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arXiv 1202.1284astro-ph.COastro-ph.GA
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小尺度原始功率谱的新探索:超紧微晕的天体测量微透镜

A new probe of the small-scale primordial power spectrum: astrometric microlensing by ultracompact minihalos

Fangda Li, Adrienne L. Erickcek, Nicholas M. Law

摘要:

暗物质被包裹在初始振幅较大的密度扰动中(δ-rho/rho > 1 e-3),在重组后不久坍缩,形成超紧微晕(UCMH)。它们的高中心密度使UCMH特别适合通过天体测量微透镜进行探测:当UCMH移动时,它会改变背景恒星的视位置。质量大于几个太阳质量的UCMH可以产生独特的天体测量微透镜信号,可以被空间天体测量任务盖亚探测到。如果盖亚没有检测到任何UCMH的引力透镜,那么它就建立了它们丰度的上限,并限制了k~2700 Mpc^{-1}的原始功率谱的振幅。这些限制补充的上限的原始功率谱的振幅来自UCMH的伽玛射线发射的限制,因为天体测量微透镜信号产生的UCMH是最大化,如果暗物质湮灭率太低,影响UCMH的密度分布。如果UCMH中的暗物质湮灭是不可探测的,那么盖亚对UCMH的搜索可能会将原初功率谱的振幅限制在1 e-5以下;这个界限比不存在原初黑洞的界限强三个数量级。

英文摘要:

The dark matter enclosed in a density perturbation with a large initial amplitude (delta-rho/rho > 1e-3) collapses shortly after recombination and forms an ultracompact minihalo (UCMH). Their high central densities make UCMHs especially suitable for detection via astrometric microlensing: as the UCMH moves, it changes the apparent position of background stars. A UCMH with a mass larger than a few solar masses can produce a distinctive astrometric microlensing signal that is detectable by the space astrometry mission Gaia. If Gaia does not detect gravitational lensing by any UCMHs, then it establishes an upper limit on their abundance and constrains the amplitude of the primordial power spectrum for k~2700 Mpc^{-1}. These constraints complement the upper bound on the amplitude of the primordial power spectrum derived from limits on gamma-ray emission from UCMHs because the astrometric microlensing signal produced by an UCMH is maximized if the dark-matter annihilation rate is too low to affect the UCMH's density profile. If dark matter annihilation within UCMHs is not detectable, a search for UCMHs by Gaia could constrain the amplitude of the primordial power spectrum to be less than 1e-5; this bound is three orders of magnitude stronger than the bound derived from the absence of primordial black holes.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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