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Fig. 8.

image

Maps of higher moment-based non-parametric measurements for visualising the varying complexity of the Lyα profiles throughout the blob. We show maps of skewness s (left panel), kurtosis κ (centre panel), and bimodality b (right panel), as defined in Eqs. (10)–(12), respectively (see text for details). The displayed map in the left panel (middle and right panel) shows only spaxels that have a maximum S/N >  6 (maximum S/N >  13). Skewness s quantifies the asymmetry around the first central moment m1 (Eq. (5)), with s = 0 (yellow) indicating symmetric profiles, while s <  0 (shades of blue) indicate that the profile shows a larger tail towards the blue and s >  0 (shades of red) indicate that the profiles show a larger tail towards the red. Kurtosis quantifies the strength of wings (symmetric profiles) or tails (asymmetric profiles), with κ = 3 (white) indicating that the wings of the profile are comparable to a Gaussian wings, while κ >  3 (shades of purple) indicate larger tail extremity of the profiles (shades of brown), and κ <  3 indicate that there is less power in the tails compared to a Gaussian. Bimodality b is an attempt to quantify whether the profiles are double-component (b ≲ 2.6, green colours) or single-component (b ≳ 3, shown in violet) profiles (Remolina-Gutiérrez & Forero-Romero 2019). However, given the presence of noise and finite spectral resolution, a clear discriminatory power between single-component and double-component is not given by this measure in range 2.6 ≲ b ≲ 3 (light green and light violet colours). Contours and symbols are the same as in Fig. 7.

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