HYACINTH: HYdrogen And Carbon chemistry in the INTerstellar medium in Hydro simulations

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Table A.1

Reactions in our chemical network along with the rate coefficients.

	Reaction	Type	Rate coefficient	Reference
1	C⁺ + H₂ → CH_x + H	H₂ destruction, CH_x formation	2.31 × 10⁻¹³ T^−1.3 exp(−23/T)	1,19
2	C⁺ + H₂ → C + 2H	H₂ destruction, C formation	0.99 × 10⁻¹³ T^−1.3 exp(−23/T)	1
3	$H_{3}^{+} + C \to {CH}_{x} + H_{2}$ ${\rm{H}}_3^ + + {\rm{C}} \to {\rm{C}}{{\rm{H}}_{\rm{x}}} + {{\rm{H}}_2}$	CH_x formation	1.04 × 10⁻⁹ (300/T)^0.00231 +
			$T^{- 1.5} Σ_{i = 1}^{4} c_{i} \exp (- T_{i} / T);$ ${T^{ - 1.5}}\Sigma _{i = 1}^4{c_i}\exp \left( { - {T_i}/T} \right);$
			c_i = [3.4 × 10⁻⁸, 6.97 × 10⁻⁹, 1.31 × 10⁻⁷, 1.51 × 10⁻⁴],

			T_i = [7.62, 1.38, 26.6, 8110]	2, 3
4	$H_{3}^{+} + O \to {OH}_{x} + H_{2}$ ${\rm{H}}_3^ + + {\rm{O}} \to {\rm{O}}{{\rm{H}}_{\rm{x}}} + {{\rm{H}}_2}$	OH_x formation	1.99 × 10⁹ T^−0.190	3, 4
5	CH_x + O → CO + H	CO formation	7.7 × 10⁻¹¹	1
6	OH_x + C → CO + H	CO formation	7.95 × 10⁻¹⁰ T^−0.339 exp (0.108/T)	1, 5
7	$H_{3}^{+} + e^{-} \to H_{2} + H$ ${\rm{H}}_3^ + + {{\rm{e}}^ - } \to {{\rm{H}}_2} + {\rm{H}}$	Dissociative recombination	4.54 × 10⁻⁷ × T^−0.52	11, 12
8	$H_{3}^{+} + e^{-} \to 3 H$ ${\rm{H}}_3^ + + {{\rm{e}}^ - } \to 3{\rm{H}}$	Dissociative recombination	8.46 × 10⁻⁷ × T^−0.52	11, 12
9	C⁺ + e⁻ → C + γ	Radiative recombination	$\frac{2.995 \times 10^{- 9}}{α {(1 + α)}^{1 - γ} {(1 + β)}^{1 + γ}}$ ${{2.995 \times {{10}^{ - 9}}} \over {\alpha {{(1 + \alpha )}^{1 - \gamma }}{{(1 + \beta )}^{1 + \gamma }}}}$	13,14
10	C + γ → C+ + e⁻	Photoionisation	3.5 × 10⁻¹⁰ (G₀/1.7)
			exp(−3.76 A_V) $f_{s, C} (N_{C}, N_{H_{2}})$ ${f_{s,{\rm{C}}}}\left( {{N_{\rm{C}}},{N_{{{\rm{H}}_2}}}} \right)$	6, 7
11	H₂ + γ → 2H	Photodissociation	4.2 × 10⁻¹¹ G₀
			$\exp (- 4.18 A_{V}) f_{s, H_{2}} (N_{H_{2}})$ $\exp \left( { - 4.18{A_V}} \right){f_{s,{{\rm{H}}_2}}}\left( {{N_{{{\rm{H}}_2}}}} \right)$	6, 7
12	CO + γ → C + O	Photodissociation	2.4 × 10⁻¹⁰ (G₀/1.7)
			$\exp (- 3.88 A_{V}) f_{s, CO} (N_{CO}, N_{H_{2}})$ $\exp \left( { - 3.88{A_V}} \right){f_{s,{\rm{CO}}}}\left( {{N_{{\rm{CO}}}},{N_{{{\rm{H}}_2}}}} \right)$	6, 8
13	CH_x + γ → C + H	Photodissociation	9.1 × 10⁻¹⁰ (G₀/1.7) exp (−2.12 A_V)	6
14	OH_x + γ → O + H	Photodissociation	3.8 × 10−¹⁰ (G₀/1.7) exp (−2.66 A_V)	6
15	H₂ + CR → H₂⁺ + e⁻	Cosmic-ray ionisation	2ζ_H	20
16	C + CR → C⁺ + e⁻	Cosmic-ray ionisation	3.85ζ_H	20
17	CO + CR → CO⁺ + O	Cosmic-ray ionisation	6.52ζ_H	20,22
18	C⁺ + e⁻ + grain → C	Grain-assisted recombination	$\begin{matrix} 4.558 \times 10^{- 13} [1 + 6.089 \times 10^{- 3} ψ^{1.128} \times \\ {(1 + 433.1 T^{0.04845} ψ^{- 0.8120 - 1.333 \times 10^{- 4} \ln T})]}^{- 1}; \end{matrix}$ $\matrix{ {4.558 \times {{10}^{ - 13}}\left[ {1 + 6.089 \times {{10}^{ - 3}}{\psi ^{1.128}} \times } \right.} \cr {{{\left. {\left( {1 + 433.1{T^{0.04845}}{\psi ^{ - 0.8120 - 1.333 \times {{10}^{ - 4}}\ln T}}} \right)} \right]}^{ - 1}};} \cr }$
				15
19	H + H + grain → H₂ + grain	Grain-assisted formation of H₂	3 × 10⁻¹⁷	17, 18
20	He + CR → He⁺ + e⁻	Cosmic-ray ionisation	1.1ζ_H	20,22
21	He⁺ + H₂ → H⁺ + He + H	Dissociative charge exchange	1.26 × 10⁻¹³ exp(−22.5/T)	3,27
22	${He}^{+} + H_{2} \to He + H_{2}^{+}$ ${\rm{H}}{{\rm{e}}^ + } + {{\rm{H}}_2} \to {\rm{He}} + {\rm{H}}_2^ +$	Charge exchange	7.2 × 10⁻¹⁵	25, 26
23	He⁺ + CO → He + C⁺ + O	CO destruction	1.6 × 10⁻⁹	23
24	He⁺ + e⁻ → He + γ	Radiative recombination	10⁻¹¹ T^−0.5 × [11.19 − 1.676 log₁₀ T
			−0.2852 (log₁₀T)² + 0.04433 (log₁₀T)³]	21,22
25	He⁺ + e⁻ + grain → He + γ	Grain-assisted recombination	$\begin{matrix} 5.572 \times 10^{- 14} [1 + 3.185 \times 10^{- 7} ψ^{1.512} \times \\ {(1 + 5115 T^{3.903 \times 10^{- 7}} ψ^{- 0.4956 - 5.494 \times 10^{- 7} \ln T})]}^{- 1}; \end{matrix}$ $\matrix{ {5.572 \times {{10}^{ - 14}}\left[ {1 + 3.185 \times {{10}^{ - 7}}{\psi ^{1.512}} \times } \right.} \cr {{{\left. {\left( {1 + 5115{T^{3.903 \times {{10}^{ - 7}}}}{\psi ^{ - 0.4956 - 5.494 \times {{10}^{ - 7}}\ln T}}} \right)} \right]}^{ - 1}};} \cr }$

