Comparison between the V-band magnitudes estimated from our polarimetric observations and the Gaia DR3 B_P-band photometry for the cross-matched stellar sample. The color scale indicates the density of points, and the dashed line shows the best-fit linear regression, V = 0.99 B_P − 0.17. The tight correlation and small scatter demonstrate the reliability of the V-band magnitude calibration adopted for our optical polarization catalog.