PRIMORDIAL NON-GAUSSIANITY, SCALE-DEPENDENT BIAS, AND THE BISPECTRUM OF GALAXIES
PRIMORDIAL NON-GAUSSIANITY, SCALE-DEPENDENT BIAS, AND THE BISPECTRUM OF GALAXIES
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DOI：
10.1088/0004-637x/703/2/1230
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发表时间：
2009-04
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影响因子：
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通讯作者：
D. Jeong;E. Komatsu
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文献类型：
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作者：
D. Jeong;E. Komatsu
宇宙涨落的三点相关函数是对暴胀物理学的灵敏探测。我们使用两种不同的方法计算密度峰（例如星系）的三点函数的双谱Bg（k1, k2, k3）和傅里叶变换：matarres - lucchina - bonometto公式和星系偏置的局域性。峰的双谱不仅对底层物质密度波动敏感，而且对四点函数也很敏感。对于曲率扰动中具有物理动机的原始非高斯性的局部形式，Φ = Φ + fNLϕ2 + gNLϕ3，其中Φ是高斯场，我们表明星系双谱包含五个物理上不同的部分：(1)非线性引力演化，(2)非线性星系偏差，(3)fNL, (4) f2NL和(5)gNL。(1)、(2)和(3)的一部分在文献中已有推导，而(4)、(5)在本文中是首次推导。我们还发现，在高密度峰极限下，(3)相对于先前的压缩三角形（k1≈k2比k3）的计算得到了约15倍的增强。我们的发现表明，星系双光谱对fNL比以前认识到的更敏感，并且对一个新的术语gNL也很敏感。对于更一般形式的局部型非高斯性，系数f2NL可以解释为τNL，这允许我们使用三点和四点函数之间的关系来测试多场暴胀模型。来自高斯初始条件(1)和(2)的通常项在压缩构型中具有最小的信号，而其他项具有最大的信号；因此，我们可以很容易地区分它们。我们不能将fNL对Bg（k1, k2, k3）的影响解释为尺度相关的偏差，因此用已知的功率谱的尺度相关偏差取代星系双谱中的线性偏差会导致不正确的预测。由于原始非高斯性相对于非线性重力演化和星系偏差在高红移中的重要性增加，探测高红移宇宙的星系巡天对于探测原始非高斯性特别有用。
The three-point correlation function of cosmological fluctuations is a sensitive probe of the physics of inflation. We calculate the bispectrum, Bg(k1, k2, k3), Fourier transform of the three-point function of density peaks (e.g., galaxies), using two different methods: the Matarrese–Lucchin–Bonometto formula and the locality of galaxy bias. The bispectrum of peaks is not only sensitive to that of the underlying matter density fluctuations, but also to the four-point function. For a physically motivated, local form of primordial non-Gaussianity in the curvature perturbation, Φ = ϕ + fNLϕ2 + gNLϕ3, where ϕ is a Gaussian field, we show that the galaxy bispectrum contains five physically distinct pieces: (1) non-linear gravitational evolution, (2) non-linear galaxy bias, (3) fNL, (4) f2NL, and (5) gNL. While (1), (2), and a part of (3) have been derived in the literature, (4) and (5) are derived in this paper for the first time. We also find that, in the high-density peak limit, (3) receives an enhancement of a factor of ∼15 relative to the previous calculation for the squeezed triangles (k1 ≈ k2 ≫ k3). Our finding suggests that the galaxy bispectrum is more sensitive to fNL than previously recognized, and is also sensitive to a new term, gNL. For a more general form of local-type non-Gaussianity, the coefficient f2NL can be interpreted as τNL, which allows us to test multi-field inflation models using the relation between the three- and four-point functions. The usual terms from Gaussian initial conditions, (1) and (2), have the smallest signals in the squeezed configurations, while the others have the largest signals; thus, we can distinguish them easily. We cannot interpret the effects of fNL on Bg(k1, k2, k3) as a scale-dependent bias, and thus replacing the linear bias in the galaxy bispectrum with the scale-dependent bias known for the power spectrum results in an incorrect prediction. As the importance of primordial non-Gaussianity relative to the non-linear gravity evolution and galaxy bias increases toward higher redshifts, galaxy surveys probing a high-redshift universe are particularly useful for probing the primordial non-Gaussianity.