26	$H_{3}^{+} + CO \to {HCO}^{+} + H_{2}$ ${\rm{H}}_3^ + + {\rm{CO}} \to {\rm{HC}}{{\rm{O}}^ + } + {{\rm{H}}_2}$	CO destruction, HCO⁺ formation	1.7 × 10⁻⁹	1
27	C⁺ + OH_x → HCO⁺	C⁺ destruction, HCO⁺ formation	9.15 × 10⁻¹⁰ (0.62 + 45.41 T^−1/2	1
28	HCO⁺ + e⁻ → CO + H	Dissociative recombination	1.06 × 10⁻⁵ T^−0.64	24
29	HCO⁺ + γ → CO + H⁺	Photodissociation	5.4 × 10⁻¹² (G₀/1.7) exp(−3.3 A_V)	26

Notes. The rate coefficients are in cm³ s⁻¹ for reactions 1-9, 21-24, and 26-28; in s⁻¹ for reactions 10-17, 20, and 29; in cm³ s⁻¹ ${Zd}_{- 1}$ ${\rm{Z}}_{\rm{d}}^{ - 1}$ for 18, 19, and 25, where Z_d is the dust abundance relative to the solar neighbourhood value of 0.01. ζ_H is the value of the cosmic ray ionisation rate in units of s⁻¹ H⁻¹; G₀ is the flux of the radiation field in the Habing units; A_V is the visual extinction defined in Eq. (10). In reaction $9, α = \sqrt{T / (6.67 \times 10^{- 3})}$ $\alpha = \sqrt {T/\left( {6.67 \times {{10}^{ - 3}}} \right)}$ , $β = \sqrt{T / (1.9436 \times 10^{6})}$ $\beta = \sqrt {T/\left( {1.9436 \times {{10}^6}} \right)}$ , and γ = 0.7849 + 0.1597 exp (49550/T). In reactions 18 and 25, ψ = G₀ exp(−1.87 A_V) $\sqrt{T} / (n_{e^{-}} / {cm}^{- 3})$ $\sqrt T /\left( {{n_{{{\rm{e}}^ - }}}/{\rm{c}}{{\rm{m}}^{ - 3}}} \right)$ . We note that although Heays et al. (2017) provided an updated value of the unshielded photodissociation rate for reaction 11 of 5.7 × 10⁻¹¹ (G₀/1.7), here we use the old rate from Draine & Bertoldi (1996), that is ≈ 25% lower, for a fair comparison with T15. Reactions 20-29 are only part of extended HYACINTH.

References. (1) Wakelam et al. (2012); (2) Vissapragada et al. (2016); (3) Gong et al. (2017); (4) de Ruette et al. (2016); (5) Zanchet et al. (2009); (6) Heays et al. (2017); (7) Draine & Bertoldi (1996); (8) Visser et al. (2009); (9) Glassgold & Langer (1974); (10) Liszt (2003); (11) McCall et al. (2004); (12) Woodall et al. (2007); (13) Badnell et al. (2003); (14) Badnell (2006); (15) Weingartner & Draine (2001); (16) Draine (2003); (17) Wolfire et al. (2008); (18) Hollenbach et al. (2012); (19) Anicich & Huntress (1986); (20) Le Teuff et al. (2000); (21) Hummer & Storey (1998); (22) Glover et al. (2010); (23) Kim et al. (1975); (24) Geppert et al. (2005); (25) Barlow (1984); (26) McElroy et al. (2013); (27) Schauer et al. (1989).

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