于所有的星系，我们估计暗物质密度在一个共同的半径为150 pc，ρDM（150 pc）。我们发现，我们的样本矮星福尔斯分为两个不同的类。那些在超过6 Gyr前停止形成恒星的星系，其中心密度倾向于ρDM（150 pc）>108 M kpc−3，与冷暗物质尖点相一致，而那些形成时间更长的星星则倾向于ρDM（150 pc）<108 M kpc−3，与较浅的暗物质核心相一致。使用丰度匹配推断前的晕质量，M200，我们表明，这种二分法是在良好的协议与模型中，暗物质被加热的爆发性星星的形成。特别地，我们发现ρDM（150 pc）随着恒星质量与晕质量比M*/M200的增加而稳定地减小。我们的研究结果表明，对于主导秩序，暗物质是一种冷的，无碰撞的流体，可以在运动学上“加热”并四处移动。
Gravitational potential fluctuations driven by bursty star formation can kinematically ‘heat up’ dark matter at the centres of dwarf galaxies. A key prediction of such models is that, at a fixed dark matter halo mass, dwarfs with a higher stellar mass will have a lower central dark matter density. We use stellar kinematics and HI gas rotation curves to infer the inner dark matter densities of eight dwarf spheroidal and eight dwarf irregular galaxies with a wide range of star formation histories. For all galaxies, we estimate the dark matter density at a common radius of 150 pc, ρDM(150pc). We find that our sample of dwarfs falls into two distinct classes. Those that stopped forming stars over 6 Gyr ago favour central densities ρDM(150pc)>108 M⊙ kpc−3, consistent with cold dark matter cusps, while those with more extended star formation favour ρDM(150pc)<108 M⊙ kpc−3, consistent with shallower dark matter cores. Using abundance matching to infer pre-infall halo masses, M200, we show that this dichotomy is in excellent agreement with models in which dark matter is heated up by bursty star formation. In particular, we find that ρDM(150pc) steadily decreases with increasing stellar mass-to-halo mass ratio, M*/M200. Our results suggest that, to leading order, dark matter is a cold, collisionless, fluid that can be kinematically ‘heated up’ and moved around.