Impact of baryon physics on dark matter structures: a detailed simulation study of halo density profiles
Impact of baryon physics on dark matter structures: a detailed simulation study of halo density profiles
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DOI：
10.1111/j.1365-2966.2010.16613.x
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发表时间：
2010-07-11
影响因子：
4.8
通讯作者：
Booth, C. M.
中科院分区：
文献类型：
--
作者：
Duffy, Alan R.;Schaye, Joop;Booth, C. M.
重子对暗物质晕密度分布的反反应非常有趣，尤其是因为在尝试探测暗物质时，它是一个重要的系统不确定性。在这里，我们利用大量高分辨率宇宙流体动力学模拟来系统地研究这一过程及其对与星系形成相关的重子物理的依赖性。绝热收缩模型通常不能很好地描述重子对暗物质分布的影响。在维里半径的内部 10% 中，只有当我们允许模型参数随重子物理、晕质量和红移变化，从而消除所有预测能力时，模型才能成功。在更大的尺度上，仅暗物质的模拟始终比绝热收缩模型提供更好的拟合，即使我们允许后者模型的参数发生变化。如果辐射冷却有效且反馈较弱，则包含重子会导致密度分布明显更加集中。在这种情况下，暗物质晕浓度在星系（星团）尺度上可增加多达 30 (10)%。最显着的影响发生在高红移的星系中，晕中心的重子分数与总密度分布和暗物质密度分布的内斜率之间存在很强的反相关性。如果反馈很弱，就会形成等温内部轮廓，这与对大质量早期型星系的观测结果一致。然而，我们发现活动星系核（AGN）反馈，或者来自大质量恒星的极其有效的反馈，对于匹配观测到的星团和星团中的恒星分数，以及保持最大圆周速度与盘状星系观测到的维里速度相似是必要的。相对于没有反馈的情况，这些强反馈模型将星系中的重子分数减少了 3 倍。 AGN 甚至能够将星团晕和星团晕内部区域的重子分数减少 2 倍。这反过来导致内部密度分布通常比等温线浅，并且晕浓度往往低于没有重子的情况。因此，我们得出的结论是，从星系群观测推断出的浓度与达菲等人确定的模拟预测之间存在差异。并没有因包含重子而减轻。
The back-reaction of baryons on the dark matter halo density profile is of great interest, not least because it is an important systematic uncertainty when attempting to detect the dark matter. Here, we draw on a large suite of high-resolution cosmological hydrodynamical simulations to systematically investigate this process and its dependence on the baryonic physics associated with galaxy formation. The effects of baryons on the dark matter distribution are typically not well described by adiabatic contraction models. In the inner 10 per cent of the virial radius the models are only successful if we allow their parameters to vary with baryonic physics, halo mass and redshift, thereby removing all predictive power. On larger scales the profiles from dark matter only simulations consistently provide better fits than adiabatic contraction models, even when we allow the parameters of the latter models to vary. The inclusion of baryons results in significantly more concentrated density profiles if radiative cooling is efficient and feedback is weak. The dark matter halo concentration can in that case increase by as much as 30 (10) per cent on galaxy (cluster) scales. The most significant effects occur in galaxies at high redshift, where there is a strong anticorrelation between the baryon fraction in the halo centre and the inner slope of both the total and the dark matter density profiles. If feedback is weak, isothermal inner profiles form, in agreement with observations of massive, early-type galaxies. However, we find that active galactic nuclei (AGN) feedback, or extremely efficient feedback from massive stars, is necessary to match observed stellar fractions in groups and clusters, as well as to keep the maximum circular velocity similar to the virial velocity as observed for disc galaxies. These strong feedback models reduce the baryon fraction in galaxies by a factor of 3 relative to the case with no feedback. The AGN is even capable of reducing the baryon fraction by a factor of 2 in the inner region of group and cluster haloes. This in turn results in inner density profiles which are typically shallower than isothermal and the halo concentrations tend to be lower than in the absence of baryons. We therefore conclude that the disagreement between the concentrations inferred from observations of groups of galaxies and predictions from simulations that was identified by Duffy et al. is not alleviated by the inclusion of baryons.