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	Figure 1: Averaged spectra observed towards the centre of L1642 (04h35m10.1s, (J2000)). The solid, dotted and dashed histograms are respectively the 12CO, 13CO and C18O profiles.
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In the text

	Figure 2: Contour maps of the 12CO line area. The square and the triangle indicate the position of IRAS 04327-1419 and IRAS 04325-1419, respectively. The two numbers given for each map are the isocontour starting values and the steps in K km s-1. The centre position (0, 0) is 04h35m30s, 28 (J2000). The arrow indicates the direction of the cloud tail seen in HI and IRAS maps.
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In the text

	Figure 3: As in Fig. 2, but for 13CO.
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In the text

	Figure 4: As in Fig. 2, but for C18O.
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In the text

	Figure 5: Result of the PMF factorization of 12CO(1-0) observations with four spectral components. The spectral profiles of the components are shown in the first frame. The other frames show the intensity distribution of the components over the observed map. The component maps are in the order of increasing radial velocity of the component.
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In the text

	Figure 6: Result of the PMF factorization of 13CO(1-0) observations with four components.
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In the text

	Figure 7: Result of the PMF factorization of C18O(1-0) observations with four components. The last component is mostly noise and is drawn with dashed line.
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In the text

	Figure 8: Observed 12CO(1-0) and 13CO(1-0) spectra (upper frames) and the residuals (lower frames) of the PMF fit at positions (0 , 9 ) and ( , 21 ). The 12CO spectra are drawn with thicker lines.
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In the text

Figure 9: The spatial distributions of the first two PMF components in the case of the 12CO(1-0) and the 13CO(1-0) observations. The blue and red contours correspond to the first and the second PMF component, respectively, as shown in Figs. 5 and 6. The contour levels are 40, 50, and 55 for the first and 20, 25, and 30 for the second 12CO component, and 14, 19, and 24 for the first and 8.5 and 11.5 for the second 13CO component. The units are the same as used in Figs. 5 and 6.

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In the text

	Figure 10: Correlation between 12CO J=2-1 and J=1-0 line areas.
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In the text

	Figure 11: W[12CO]/W[13CO] versus W[13CO].
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In the text

	Figure 12: Excitation temperature (1-0), calculated from 13CO/12CO peak antenna temperature ratio, versus radius. Error bars reflect dispersion in each distance bin.
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In the text

	Figure 13: Map of H2 column density derived from 13CO(1-0) lines assuming LTE. The contours range from  to   cm-2by   cm-2. The filled square and the triangle indicate the positions of IRAS 04237-1419 and IRAS 04325-1419.
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In the text

	Figure 14: The profile of the H2 column density derived from 13CO(1-0) observations. The dotted lines are for r-1 trends and dashed lines for r-0.2. The centre is at , (see Fig. 13).
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In the text

Figure 15: Spectra from a spherically symmetric model cloud (solid lines) and observed spectra (histograms) averaged over different annuli centred at the position 4h35m13.6s- . In the model the kinetic temperature increased linearly from 9 K in the centre to 14 K on the cloud surface. The radius of the annulus is given in each frame. Thick lines represent 13CO(1-0) and thin lines 13CO(2-1) spectra.

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In the text

Figure A.1: 12CO(1-0) channel maps. The velocity (in  km s-1) is indicated on each panel. The contour interval is 0.3 K km s-1 and the first contour is at 0.2 K km s-1.


In the text

Figure A.2: 12CO(2-1) channel maps. The velocity (in  km s-1) is indicated on each panel. The contour interval is 0.2 K km s-1 and first contour is at 0.2 K km s-1. On this figure, structures A and B, mentioned in the text, are indicated on the 0.6 km s-1 channel.


In the text

Figure A.3: 13CO(1-0) (upper) and 13CO(2-1) (lower) channel maps. The velocity (in  km s-1) is indicated on each panel. The contour interval is 0.1 K km s-1 for 1-0 and 0.05 K km s-1 for 2-1, both starting at 0.1 K km s-1.


In the text

Figure A.4: C18O(1-0) (upper) and C18O(2-1) (lower) channel maps. The velocity (in km s-1) is indicated on each panel. The contour interval is 0.03 K km s-1 for 1-0 and 0.02 K km s-1 for 2-1, the lowest contour lying at 0.1 K km s-1.


In the text

Figure A.5: Velocity diagram of 12CO(1-0) observations along the line from position (40 , ) to ( , 40 ).


In the text

Figure A.6: Eigenimages of the four first principal components calculated from the 12CO(1-0) data. Negative contours are dashed (contour spacing 0.1), greyscale represents positive values (for PC1 contour spacing is 0.05 else it is 0.2) and the full line is the zero level isocontour.


In the text

Figure A.7: Eigenvectors used to generate the eigenimages shown in Fig. A.6.


In the text

Figure B.1: Comparison of LTE column density estimates and the true, beam averaged column densities in three-dimensional model clouds with  K and volume filling factors 1.0 and 0.1. The lines indicate relations and .


In the text