Example of PSF subtraction is shown from upper row to lower row, using the observation of [Fe II] of RW Aur as an example. The panels marked with color in the observation row show which channels were used to calculate the median PSF for the marked channel in the middle row. This empirical PSF is scaled to match the peak flux of the observation. When subtracting the scaled PSF, the residuals contain the extended emission for the specific line.