All Figures

$\begin{figure} \par\includegraphics[width=8cm,clip]{1810fig1.ps}\end{figure}$ Figure 1: Spectra of the C¹⁷O (1-0) and (2-1) lines obtained towards 08563-4225 (top panels) and 15072-5855 (bottom panels). Vertical lines under the spectra indicate the hyperfine components.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7cm,clip]{1810fig2.ps}\end{figure}$ Figure 2: Examples of various morphologies of the 1.2 mm continuum emission. a) 1.2 mm continuum map of 17040-3959. Contour levels range from 0.09 ( $\sim$ $3\sigma$ ) to 0.54 by 0.09 Jy beam^-1. The cross indicates the position of the IRAS source. The solid line corresponds to the FWHM. b) Same as a) for 10123-5727. Contour levels range from 0.1 ( $\sim$ $3\sigma$ ) to 0.7 by 0.1 Jy beam^-1. c) Same as a) for 17225-3426. Contour levels range from 0.07 ( $\sim$ $3\sigma$ ) to 1.07 by 0.1 Jy beam^-1.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{1810fig3.ps}\end{figure}$ Figure 3: Histograms of some distance-independent parameters. a) angular diameters based on the SIMBA 1.2 mm continuum maps (HPBW $\simeq$ 21 $^{\prime \prime }$ ). b) Ratio between angular separation between the IRAS position and the position of the millimeter peak ( $\Delta$ ) and the source angular diameter ( $\theta$ ). c) Rotation temperatures derived from C¹⁷O line ratios. d) H₂ volume densities derived from CS line ratios.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{1810fig4.ps}\end{figure}$ Figure 4: a) Histogram of the luminosities for sources without distance ambiguity. b) Histogram of the dust temperature of the clumps, derived from grey-body fits to the SEDs.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=6.25cm,clip]{1810fig5.ps}\end{figure}$ Figure 5: SED of 16252-4853. Symbols have the meaning indicated in the top right-hand corner. The dotted line represents the best grey-body fit to points with $\lambda\geq 60~\mu$ m, obtained for dust temperature of 33 K and dust opacity index $\beta =2$ .
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.15cm,clip]{1810fig6.ps}\end{figure}$ Figure 6: Top panel: Histogram of the CS linewidths. Bottom panel: same as top panel for the C¹⁷O linewidths.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=6.15cm,clip]{1810fig7.ps}\end{figure}$ Figure 7: Plot of the linewidths of the CS (2-1) transition against the [25-12] color index. Top panel: open circles represent Low sources observed by us; filled circles indicate potential UC H II regions observed by Bronfman et al. (1996), observed with the SEST, with $\delta <-30^{\circ }$ and satisfying the criteria adopted by Palla et al. (1991): hence they are High sources. The dashed line indicates the maximum value of $\Delta v$ measured for the sources of the Sridharan/Beuther sample. Bottom panel: same as Top panel for the sources observed by Sridharan et al. (2002).
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{1810fig8.ps}\end{figure}$ Figure 8: a) Ratio between the observed full width at zero intensity ( $FWZI_{\rm obs}$ ) and that expected for a line with Gaussian shape ( $FWZI_{\rm Gauss}$ ) from Eq. (4) for the CS (2-1) (filled circles) and (3-2) (empty circles) lines versus the signal-to-noise ratio ( $T_{\rm max}/\sigma$ ) of the spectra. Significant data are those with $T_{\rm max}/\sigma >6$ (to the right of the dotted line). b) Histograms of the quantity $FWZI_{\rm obs}/FWZI_{\rm Gauss}$ for both CS (2-1) (solid line) and (3-2) (dashed line) lines. Only sources with $T_{\rm max}/\sigma >6$ are considered here.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=6.5cm,clip]{1810fig9.ps}\end{figure}$ Figure 9: Plot of the bolometric luminosity against the [25-12] color index. For sources with distance ambiguity the near value has been adopted. Top panel: open circles represent Low sources observed by us; filled circles indicate High sources observed by Bronfman et al. (1996), with $\delta <-30^{\circ }$ . The dotted line indicates the maximum value of $L_{\rm near}$ found in the Sridharan/Beuther sample. Bottom panel: same as top panel for the sources of the Sridharan/Beuther sample.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{1810fi10.ps}\end{figure}$ Figure 10: Distribution of the ratio between the NVSS radio flux and the IRAS integrated flux for High (solid line) and Low (dashed line) sources. a) Sources detected in NVSS; b) same as panel a) for sources detected also in dense gas (CS for Highs, CS or NH₃ for Lows; c) same as panel b) for sources with luminosities lower than $10^{5}~L_{\odot}$ .
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.9cm,clip]{1810fi11.ps}\end{figure}$ Figure 11: Distribution of the distance-independent quantity M/L, where M is the clump mass derived from dust emission, for our Low sources (solid line) and the High sources of the Sridharan/Beuther sample (dashed line). For both distributions, the mean value is $\sim$ $0.07~M_{\odot}/L_{\odot}$ .
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.45cm,clip]{1810fi12.ps}\end{figure}$ Figure 12: Plot of the bolometric luminosity, L, of our sources and those of the Sridharan/Beuther sample versus the gas surface density derived from dust emission, $\Sigma =M_{\rm cont}/\pi R^{2}$ . Filled circles represent our Low sources; Open triangles correspond to the Highs of the Sridharan/Beuther sample. The solid lines are theoretical curves for an accreting protostar (from top to bottom) with mass 20, 10 and 5 $M_{\odot }$ , assuming the ZAMS radius as protostellar radius. The dashed lines are the predictions obtained assuming the protostellar radius from Nakano et al. (1995).
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=6.8cm,clip]{1810fi13.ps}\end{figure}$ Figure 13: Histograms of the ratio between the virial mass $M_{\rm vir}$ and the clump masses estimated with other methods: from CS ( $M_{\rm CS}$ , solid line), from C¹⁷O ( $M_{\rm C^{17}O}$ , dashed line) and from dust emission ( $M_{\rm cont}$ , dotted line).
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1810fi14.ps}\end{figure}$ Figure 14: Plot of the average IRAS fluxes (normalised for the flux at 100 $\mu$ m, F₁₀₀) for High (solid line) and Low (dotted line) sources.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{1810fig1.ps}\end{figure}$	Figure 1: Spectra of the C¹⁷O (1-0) and (2-1) lines obtained towards 08563-4225 (top panels) and 15072-5855 (bottom panels). Vertical lines under the spectra indicate the hyperfine components.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{1810fig4.ps}\end{figure}$	Figure 4: a) Histogram of the luminosities for sources without distance ambiguity. b) Histogram of the dust temperature of the clumps, derived from grey-body fits to the SEDs.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=6.25cm,clip]{1810fig5.ps}\end{figure}$	Figure 5: SED of 16252-4853. Symbols have the meaning indicated in the top right-hand corner. The dotted line represents the best grey-body fit to points with $\lambda\geq 60~\mu$ m, obtained for dust temperature of 33 K and dust opacity index $\beta =2$ .
Open with DEXTER

