Distribution of the offset angles between the orientations of B-fields and the ridge in ρ Oph-A, as a function of A_V (circle symbols). The data in gray color represent the offset angle collected within the black circle “I” centered at the position of the Oph-S1 star with a radius of 60″ in Fig. 9. The data in blue and green additionally represent the offset angle collected within the two rings “II” and “III” in Fig. 9, respectively. The red diamonds represent the median value of the offset angles in each interval of A_V=3 mag. The number of red diamonds is reduced to improve the clarity of the figure. The red curve connecting all the red diamonds shows the trend of the offset angles vs. A_V in ρ Oph-A. The cyan box indicates the range of A_V=42–60 mag where relative orientation between B-fields and the ridge changes from parallel to perpendicular. The gray horizontal dashed lines indicate perpendicular, 45°, and parallel relative orientations of B-fields with respect to the ridge.