Astronomy & Astrophysics

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$\begin{figure} \par\includegraphics[height=8.1cm,width=8.5cm,clip]{0597fig1.ps}\end{figure}$ Figure 1: X-ray $\beta$ profile of galaxy clusters with the slope parameter $\beta =2/3$ , the core radius $150~h^{-1}~{\rm kpc}$ at different redshifts, convolved with the point spread functions of RASS-3 for the energy 1.25 keV and normalized according to Eq. (5). The RASS-3 point spread function closely resembles the curve labeled z=1.00.
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In the text

$\begin{figure} \par\includegraphics[height=10cm,width=15.75cm,clip]{0597fig2.ps}\end{figure}$ Figure 2: Maximum likelihood contours ( $1\sigma$ , $2\sigma$ ...) for RASS-3 in the energy range 0.5-2.0 keV. Crosses mark objects found in the merged ROSAT Bright and Faint (RBF) Source Catalogues. Bright X-ray sources at ( ${\rm RA}=20.7^\circ$ , ${\rm Dec}=-0.70^\circ$ ), ( ${\rm RA}=33.65^\circ$ , ${\rm Dec}=-0.775^\circ$ ), ( ${\rm RA}=40.675^\circ$ , ${\rm Dec}=-0.025^\circ$ ) and ( ${\rm RA}=54.20^\circ$ , ${\rm Dec}=0.60^\circ$ ) have been removed from the RASS-3 photon maps. Note that RBF sources are also shown slightly outside of the SDSS Declination range [-1.25,+1.25] degrees.
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In the text

$\begin{figure} \par\includegraphics[height=10cm,width=15.75cm,clip]{0597fg3a.ps}... ...{10mm} \includegraphics[height=10cm,width=15.75cm,clip]{0597fg3b.ps}\end{figure}$ Figure 3: Maximum likelihood contours based on RASS-3 X-ray photons (1st and 4th panels, $1\sigma$ , $2\sigma$ , ..., contours), SDSS galaxies (2nd and 5th panels, $\ge$ $10\sigma$ ) and the combined maximum likelihood contours of RASS-3 and SDSS data (3rd and 6th panels, $\ge$ $10\sigma$ ). Crosses mark the position of the deepest X-ray cluster samples available sofar (REFLEX-2, X-ray flux limit 1.8 $\times$ $10^{-12}~{\rm erg}~{\rm s}^{-1}~{\rm cm}^{-2}$ ). Squares mark the position of the X-ray clusters of the final sample. The structure at ${\rm RA}=30$ deg and ${\rm Dec}=+0.5$ deg has a too low likelihood in the SDSS galaxy distribution and is thus not included in the final catalogue.
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In the text

$\begin{figure} \par\includegraphics[height=10cm,width=15.75cm,clip]{0597fig4.ps}\end{figure}$ Figure 4: Maximum likelihood contours. Symbols as in Fig. 3. Squares mark the position of the X-ray clusters of the final sample.
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In the text

$\begin{figure} \par\includegraphics[height=7.25cm,width=7.85cm,clip]{0597fig5.ps}\end{figure}$ Figure 5: Cumulative X-ray cluster number counts of the RASS/SDSS clusters (histograms) for a log-likelihood minimum of 15 applied to the SDSS data (continuous line), for 25 (lower dashed line), and for 5 (upper dashed line). The RASS/SDSS cluster counts are compared with results obtained with other surveys (points with $1\sigma$ error bars: with RDCS from Rosati et al. 1998 converted to the ROSAT energy band 0.1-2.4 keV assuming a Raymond-Smith spectrum with z=0, $k_{\rm B}T=5$ keV, and solar abundance, with REFLEX, and REFLEX-2). No corrections for variations of the angular survey sensitivity (effective survey area) are applied to the RASS/SDSS and REFLEX-2 data (see main text).
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In the text

$\begin{figure} \par\includegraphics[height=6.9cm,width=7.1cm,clip]{0597fig6.ps}\end{figure}$ Figure 6: Fraction of sources with minimum source counts $N_{\rm ph}$ as obtained with the matched filter for the final X-ray cluster sample derive in Sect. 5.
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In the text

