All Figures

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{8036fig1.eps}\end{figure}$ Figure 1: Groups of galaxies in the sample E. Duplicate galaxies appear as an increased density of groups at the boundaries of the data releases 1 and 2.
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{8036fi2a.eps}\hspace*{4mm} \includegraphics[width=7.5cm,clip]{8036fi2b.eps}\end{figure}$ Figure 2: The virial radius - distance relation for the E and N samples ( left and right panels, respectively). Duplicate galaxies appear in the sample E as a separate population due to false pairs at very low values of the virial radius (see the band at $R_{\rm vir}\approx 10^{-4}~{\rm Mpc}~h^{-1}$ ).
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8036fig3.eps}\end{figure}$ Figure 3: The total estimated luminosities of groups as a function of distance from the observer (see Sect. 7 for details).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{8036fig4.eps}\end{figure}$ Figure 4: The number density of groups in the SDSS DR5 MAIN E and N samples (logarithmic scale) as a function of distance from the observer.
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In the text

$\begin{figure} \par\includegraphics[width=8.2cm,clip]{8036fi5a.eps}\hspace*{4mm} \includegraphics[width=8.2cm,clip]{8036fi5b.eps}\end{figure}$ Figure 5: Scaling of the group FoF linking length with redshift for the samples DR5 E ( left panel) and DR5 N ( right panel). The ordinate is the ratio of the minimal linking length LL at a redshift z necessary to keep the group together to the original linking length LL₀ that defined the group at its initial redshift z₀; the abscissa is the redshift difference $\Delta z=z-z_0$ .
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In the text

$\begin{figure} \par\includegraphics[width=7.5cm,clip]{8036fig6.eps}\end{figure}$ Figure 6: The mean ratio of radial and perpendicular sizes of groups in the sample E as a function of the initial value of the linking length for three values of the linking length ratios.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{8036fi7a.eps}\hspace*{4mm} \includegraphics[width=7.8cm,clip]{8036fi7b.eps}\end{figure}$ Figure 7: The multiplicity of groups in the samples E and N as a function of distance from the observer ( left and right panels, respectively).
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{8036fi8a.eps}\hspace*{4mm} \includegraphics[width=7.8cm,clip]{8036fi8b.eps}\end{figure}$ Figure 8: The cumulative richness distribution ( left panel) and the multiplicity function ( right panel) for the E and N samples.
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In the text

$\begin{figure} \par\includegraphics[width=7.6cm,clip]{8036fi9a.eps}\hspace*{4mm} \includegraphics[width=7.6cm,clip]{8036fi9b.eps}\end{figure}$ Figure 9: Left panel: the (maximum projected) sizes of our SDSS DR5 groups in the E sample as a function of distance. The median, and the 25% and 75% quartiles of the distribution are shown by solid lines. Right panel: the same for the rms velocities of the groups.
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In the text

$\begin{figure} \par\includegraphics[width=7.4cm,clip]{8036f10a.eps}\hspace*{4mm} \includegraphics[width=7.4cm,clip]{8036f10b.eps}\end{figure}$ Figure 10: Left panel: the (maximum projected) sizes of our SDSS DR5 groups in the N sample as a function of distance. The median, and the 25% and 75% quartiles of the distribution are shown by solid lines. Right panel: the same for the rms velocities of the groups.
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In the text

$\begin{figure} \par\includegraphics[width=8cm,clip]{8036fi11.eps}\end{figure}$ Figure 11: The luminosity weights of groups of the SDSS DR5 versus the distance from the observer.
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In the text

$\begin{figure} \par\includegraphics[width=7.8cm,clip]{8036fi12.eps}\end{figure}$ Figure 12: The number density of galaxies in the 2dF N and S samples, and in the SDSS DR5 E and N samples as a function of distance from the observer. The histograms for the 2dF are arbitrarily shifted along the ordinate for clarity.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{8036fi13.eps} \end{figure}$ Figure 13: The number of sample galaxies, groups and isolated galaxies involved in the FoF procedure versus the total number of galaxies in the releases of the SDSS and 2dF surveys. Note a well-defined proportional growth with the releases for the SDSS and a higher ``yield'' for the 2dF. These relations suggest that the FoF method has been applied homogeneously to the different releases.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{8036fi14.eps}\end{figure}$ Figure 14: Eight nearby (z < 0.04) groups ( $n \geq 2$ ) as identified in this work in a relatively sparce filament. The group members are shown with circles and four individual groups are encompassed by large circles. The field galaxies in the same redshift range are marked with small circles. For comparison, the members of the corresponding Merchán et al. (2005) groups ( $n \geq 4$ ) are marked with tilted crosses ( $\times$ ), and those of the Berlind et al. (2006) groups (the Mr18 sample, $n \geq 3$ ) are shown with crosses. Note that in Merchán et al. (2005) the rich, elongated group at left is divided into two (NE and SW) subgroups, which are nearly projected on each other along the line-of-sight.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{8036fi15.eps}\end{figure}$ Figure 15: Groups of the Berlind et al. (2006) Mr18 sample (crosses) compared to our groups in the same redshift ( 0.015 < z < 0.045) and richness ( $N_{\rm gal} \geq 3$ ) range (large circles). The pairs of galaxies ( $N_{\rm gal} = 2$ ) in our catalogue are shown with small circles.
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In the text

