Difference in the continuum flux around [NII] λ 6583 between the observations in 2019 and 2021. A factor of 1.15 was applied to the 2021 observations to correct for differences in the flux calibrations (see Sect. 4). The proposed flow direction is indicated by a solid orange line, along with the edges in the [NII] λ 6583 contours displayed in Figs. 1 and 5 to highlight the path within the ISM.