$\begin{figure} \par\includegraphics[height=7.6cm,width=7.95cm,clip]{0597fig7.ps}\end{figure}$ Figure 7: Comparison of countrates obtained with the matched filter $\Lambda$ and with the growth curve analysis ctr(GCA) for the final X-ray cluster sample. Not shown are clusters partially outside the test area (1 cluster) and clusters where GCA could not find a clear flattening of the background-subtracted countrates beyond the so-called outer significance radius (6 clusters).
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In the text

$\begin{figure} \par\includegraphics[height=7.6cm,width=7.95cm,clip]{0597fig8.ps}\end{figure}$ Figure 8: Comparison of countrates obtained from RASS-3 with countrates as given in the 2nd ROSAT Source Catalog of Pointed Observations with the Position Sensitive Proportional Counter. The comparison includes all types of X-ray sources.
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In the text

$\begin{figure} \par\includegraphics[height=7.6cm,width=8cm,clip]{0597fig9.ps}\end{figure}$ Figure 9: Comparison of cluster redshifts estimated from the SDSS data with spectroscopic cluster redshifts (see Tables 2 and 3).
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In the text

$\begin{figure} \par\includegraphics[height=9.95cm,width=8.5cm,clip]{0597f10a.ps}... ...*{4mm} \includegraphics[height=9.95cm,width=8.5cm,clip]{0597f10b.ps}\end{figure}$ Figure 10: RS17 ( left) at z=0.1092 with the X-ray flux S=1.4 $\times$ $10^{-12}~{\rm erg}~{\rm s}^{-1}~{\rm cm}^{-2}$ in the ROSAT energy range 0.1-2.4 keV. RS28 ( right) at z=0.2745 with S=1.3 $\times$ $10^{-12}~{\rm erg}~{\rm s}^{-1}~{\rm cm}^{-2}$ .
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In the text

$\begin{figure} \par\includegraphics[height=9.95cm,width=8.5cm,clip]{0597f11a.ps}... ...*{4mm} \includegraphics[height=9.95cm,width=8.5cm,clip]{0597f11d.ps}\end{figure}$ Figure 11: RS7 ( upper left) at z=0.0581 with the X-ray flux S=5.4 $\times$ $10^{-13}~{\rm erg}~{\rm s}^{-1}~{\rm cm}^{-2}$ in the ROSAT energy range 0.1-2.4 keV. The cluster is not in the Bahcall et al. (2003) sample. RS26 ( upper right) at z=0.0663 with S=5.1 $\times$ $10^{-13}~{\rm erg}~{\rm s}^{-1}~{\rm cm}^{-2}$ is not in the Bahcall et al. (2003) and Goto et al. (2002a) catalogues. RS53 ( lower left) at z=0.0425 with S=3.7 $\times$ $10^{-12}~{\rm erg}~{\rm s}^{-1}~{\rm cm}^{-2}$ is not in the Bahcall et al. and Goto et al. catalogues. RS75 ( lower right) at z=0.1822 with S=1.3 $\times$ $10^{-12}~{\rm erg}~{\rm s}^{-1}~{\rm cm}^{-2}$ is not in the Bahcall et al. and Goto et al. catalogues. The cluster is also not in the RBF sample extracted from RASS-2 (Voges et al. 1999).
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In the text

$\begin{figure} \par\includegraphics[height=6.25cm,width=7.1cm,clip]{0597f12a.ps}... ...*{7mm} \includegraphics[height=6.25cm,width=7.1cm,clip]{0597f12b.ps}\end{figure}$ Figure 12: Upper panel: Cumulative distribution of the negative logarithmic Kolmogorov-Smirnov probability for a point source. The vertical line marks the threshold below which clusters are expected to be point-like in RASS-3. Lower panel: Cumulative distribution of the normalized differences between the observed hardness ratios to the theoretically expected hardness ratios for a 5 keV cluster, normalized to the error of the hardness ratio measurement. The vertical line marks the threshold below cluster fluxes are expected to be significantly contaminated by AGN. All quantities are determined with the GCA method.
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In the text

