Upper limits to interstellar NH+ and para-NH2− abundances - Herschel-HIFI observations towards Sgr B2 (M) and G10.6−0.4 (W31C)

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Table 3

Chemical models.

Model	A _V	n _H ^a	T _K	T _dust	ζ(H₂) ^b	Metallicity^c
	(mag)	(cm^-3)	(K)	(K)	(s^-1)

Diffuse^d	0.5	70	100	17	2 × 10^-16	High
Translucent^d	3	5 × 10³	30 & 50	10	1.3 × 10^-17	Low
Dense^d	10	2 × 10⁴	10 & 30	10	1.3 × 10^-17	Low
Sgr B2 (M) envelope^e	300	4 × 10³	40	10	4× 10^-16	High

Notes. All models use a ultraviolet flux of 1 G₀.

^(a)

The total hydrogen density n_H = 2n(H₂) + n(H).

^(b)

The cosmic ionisation rate of molecular hydrogen (cf. Indriolo et al. 2012).

^(c)

The assumed initial metal abundances are found in Table D.5.

^(d)

Typical conditions in respective cloud type (e.g. Snow & McCall 2006).

^(e)

Lis & Goldsmith (1989), van der Tak et al. (2006) and Ott et al. (2014).

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