$\begin{figure} \par\includegraphics[width=7.15cm,clip]{1810fig6.ps}\end{figure}$	Figure 6: Top panel: Histogram of the CS linewidths. Bottom panel: same as top panel for the C¹⁷O linewidths.
Open with DEXTER

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{1810fi10.ps}\end{figure}$	Figure 10: Distribution of the ratio between the NVSS radio flux and the IRAS integrated flux for High (solid line) and Low (dashed line) sources. a) Sources detected in NVSS; b) same as panel a) for sources detected also in dense gas (CS for Highs, CS or NH₃ for Lows; c) same as panel b) for sources with luminosities lower than $10^{5}~L_{\odot}$ .
Open with DEXTER

$\begin{figure} \par\includegraphics[width=7.9cm,clip]{1810fi11.ps}\end{figure}$	Figure 11: Distribution of the distance-independent quantity M/L, where M is the clump mass derived from dust emission, for our Low sources (solid line) and the High sources of the Sridharan/Beuther sample (dashed line). For both distributions, the mean value is $\sim$ $0.07~M_{\odot}/L_{\odot}$ .
Open with DEXTER

$\begin{figure} \par\includegraphics[width=6.8cm,clip]{1810fi13.ps}\end{figure}$	Figure 13: Histograms of the ratio between the virial mass $M_{\rm vir}$ and the clump masses estimated with other methods: from CS ( $M_{\rm CS}$ , solid line), from C¹⁷O ( $M_{\rm C^{17}O}$ , dashed line) and from dust emission ( $M_{\rm cont}$ , dotted line).
Open with DEXTER

$\begin{figure} \par\includegraphics[width=8cm,clip]{1810fi14.ps}\end{figure}$	Figure 14: Plot of the average IRAS fluxes (normalised for the flux at 100 $\mu$ m, F₁₀₀) for High (solid line) and Low (dotted line) sources.
Open with DEXTER