$\begin{figure} \par\includegraphics[height=7.5cm,width=5.9cm,clip]{0597f13a.ps}\... ...e*{3cm} \includegraphics[height=7.5cm,width=5.9cm,clip]{0597f13b.ps}\end{figure}$ Figure 13: X-ray luminosity vs. redshift for the total cluster sample ( upper left), for clusters not in the Goto et al. (2002a) sample ( lower left), for clusters not in the Bahcall et al. (2003) sample ( upper right), and for the clusters neither in Goto et al. and Bahcall et al. ( lower right). The redshifts used are estimated from the SDSS data with the matched filter described in Sect. 4.
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In the text

$\begin{figure} \par\includegraphics[height=6.8cm,width=7.2cm,clip]{0597fi14.ps}\end{figure}$ Figure 14: Redshift histogram of the clusters with spectroscopic redshifts. Filled steps show the redshift distribution of the clusters which are in common with Goto et al. (2002a) and Bahcall et al. (2003).
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In the text

$\begin{figure} \par\includegraphics[height=8.1cm,width=8.5cm,clip]{0597fig1.ps}\end{figure}$	Figure 1: X-ray $\beta$ profile of galaxy clusters with the slope parameter $\beta =2/3$ , the core radius $150~h^{-1}~{\rm kpc}$ at different redshifts, convolved with the point spread functions of RASS-3 for the energy 1.25 keV and normalized according to Eq. (5). The RASS-3 point spread function closely resembles the curve labeled z=1.00.
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$\begin{figure} \par\includegraphics[height=10cm,width=15.75cm,clip]{0597fig4.ps}\end{figure}$	Figure 4: Maximum likelihood contours. Symbols as in Fig. 3. Squares mark the position of the X-ray clusters of the final sample.
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$\begin{figure} \par\includegraphics[height=6.9cm,width=7.1cm,clip]{0597fig6.ps}\end{figure}$	Figure 6: Fraction of sources with minimum source counts $N_{\rm ph}$ as obtained with the matched filter for the final X-ray cluster sample derive in Sect. 5.
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$\begin{figure} \par\includegraphics[height=7.6cm,width=7.95cm,clip]{0597fig7.ps}\end{figure}$	Figure 7: Comparison of countrates obtained with the matched filter $\Lambda$ and with the growth curve analysis ctr(GCA) for the final X-ray cluster sample. Not shown are clusters partially outside the test area (1 cluster) and clusters where GCA could not find a clear flattening of the background-subtracted countrates beyond the so-called outer significance radius (6 clusters).
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$\begin{figure} \par\includegraphics[height=7.6cm,width=7.95cm,clip]{0597fig8.ps}\end{figure}$	Figure 8: Comparison of countrates obtained from RASS-3 with countrates as given in the 2nd ROSAT Source Catalog of Pointed Observations with the Position Sensitive Proportional Counter. The comparison includes all types of X-ray sources.
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$\begin{figure} \par\includegraphics[height=7.6cm,width=8cm,clip]{0597fig9.ps}\end{figure}$	Figure 9: Comparison of cluster redshifts estimated from the SDSS data with spectroscopic cluster redshifts (see Tables 2 and 3).
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$\begin{figure} \par\includegraphics[height=9.95cm,width=8.5cm,clip]{0597f10a.ps}... ...*{4mm} \includegraphics[height=9.95cm,width=8.5cm,clip]{0597f10b.ps}\end{figure}$	Figure 10: RS17 ( left) at z=0.1092 with the X-ray flux S=1.4 $\times$ $10^{-12}~{\rm erg}~{\rm s}^{-1}~{\rm cm}^{-2}$ in the ROSAT energy range 0.1-2.4 keV. RS28 ( right) at z=0.2745 with S=1.3 $\times$ $10^{-12}~{\rm erg}~{\rm s}^{-1}~{\rm cm}^{-2}$ .
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$\begin{figure} \par\includegraphics[height=6.8cm,width=7.2cm,clip]{0597fi14.ps}\end{figure}$	Figure 14: Redshift histogram of the clusters with spectroscopic redshifts. Filled steps show the redshift distribution of the clusters which are in common with Goto et al. (2002a) and Bahcall et al. (2003).
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