X-ray luminosity vs. r-band optical luminosity for CONF-FGSs (blue circles), NOCONF-FGSs (blue crosses), and CLs (red dots). Error bars for the CL sample are omitted. Reference values for L_opt and L_X are shown. The blue solid and dotted lines indicate the fits for the CONF-FGS and ALL-FGS samples, and the red solid line is the fit for the CL sample. The magenta long-dashed and cyan dashed lines are the fits when using alternative X-ray luminosity estimates: L_X,BSC/FSC values for the CL sample and L_X,corr values for the CONF-FGS sample. The inset plot shows the 90% c.l. confidence ellipses corresponding to CONF-FGSs, NOCONF-FGSs, ALL-FGSs (solid, dot-dashed, and dotted blue curves), and CLs (solid red curve). Results for alternative X-ray luminosities are shown: L_X,BSC/FSC for CLs (magenta long dashed curve) and L_X,corr for CONF-FGSs (cyan dashed line).