**Table 9:** Beam-averaged column densities.
	NGC 7129 - FIRS 2	LkH $\alpha$ 234
Age	$\ga$ 3000 yr	$\sim$ 10⁵ yr
n(cm^-3)	$5\times 10^5$ - $3\times10 ^6$	$2\times 10^5$
Cold envelope
T_k	13 K	28 K
$\Omega_s$	$\sim$ 21 ''	$\sim$ 8''
NH₃	$4.9\times 10^{14}$	$4.0\times 10^{13}$
N₂H⁺	$3.8 \times 10^{13}$	$1.0 \times 10^{13}$
H¹³CO⁺	$2.2 \times 10^{12}$	$1.7 \times 10^{12}$
DCO⁺	$1.8 \times10^{12}$	$4.2 \times10^{11}$
N₂D⁺	$5.4 \times 10^{11}$	< $2.3 \times10^{11}$
N₂H⁺/H¹³CO⁺	17	6
NH₃/N₂H⁺	13-33^b	10
DCO⁺/H¹³CO⁺	0.7	0.2
N₂D⁺/N₂H⁺	0.014	<0.02
Warm envelope
T_k	>50 K	>100 K
$\Omega_s$	$\sim$ 9''	$\sim$ 14''
C³⁴S	$1.5 \times 10^{12}$	$1.7 \times 10^{12}$
CH₃OH	$9.8 \times 10^{14}$	$5.4 \times 10^{14}$
CH₃CN	$3.6 \times 10^{12}$	> $2.0 \times 10^{12}$
H₂CO	$7.0\times 10^{13}$	$8.0 \times 10^{13}$
H₂¹³CO	$2.3 \times 10^{12}$	$2.4 \times 10^{12}$
D₂CO	$2.0 \times 10^{12}$	$3.7 \times 10^{12}$
D₂CO/H₂CO	0.03	0.05
PDR
CN	$4.8 \times 10^{13}$	$6.1 \times 10^{13}$
HCN	$1.6 \times 10^{13}$	$2.1 \times 10^{13}$
Outflow
SiO	$2.8 \times 10^{12}$	$2.0 \times 10^{11}$

^b Assuming beam filling factor $\sim$ 1 and a source size
of 21'' for the NH₃ emitting region.

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