All Figures

$\begin{figure} \par\includegraphics[width=8cm]{7073_f1.eps}\end{figure}$ Figure 1: Apparent density profiles of two open clusters used for determining tidal radii. The Pleiades are shown in the top panel, NGC 129 in the bottom panel. The different colours indicate different samples of stars considered: black for $1\sigma$ -members (group (a), see text), magenta for $2\sigma$ -members (group (b)), blue for $3\sigma$ -members (group (c)), and green for " $4\sigma$ -members'' (group (d)). Vertical lines show the radii r₁ (solid) and r₂ (dashed).
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In the text

$\begin{figure} \par\includegraphics[clip,width=8cm,keepaspectratio]{7073_f2.eps}\end{figure}$ Figure 2: The general scheme of fitting cluster density profiles. Left panel: a theoretical, integrated King's profile for $r_{\rm c}=1$ pc, $r_{\rm t}=20$ pc with the fitting range $r_{\rm fit}$ and tolerance $\theta$ as indicated. Right panel: the density profiles of the open cluster Trumpler 3 from the $2\sigma$ -sample. The measured profile is shown by the short-dashed line. The empirical profile corrected for the background (see text) is indicated by crosses, the bars are Poisson errors. The vertical (blue) solid and dashed lines mark the empirical parameters r₁and r₂, respectively.
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In the text

$\begin{figure} \par\includegraphics[width=8cm]{7073_f3.eps}\end{figure}$ Figure 3: Distributions of King's radii and their relative errors for 236 open clusters. Panels a) and b) are for the core radius $r_{\rm c}$ and the tidal radius $r_{\rm t}$ measured in pc. Distributions of relative errors in core radius $\delta _{r_{\rm c}}$ and in tidal radius $\delta _{r_{\rm t}}$ are shown in panels c) and d), respectively.
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In the text

$\begin{figure} \par\includegraphics[clip,width=18cm, keepaspectratio]{7073_f4.eps}\end{figure}$ Figure 4: Examples of radial profiles from our final sample ordered by the priority of the solution. The uppermost row represents the $1\sigma$ -sample. The second row is for $2\sigma$ -solutions, the third and fourth rows illustrate $3\sigma$ and $4\sigma$ samples. The crosses show empirical data corrected for the background, the vertical bars are Poisson errors. The vertical lines indicate the derived radii. The solid lines show r₁ and $r_{\rm c}$ , the broken lines r₂ and $r_{\rm t}$ . The empirical parameters are shown with blue colour, while the fitted data are shown in red. Horizontal bars indicate the value of the rms error of the parameter. The solid curve is the fitted King profile, the broken curve (yellow) is the total profile not corrected for background.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm]{7073_f5.eps}\end{figure}$ Figure 5: Distributions of cluster masses (panel a)) and their relative rms errors(panel b)). Clusters with accurate masses( $\delta _M< 60\%$ ) are shown as the dark histogram in panel a).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,bbllx=40,bblly=84,bburx=355,bbury=685, clip= ]{7073_f6.eps}\end{figure}$ Figure 6: Comparison of tidal masses $M_{\rm c}$ of open clusters derived in the present study with literature values on counted- and MF-scaled masses as a function of the distance modulus. From top to bottom we show ratios of: counted masses of Danilov & Seleznev (1994) ( $M_{\rm D}$ to tidal masses); counted masses of Tadross et al. (2002) ( $M_{\rm T}$ to tidal masses); and the IMF-scaled masses of Lamers et al. (2005) ( $M_{\rm L}$ to tidal masses). The last panels show intercomparisons of literature data.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,bbllx=80,bblly=104,bburx=510,bbury=610,clip=]{7073_fa1.eps}\par\end{figure}$ Figure A.1: Masses and internal velocity dispersions for the open clusters: Pleiades, Praesepe, NGC 6494, NGC 2168, NGC 2682, and NGC 6705 (the clusters are ordered with distance). Upper panel: internal velocity dispersion versus distance. Dots are for proper motion dispersions, triangles for tangential velocity dispersions. Bars are rms-errors of the dispersions: bars with hats are for proper motions and bars without hats for tangential velocities (for the Pleiades and Praesepe, the symbols for the proper motion dispersions are shifted to the left for a better visibility). The line shows a linear fit to the tangential velocity dispersion data. Lower panel: cluster mass versus distance (based on literature data, see text for more detail). Crosses mark virial masses obtained from proper motion dispersions, and squares show counted masses.

In the text

$\begin{figure} \par\includegraphics[width=8cm]{7073_f3.eps}\end{figure}$	Figure 3: Distributions of King's radii and their relative errors for 236 open clusters. Panels a) and b) are for the core radius $r_{\rm c}$ and the tidal radius $r_{\rm t}$ measured in pc. Distributions of relative errors in core radius $\delta _{r_{\rm c}}$ and in tidal radius $\delta _{r_{\rm t}}$ are shown in panels c) and d), respectively.
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$\begin{figure} \par\includegraphics[width=8.5cm]{7073_f5.eps}\end{figure}$	Figure 5: Distributions of cluster masses (panel a)) and their relative rms errors(panel b)). Clusters with accurate masses( $\delta _M< 60\%$ ) are shown as the dark histogram in panel a).
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