Figure 2 (IMAGE)
Caption
Visualization of how the “different” primordial fluctuations of the universe lead to the different spatial distribution of dark matter. The central figure (common to both the upper and lower rows) shows the fluctuations in the reference Gaussian distribution. The color gradation (blue to yellow) corresponds to the value of the fluctuation at that location (low to high density regions). The left and right figures show fluctuations that deviate slightly from the Gaussian distribution, or are non-Gaussian. The sign in parentheses indicates the sign of the deviation from Gaussianity, corresponding to a negative (-) deviation on the left and a positive (+) deviation on the right. The top row is an example of isotropic non-Gaussianity. Compared to the central Gaussian fluctuation, the left figure shows an increase in large negative (dark blue) regions, while the right figure shows an increase in large positive (bright yellow) regions. It is known that we can search for such isotropic non-Gaussianity using the spatial distribution of observed galaxies. The lower panel shows an example of anisotropic non-Gaussianity. Compared to the isotropic case in the upper panel, the overall brightness and darkness is unchanged from the Gaussian fluctuation in the central panel, but the shape of each region has changed. We can search for this “anisotropic” non-Gaussianity from the spatial pattern of galaxy shapes.
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Kurita ＆ Takada
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