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首页> 外文期刊>The Astrophysical journal >OBSERVATIONAL ESTIMATES OF THE INITIAL POWER SPECTRUM AT SMALL SCALE FROM Lyα ABSORBERS
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OBSERVATIONAL ESTIMATES OF THE INITIAL POWER SPECTRUM AT SMALL SCALE FROM Lyα ABSORBERS

机译：Lyα吸收剂小尺度初始能谱的观测估计

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摘要

We present a new method of measuring the power spectrum of initial perturbations to an unprecedentedly small scale of ～10 h~(-1) kpc. We apply this method to a sample of 4500 Lyα absorbers and recover the cold dark matter (CDM)-like power spectrum at scales ≥300 h~(-1) kpc with a precision of ～10%. However, at scales ～10-300 h~(-1) kpc, the measured and CDM-like spectra are noticeably different. This result suggests a complex inflation with generation of excess power at small scales. The magnitude and reliability of these deviations depend upon the possible incompleteness of our sample and poorly understood process of formation of weak absorbers. Confirmation of the CDM-like shape of the initial power spectrum or detection of its distortions at small scales are equally important for widely discussed problems of physics of the early universe, galaxy formation, and reheating of the universe. We use the Zeldovich theory of gravitational instability to derive statistical description of the properties of observed structure. Our method links the observed mass function of absorbers with the correlation function of the initial velocity field and therefore avoids the Nyquist restrictions limiting the investigations based on the smoothed flux or density fields. This approach is in general consistent with numerical simulations of the process of structure formation, describes reasonably well the large-scale structure observed in the galaxy distribution at small redshifts, and emphasizes the generic similarity of galaxies and absorbers. The physical model of absorbers adopted here asserts that they are formed in the course of both linear and nonlinear adiabatic or shock compression of dark matter (DM) and gaseous matter. It allows us to link the column density and overdensity of DM and gaseous components with observed characteristics of absorbers such as the column density of neutral hydrogen, redshifts, and Doppler parameter. At scales ≥1 h~(-1) Mpc, all characteristics of the DM component, and in particular, their redshift distribution, are found to be consistent with theoretical expectations for Gaussian initial perturbations with a CDM-like power spectrum.
机译：我们提出了一种将初始扰动功率谱测量到前所未有的小规模〜10 h〜（-1）kpc的新方法。我们将该方法应用于4500个Lyα吸收剂的样品，并以≥300％〜（-1）kpc的规模恢复了类似于冷暗物质（CDM）的功率谱，精度为〜10％。但是，在〜10-300 h〜（-1）kpc的范围内，测得的光谱和类似CDM的光谱明显不同。这个结果表明，小规模的过剩发电会产生复杂的通货膨胀。这些偏差的大小和可靠性取决于我们样品的可能不完整和对弱吸收体形成过程的了解不足。对于广泛讨论的早期宇宙物理学，星系形成和宇宙再热等问题，确认初始功率谱的CDM形状或小范围变形的检测同样重要。我们使用Zeldovich重力不稳定性理论来导出对观测结构特性的统计描述。我们的方法将吸收器的观测质量函数与初始速度场的相关函数联系在一起，因此避免了奈奎斯特限制，从而限制了基于平滑通量或密度场的研究。这种方法通常与结构形成过程的数值模拟相一致，合理地描述了在小红移时在星系分布中观察到的大规模结构，并强调了星系和吸收体的一般相似性。这里采用的吸收器的物理模型断言，它们是在暗物质（DM）和气态物质的线性和非线性绝热或冲击压缩过程中形成的。它使我们能够将DM和气体组分的色谱柱密度和过密度与吸收剂的观察特性（例如中性氢的色谱柱密度，红移和多普勒参数）联系起来。在规模≥1 h〜（-1）Mpc时，发现DM分量的所有特性，特别是其红移分布，都与具有CDM一样的功率谱的高斯初始扰动的理论预期一致。

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