Upper-left panel: TNG/DOLORES deep Hα image of the smudge region originally reported by Arias et al. (2022), corresponding to pointing P4 (see Table 2 and the green box in Fig. 2). The image is background-subtracted and with a logarithmic color scale. Upper right panel: same field as the upper left panel, but with additional continuum subtraction using a re-normalized TNG/DOLORES image in the R-band filter. The large green circle has a radius of 34.5 arcsec and encloses the large and brightest filaments, while the two small circles mark additional faint Hα line emission. Lower panel: X-ray image (same field of view as above) from the left panel of Fig. 2, overlaid with Hα contours at the level of 1.4 × 10^–17 erg cm^–2 s^–1 arcsec^–2, showing that the bright optical filament has a weak X-ray counterpart within the central region.