J1000+12. GTC continuum and Hα images. Contour values start at 3σ and increase with factor of two or three for the continuum and Hα images, respectively. For the Hα image, σ = 3.8 × 10⁻¹⁹ erg⁻¹ cm⁻² pixel⁻¹. Right panel: Hα emission in a smaller region centred on the QSO2 with a different colour palette. The small green * symbol in the middle panel shows the expected location of the TDG candidate identified in the continuum image. Several additional features mentioned in the text are indicated with purple arrows.