Left: two mock slits for the slit 1 of our 2016 observations (see Fig. 1), placed on the image of the galaxy acquired during the night of the observation. The two mock slits (green and red) are shifted apart by 1″, with the green slit marking the best slit position obtained in our simulation. Right: luminosity profile along the two mock slits are shown in the left panel (from top to bottom). The blue curve is the luminosity distribution passing through the slit obtained from the 2D spectrum (L_slit(pixel)) of the slit 1 observation (integrated over wavelength to be consistent with the image).