Top panel: blow-up of the p map shown in the top-right panel of Fig. 6 showing in more detail the red box where weestimated the magnetic-field strength of the C.1 shell. Bottom panel: column density map, N_H, of the CNM isolated with ROHSA. This is the same field of view shown in Fig. 6. Beside the red box shown in the top panel we also indicate two yellow boxes where we estimate the magnetic-field strength and compare it with C.1.