All Figures

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fig1.eps} \end{figure}$ Figure 1: Spitzer-IRAC 8 $\mu$ m image from the GLIMPSE survey (orange) superimposed on a SuperCOSMOS H $\alpha$ image (turquoise) of RCW 79. The location of the MSX point source is indicated. The field size is $15\hbox {$^\prime $ }\times 15\hbox {$^\prime $ }$ .
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=85mm,clip]{3952fig2.eps} \end{figure}$ Figure 2: Millimetre continuum emission (contours) superimposed on a SuperCOSMOS H $\alpha$ image of the region. The first levels are 50, 100 and 150 and then increase in steps of 100 mJy/beam, from 300 to 700 mJy/beam.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fig3.eps} \end{figure}$ Figure 3: Millimetre continuum emission (contours) superimposed on the GLIMPSE 8 $\mu$ m image of the region. The levels are 100, 150 mJy/beam and then increase from 300 to 700 mJy/beam in steps of 100 mJy/beam. The condensations discussed in the text are identified by their numbers (from 1 to 9). Their limits, used for the mass derivations, are defined by the 100 mJy/beam contour (5 $\sigma$ level, see text).
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fig4.eps} \end{figure}$ Figure 4: Condensation 2 - Top: the 1.2-mm continuum emission is superimposed, in contours, on the 3.6 $\mu$ m image taken from the Spitzer GLIMPSE survey. Bottom: color composite image combining the $K_{\rm S}$ image from the 2MASS survey (in blue), and the 3.6 $\mu$ m (in green) and the 8 $\mu$ m (in red), both from the GLIMPSE survey. The stars discussed in the text are identified by their numbers in Table 3.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fig5.eps} \end{figure}$ Figure 5: As Fig. 4 but for condensation 3.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fig6.eps} \end{figure}$ Figure 6: As Fig. 4 but for condensation 4.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=85mm,clip]{3952fig7.eps} \end{figure}$ Figure 7: Magnitude-colour diagram for the sources observed towards condensations 2, 3 and 4. The thick solid curves show the main sequence (class V) and the sequence of giants (class III) for a distance of 4.3 kpc and no extinction. The thick dash-dotted curve shows the main sequence with a foreground visual extinction of 4.3 mag (see text). The two solid lines are the reddening lines for 30 mag of visual extinction for a B2V star and an M0III star. The thin dotted lines indicate the extreme values for the absolute magnitude of an O6V star with reddening lines corresponding to 30 mag of visual extinction.
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In the text

$\begin{figure} \par\includegraphics[angle=270,width=85mm,clip]{3952fig8.eps} \end{figure}$ Figure 8: Colour-colour diagram for sources observed towards condensations 2, 3 and 4. The two curves show the main sequence (class V) and the sequence of giants (class III) for a distance of 4.3 kpc and no extinction. The parallel lines are the reddening lines for 30 mag of visual extinction for a B2V star (lower) and an M0III star (upper).
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In the text

$\begin{figure} \par\includegraphics[angle=-90,width=85mm,clip]{3952fig9.eps} \end{figure}$ Figure 9: GLIMPSE colour-colour diagram, [3.6]-[4.5] versus [5.8]-[8.0], for the sources observed towards the most massive condensations detected at 1.2-mm (Nos. 2, 3 and 4) and the sources observed in the RCW 79 field (small black dots), extracted from the GLIMPSE PSC. The sources observed towards the compact H II region are identified by their numbers in Table 3 and shown as filled squares. The sources observed towards condensation 3 are shown as empty squares and identified by their numbers in Table 3 plus C3 (i.e. 1C3 for object 1 of condensation 3). Same for sources observed towards condensation 4, shown as empty triangles. The locations of Class I and II YSOs and red giants are from Allen et al. (2004) and Whitney et al. (2004). Extinction vectors are shown for $A_{\rm V}=30$ mag, taken from Allen et al. (2004). The stars discussed in the text are identified. Typical error bars are shown.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi10.eps} \end{figure}$ Figure 10: J (blue), H (green) and $K_{\rm S}$ (red) composite colour image of the cluster ionizing the compact H II region (NTT observations). The field size is $2\hbox {$.\mkern -4mu^\prime $ }66\times 3\hbox {$.\mkern -4mu^\prime $ }85$ . North is up, east is left.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi11.eps} \end{figure}$ Figure 11: NTT $K_{\rm S}$ image centred on the compact H II region. The regions and stars discussed in the text are identified.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi12.eps} \end{figure}$ Figure 12: Grey-scale image of the H $\alpha$ velocity field of RCW 79. The map is overlaid with H $\alpha$ intensity contours (in arbitrary units). The peak positions of the 1.2-mm condensations are indicated (white cross).
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi13.eps} \end{figure}$ Figure 13: Variations of $t_{\rm dyn}$ (thick curve) and $t_{\rm frag}$ (thin curves) as a function of the density, n₀, for the observed radius of 6.4 pc and three values of $a_{\rm {{S}}}$ (0.2, 0.4, and 0.6 km s^-1), respectively.
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi14.eps} \end{figure}$ Figure 14: Radius of the layer at the time of fragmentation (thin curves), $r_{\rm frag}$ , as a function of the density, n₀. The actual radius of RCW 79, 6.4 pc is shown (thick line).
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi15.eps} \end{figure}$ Figure 15: Mass of the fragments (thin curves) predicted by the model compared with the mass of the most massive observed condensation, as a function of density, n₀. The mean mass of the most massive fragment ( $\simeq$ 1000 $M_{\odot }$ ) is shown (thick line).
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In the text

