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$\begin{figure} \par\includegraphics[width=18cm,clip]{09354fig1.ps} % % \end{figure}$ Figure 1: Detected lines from the first torsionally excited state of methyl formate HCOOCH₃. The observations (histogram like curve) are compared with LTE emission models of HCOOCH₃ $\upsilon _{\rm t} = 1$ with ${\theta }_{\rm s} = 7$ $^{\prime \prime }$ , ${T_{\rm rot}} = 104$ K and $N = 9.4 \times 10^{16}$ cm^-2 (red curve) and with ${\theta }_{\rm s} = 12\hbox {$^{\prime \prime }$ }$ , ${T_{\rm rot}} = 154$ K and $N = 5.6 \times 10^{16}$ cm^-2 (green curve). The numbered lines are transitions from torsionally excited HCOOCH₃, see Table 2 for the attribution of each line.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{09354fig2.ps} % % \end{figure}$ Figure 2: Rotational diagram of the torsionally excited state of methyl formate for different source sizes. For a source size of 7 $^{\prime \prime }$ (black stars), we found a rotational temperature of ${T_{\rm rot}}$ = $104 \pm 14$ K and a column density of $N = 9.4^{+4.0}_{-2.8} \times 10^{16}$ cm^-2; for a source size of 12 $^{\prime \prime }$ (red diamonds), we found ${T_{\rm rot}} = 131 \pm 20$ K and $N = 3.4^{+1.5}_{-1.1} \times 10^{16}$ cm^-2.
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In the text

$\begin{figure} \par\includegraphics[width=8.8cm,clip]{09354fig3.ps} % % \end{figure}$ Figure 3: Rotational diagram of methyl formate in the ground state (black crosses) and methyl formate in both the ground and excited states (red stars). The source size is 12 $^{\prime \prime }$ . The rotational temperature and column density for methyl formate in the ground state are ${T_{\rm rot}} = 199 \pm 28$ K and $N = 9.6^{+0.9}_{-0.9} \times 10^{16}$ cm^-2 and ${T_{\rm rot}} = 154 \pm 8$ K and $N = 5.6^{+4.0}_{-3.7} \times 10^{16}$ cm^-2 when the ground and the first torsionally excited state are combined. For comparison, the rotational diagram for the excited state only is plotted (blue curve).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{09354fig4.ps} % % \end{figure}$ Figure 4: Rotational diagram of the ethyl cyanide in the ground state for different source sizes. For a source size of 7 $^{\prime \prime }$ (black crosses) we find a rotational temperature of ${T_{\rm rot}} = 103 \pm 9$ K and a column density of $N = 3.7^{+0.6}_{-0.5} \times 10 ^{15}$ cm^-2; for a source size of 12 $^{\prime \prime }$ (red stars) we find ${T_{\rm rot}} = 114 \pm 11$ K and $N = 1.3 \times 10^{16} \times 10^{15}$ cm^-2.
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In the text

$\begin{figure} \par\includegraphics[width=17.5cm,clip]{09354fig5.ps} % % \end{figure}$ Figure 5: Detected lines from the first two excited states $\upsilon _{\rm t} = 1$ and $\upsilon _{\rm b} = 1$ of ethyl cyanide CH₃CH₂CN. The observations (histogram like curve) were compared with LTE emission models of CH₃CH₂CN $\upsilon _{\rm t} = 1$ and $\upsilon _{\rm b} = 1$ with ${\theta }_{\rm s} = 7\hbox {$^{\prime \prime }$ }$ , T =100 K and N = 10¹⁶ cm^-2 (red curve) and T = 200 K and $N = 5 \times 10^{15}$ cm^-2 (green curve). The numbered lines are excited methyl formate lines (see Table 2). See Table 3 for the identification of the excited CH₃CH₂CN lines.
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In the text

$\begin{figure} \par\includegraphics[width=14.5cm,clip]{09354fig6.ps} % % \end{figure}$ Figure 6: Observed spectrum of W51 e2 (histogram like curve) compared with the LTE emission spectrum of methyl carbamate at different densities, for a 12 $^{\prime \prime }$ source and rotational temperature of 100 K: red curve: N = 10¹⁴ cm^-2, green curve: $N = 2 \times 10^{14}$ cm^-2, blue curve: $N = 4 \times 10^{14}$ cm^-2. The methyl carbamate lines are (from Groner et al. 2007): MC1: 14_2,13-13_1,12 (E) at 98515.38 GHz and 15_1,15-14_0,14 E and A at 98516.99 GHz; MC2: 23_1,22-22_2,21 at 155489.10 and 155492.68 GHz for the E and A symmetry, respectively and 23_2,22-22_1,21 at 155490.07 and 155493.65 GHz for the E and A symmetry, respectively; MC3 : 14_10,5-13_9,4 (A) and 14_10,4-13_9,5 (A) (blended) at 237922.60 GHz; MC4: 16_10,7-15_9,6 (A) and 16_10,6-15_9,7 (A) at 253099.30 and 253099.37 GHz, respectively.
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In the text