$\begin{figure} \par\includegraphics[width=8.5cm,clip]{8036fig1.eps}\end{figure}$	Figure 1: Groups of galaxies in the sample E. Duplicate galaxies appear as an increased density of groups at the boundaries of the data releases 1 and 2.
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$\begin{figure} \par\includegraphics[width=7.5cm,clip]{8036fi2a.eps}\hspace*{4mm} \includegraphics[width=7.5cm,clip]{8036fi2b.eps}\end{figure}$	Figure 2: The virial radius - distance relation for the E and N samples ( left and right panels, respectively). Duplicate galaxies appear in the sample E as a separate population due to false pairs at very low values of the virial radius (see the band at $R_{\rm vir}\approx 10^{-4}~{\rm Mpc}~h^{-1}$ ).
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$\begin{figure} \par\includegraphics[width=8cm,clip]{8036fig3.eps}\end{figure}$	Figure 3: The total estimated luminosities of groups as a function of distance from the observer (see Sect. 7 for details).
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{8036fig4.eps}\end{figure}$	Figure 4: The number density of groups in the SDSS DR5 MAIN E and N samples (logarithmic scale) as a function of distance from the observer.
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$\begin{figure} \par\includegraphics[width=8.2cm,clip]{8036fi5a.eps}\hspace*{4mm} \includegraphics[width=8.2cm,clip]{8036fi5b.eps}\end{figure}$	Figure 5: Scaling of the group FoF linking length with redshift for the samples DR5 E ( left panel) and DR5 N ( right panel). The ordinate is the ratio of the minimal linking length LL at a redshift z necessary to keep the group together to the original linking length LL₀ that defined the group at its initial redshift z₀; the abscissa is the redshift difference $\Delta z=z-z_0$ .
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$\begin{figure} \par\includegraphics[width=7.5cm,clip]{8036fig6.eps}\end{figure}$	Figure 6: The mean ratio of radial and perpendicular sizes of groups in the sample E as a function of the initial value of the linking length for three values of the linking length ratios.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{8036fi7a.eps}\hspace*{4mm} \includegraphics[width=7.8cm,clip]{8036fi7b.eps}\end{figure}$	Figure 7: The multiplicity of groups in the samples E and N as a function of distance from the observer ( left and right panels, respectively).
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{8036fi8a.eps}\hspace*{4mm} \includegraphics[width=7.8cm,clip]{8036fi8b.eps}\end{figure}$	Figure 8: The cumulative richness distribution ( left panel) and the multiplicity function ( right panel) for the E and N samples.
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$\begin{figure} \par\includegraphics[width=7.6cm,clip]{8036fi9a.eps}\hspace*{4mm} \includegraphics[width=7.6cm,clip]{8036fi9b.eps}\end{figure}$	Figure 9: Left panel: the (maximum projected) sizes of our SDSS DR5 groups in the E sample as a function of distance. The median, and the 25% and 75% quartiles of the distribution are shown by solid lines. Right panel: the same for the rms velocities of the groups.
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$\begin{figure} \par\includegraphics[width=7.4cm,clip]{8036f10a.eps}\hspace*{4mm} \includegraphics[width=7.4cm,clip]{8036f10b.eps}\end{figure}$	Figure 10: Left panel: the (maximum projected) sizes of our SDSS DR5 groups in the N sample as a function of distance. The median, and the 25% and 75% quartiles of the distribution are shown by solid lines. Right panel: the same for the rms velocities of the groups.
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$\begin{figure} \par\includegraphics[width=8cm,clip]{8036fi11.eps}\end{figure}$	Figure 11: The luminosity weights of groups of the SDSS DR5 versus the distance from the observer.
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$\begin{figure} \par\includegraphics[width=7.8cm,clip]{8036fi12.eps}\end{figure}$	Figure 12: The number density of galaxies in the 2dF N and S samples, and in the SDSS DR5 E and N samples as a function of distance from the observer. The histograms for the 2dF are arbitrarily shifted along the ordinate for clarity.
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{8036fi13.eps} \end{figure}$	Figure 13: The number of sample galaxies, groups and isolated galaxies involved in the FoF procedure versus the total number of galaxies in the releases of the SDSS and 2dF surveys. Note a well-defined proportional growth with the releases for the SDSS and a higher ``yield'' for the 2dF. These relations suggest that the FoF method has been applied homogeneously to the different releases.
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$\begin{figure} \par\includegraphics[width=8.5cm,clip]{8036fi15.eps}\end{figure}$	Figure 15: Groups of the Berlind et al. (2006) Mr18 sample (crosses) compared to our groups in the same redshift ( 0.015 < z < 0.045) and richness ( $N_{\rm gal} \geq 3$ ) range (large circles). The pairs of galaxies ( $N_{\rm gal} = 2$ ) in our catalogue are shown with small circles.
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