Lower large panel: a VLA A-array map of the continuum emission of NGC 3556 at 20 cm (ISE). The asterisk identifies the optical center. The large black cross indicates the Hikinematic center given by King & Irwin (1997) with the relative error (dashed-line circle). The smaller blue cross near the upper right corner of the green dashed circle denotes the 2 μm peak. The pink triangle marks the position of Chandra source 35. The position of the water maser is indicated by the red X-mark. The multipointed star in the lower right edge indicates a position where some supernovae have been detected (see ISE). Upper left panel: naturally weighted contour image of the only compact nuclear radio continuum source, among those of ISE, detected in NGC 3556 at 1.4 GHz by MERLIN. Contours: –2.5, 2.5, 3, 3.5, 4, 4.5, 5 × 50 μJy/beam (1σ rms = 0.05 mJy beam^-1). Upper right panel: uniformly-weighted 1.4 GHz MERLIN contour image of the compact source. The star marks the water maser position. Contours: –3, 3, 3.5, 4 × 40 μJy/beam (1σ rms = 0.04 mJy beam^-1).