Surveying the Whirlpool at Arcseconds with NOEMA (SWAN) - II. Survey design and observations

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Table 5.

Typical scatter of median ¹²CO line ratios.

Line ratio	Full disk median	s_measured	s_calculated	s_physical
HCN(1−0)/CO	0.049	0.026	0.005	0.025
HNC(1−0)/CO	0.023	0.009	0.003	0.009
HCO⁺(1−0)/CO	0.036	0.013	0.004	0.013
N₂H⁺(1−0)/CO	0.014	0.006	0.003	0.006
HNCO(5−4)/CO	0.009	0.004	0.002	0.003
HNCO(4−3)/CO	0.011	0.004	0.002	0.004
C¹⁸O(1−0)/CO	0.033	0.012	0.005	0.011
¹³CO(1−0)/CO	0.121	0.039	0.011	0.038
C₂H(1−0)/CO	0.015	0.006	0.003	0.005

Notes. Median line ratios with ¹²CO(1−0) inside the full FoV calculated from pixels where both lines are detected significantly (> 3σ; see Table 4). We list their median absolute deviation to estimate the scatter (s_measured) and calculate the expected scatter based on the uncertainty maps and the median line ratio (s_calculated). The calculation of s_calculated is described in the text. Under the assumption that the measured line ratio consists of a constant line ratio with statistical noise and a physical contribution, we can estimate the scatter due to physical effects as $s_{physical} = \sqrt{s_{measured}^{2} - s_{calculated}^{2}}$ $s_{\mathrm{physical}} = \sqrt{s_{\mathrm{measured}}^2 - s_{\mathrm{calculated}}^2}$ .

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