Observed radial velocity vs. the luminosity distance. The circles and triangles indicate the sources at the positive and negative Galactic longitudes, respectively. The dotted curves are radial velocities expected at ﹩l=\pm 3^{\circ }﹩, from the approximate Galactic rotation curve, ﹩V_{\mathrm{rot}\,}=200\,\mathrm{km\,s}\,^{-1}\times R\times ( 8.0+R_{a}) / [ 8.0\times ( R+R_{a}) ] \times ( 1+1.1/ [ 1+3\times ( R-R_{a}) ^{2}] ) ﹩. Here R is the distance from the Galactic center in kpc and R_a is an adjustable parameter to create a peak of the rotation curve near R_a and is adopted as 0.3 kpc.