The first estimation of the ionization fraction in dense and translucent molecular gas across Orion B

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Table 3

Tabulated median values of the ionization fraction across different regions in Orion B: NGC 2024, NGC 2023, the Horsehead nebula, the Hummingbird filament, B9 and the Cloak.

Region	(G₀/n)_median	log₁₀ f_e
	10⁻³[cm³]	¹²CN(1−0)/N₂H⁺(1−0)	¹³CO(1−0)/HCO⁺(1−0)	C¹⁸O(1−0)/HCO⁺(1−0)
NGC 2024	227	$- 5 . 91_{- 6.02}^{- 5.81}$ $-5.91_{-6.02}^{-5.81}$	$- 6 . 74_{- 6.81}^{- 6.57}$ $-6.74_{-6.81}^{-6.57}$	$- 7 . 55_{- 7.64}^{- 7.40}$ $-7.55_{-7.64}^{-7.40}$
NGC 2023	44	$- 5 . 96_{- 6.14}^{- 5.96}$ $-5.96_{-6.14}^{-5.96}$	$- 6 . 58_{- 6.75}^{- 6.52}$ $-6.58_{-6.75}^{-6.52}$	−7.35-7.21
Hummingbird	43	$- 5 . 86_{- 5.94}^{- 5.83}$ $-5.86_{-5.94}^{-5.83}$	$- 6 . 41_{- 6.58}^{- 6.36}$ $-6.41_{-6.58}^{-6.36}$	$- 7 . 19_{- 7.38}^{- 6.93}$ $-7.19_{-7.38}^{-6.93}$
Horsehead	16	$- 5 . 99_{- 6.12}^{- 6.95}$ $-5.99_{-6.12}^{-6.95}$	$- 6 . 91_{- 6.93}^{- 6.75}$ $-6.91_{-6.93}^{-6.75}$	$- 7 . 42_{- 7.45}^{- 7.27}$ $-7.42_{-7.45}^{-7.27}$
B9	3	$- 6 . 46_{- 6.57}^{- 6.27}$ $-6.46_{-6.57}^{-6.27}$	$- 6 . 53_{- 6.64}^{- 6.41}$ $-6.53_{-6.64}^{-6.41}$	$- 7 . 14_{- 7.27}^{- 6.94}$ $-7.14_{-7.27}^{-6.94}$
Cloak	2	/	$- 6 . 49_{- 6.61}^{- 6.40}$ $-6.49_{-6.61}^{-6.40}$	$- 7 . 11_{- 7.22}^{- 6.92}$ $-7.11_{-7.22}^{-6.92}$

Notes. We show the logarithm of the ionization fraction f_e derived using intensity ratios of W(CN)/W(N₂H⁺), W(¹³CO)/W(HCO⁺), and W(C¹⁸O)/W(HCO⁺). We also tabulate percentiles (25th and 75th).

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