Astronomy & Astrophysics

All Figures

$\begin{figure} \par\includegraphics[width=16.5cm,clip]{f1.ps} \end{figure}$ Figure 1: Observed fluxes for the six stars in our sample. Filled dots and arrows show detections and 3 $\sigma$ upper limits from this paper (PdB and VLA); filled squares are interferometric data from Piétu et al. (2003; HD 34282, nearly coincident with our points) and Mannings & Sargent (1997; HD 150193 and HD 163296), respectively. Open dots are single dish JCMT data (Sylvester et al. 1996; Mannings 1994). Dashed lines show the adopted fit to the centimeter fluxes. The solid lines show the results of disk models, to which we have added the estimated free-free contribution (see text). Dotted lines show disk models that fit the single-dish fluxes (rather than the interferometric ones) at $\lambda \le 1.3$ mm. The corresponding values of $\beta$ , the opacity power-law exponent, are shown on each panel; the first value has been derived fitting our interferometric data at all wavelengths ( $\beta$ in the text and in Table 2), the second using single-dish data for $\lambda \le 1.3$ mm ( $\beta _{\rm SD}$ in the text and in Table 2). Note that for HD 163296 the models overpredict the 1.3 cm flux; this happens because we have assumed that the dust opacity is an unbroken power-law to $\lambda =3$ cm, which is likely not the case.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{f2.ps} \end{figure}$ Figure 2: Top panel: dust opacity at 1 mm as function of $a_{\rm max}$ for a size distribution $n(a)\propto a^{-q}$ between $a_{\rm min}$ = 0.01 $\mu$ m and $a_{\rm max}$ . Different curves are for different values of q, as labelled. The grains are porous conglomerates of 5% (in volume) olivine ([Fe_0.3Mg_0.7]₂SiO₄), 15% organic materials, 35% water ice and 50% vacuum; see http://www.astro.uni-jena.de/Users/dima/Opacities/RI/new_ri.html for the cross sections of the individual components. Cross sections of the porous conglomerates have been computed as in Krügel & Siebenmorgen (1994). Bottom panel: $\beta$ between 1 mm and 7 mm as function of $a_{\rm max}$ for the same grain distributions.
Open with DEXTER

In the text

$\begin{figure} \par\includegraphics[width=7.7cm,clip]{f3.ps} \end{figure}$ Figure 3: Ratio of the disk to the stellar mass as function of $M_\star$ for a large sample of pre-main-sequence stars (adapted from Natta et al. 2000). Crosses are detections, upper limits are indicated with arrows. The objects studied in this paper are marked as circles; the four resolved ones are indicated with filled circles. All the disk masses have been computed for an opacity $\kappa_{1~\rm mm}=0.01$ cm² g^-1. The dotted line corresponds to $M_{\rm d} \times(\kappa_{\rm {1~mm}}/0.01)$ / $M_\star$ = 0.3.
Open with DEXTER

In the text