$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fig1.eps} \end{figure}$	Figure 1: Spitzer-IRAC 8 $\mu$ m image from the GLIMPSE survey (orange) superimposed on a SuperCOSMOS H $\alpha$ image (turquoise) of RCW 79. The location of the MSX point source is indicated. The field size is $15\hbox {$^\prime $ }\times 15\hbox {$^\prime $ }$ .
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$\begin{figure} \par\includegraphics[angle=270,width=85mm,clip]{3952fig2.eps} \end{figure}$	Figure 2: Millimetre continuum emission (contours) superimposed on a SuperCOSMOS H $\alpha$ image of the region. The first levels are 50, 100 and 150 and then increase in steps of 100 mJy/beam, from 300 to 700 mJy/beam.
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$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fig5.eps} \end{figure}$	Figure 5: As Fig. 4 but for condensation 3.
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$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fig6.eps} \end{figure}$	Figure 6: As Fig. 4 but for condensation 4.
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$\begin{figure} \par\includegraphics[angle=270,width=85mm,clip]{3952fig8.eps} \end{figure}$	Figure 8: Colour-colour diagram for sources observed towards condensations 2, 3 and 4. The two curves show the main sequence (class V) and the sequence of giants (class III) for a distance of 4.3 kpc and no extinction. The parallel lines are the reddening lines for 30 mag of visual extinction for a B2V star (lower) and an M0III star (upper).
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$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi10.eps} \end{figure}$	Figure 10: J (blue), H (green) and $K_{\rm S}$ (red) composite colour image of the cluster ionizing the compact H II region (NTT observations). The field size is $2\hbox {$.\mkern -4mu^\prime $ }66\times 3\hbox {$.\mkern -4mu^\prime $ }85$ . North is up, east is left.
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$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi11.eps} \end{figure}$	Figure 11: NTT $K_{\rm S}$ image centred on the compact H II region. The regions and stars discussed in the text are identified.
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$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi12.eps} \end{figure}$	Figure 12: Grey-scale image of the H $\alpha$ velocity field of RCW 79. The map is overlaid with H $\alpha$ intensity contours (in arbitrary units). The peak positions of the 1.2-mm condensations are indicated (white cross).
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$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi13.eps} \end{figure}$	Figure 13: Variations of $t_{\rm dyn}$ (thick curve) and $t_{\rm frag}$ (thin curves) as a function of the density, n₀, for the observed radius of 6.4 pc and three values of $a_{\rm {{S}}}$ (0.2, 0.4, and 0.6 km s^-1), respectively.
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$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi14.eps} \end{figure}$	Figure 14: Radius of the layer at the time of fragmentation (thin curves), $r_{\rm frag}$ , as a function of the density, n₀. The actual radius of RCW 79, 6.4 pc is shown (thick line).
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$\begin{figure} \par\includegraphics[angle=0,width=85mm,clip]{3952fi15.eps} \end{figure}$	Figure 15: Mass of the fragments (thin curves) predicted by the model compared with the mass of the most massive observed condensation, as a function of density, n₀. The mean mass of the most massive fragment ( $\simeq$ 1000 $M_{\odot }$ ) is shown (thick line).
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