Table B.1: Assumed initial abundances and cosmic-ray ionization rate for the chemical models (Figs. B.1-10).
Species Initial abundance Ref.
Initial abundances T > 100 K    
H2 1  
CO $2.0\times 10^{-4}$ a
CO2 $3.0\times 10^{-5}$ b
H2O $1.5\times 10^{-4}$ c
H2S 10-8 d
H2CO $8.0\times 10^{-8}$ d
N2 $7.0\times 10^{-5}$ e
CH4 10-7 e
C2H4 $8.0\times 10^{-8}$ e
C2H6 10-8 e
CH3OH $1.5\times 10^{-7}$ d
O 0.0 e
S 0.0 e
Initial abundances T < 100 K    
H2 1  
CO $2.0\times 10^{-4}$ d
CO2 0.0 f
H2O 0.0 f
H2S 0.0 f
N2 $7.0\times 10^{-5}$ e
CH4 10-7 e
C2H4 $8.0\times 10^{-8}$ e
C2H6 10-8 e
H2CO (60 < T(K) < 100) $8.0\times 10^{-8}$ d
H2CO (T(K) < 60) 0.0 d
CH3OH (60 < T(K) < 100) $1.5\times 10^{-7}$ d
CH3OH (T(K) < 60) 0.0 d
O 1.0-4 d
S $6.0\times 10^{-9}$ g
Cosmic-ray ionization rate $\zeta_{{\rm cr}}$ (s-1) $0.8\times 10^{-17}$ h
All abundances are relative to molecular hydrogen. a Jørgensen et al. (2002), b Boonman et al. (2003b), c Boonman & van Dishoeck (2003), d Doty et al. (2004), e Charnley (1997), f assumed to be frozen-out or absent in cold gas-phase, g Doty et al. (2002), h Stäuber et al. (2006).


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