3C 58 is a Crab-like supernova remnant containing the young pulsar PSR J0295+6449, which powers a radio plerion and a compact torus-like pulsar wind nebula visible in X-rays. We have performed a deep optical imaging of the 3C 58 field with the Nordic Optical Telescope in the B and V bands to detect the optical counterpart of the pulsar and its wind nebula. We analyzed our data together with the archival data obtained with the Chandra/ACIS and HRC in X-rays and with the Spitzer/IRAC in the mid-infrared. We detect a faint extended elliptical optical object with B=24.06+/-0.08 and V=23.11+/-0.04 whose peak brightness and center position are consistent at the sub-arcsecond level with the position of the pulsar. The morphology and orientation of the object are in excellent agreement with the torus region of the pulsar wind nebula, seen almost edge on in the X-rays, although its extension is only about a half of that in X-rays. This suggests that in the optical we see only the brightest central part of the torus with the pulsar. The object is also practically identical to the counterpart of the torus region recently detected in the mid-infrared. We estimate that the contribution of the pulsar to the observed optical flux is less about 10%. Combinig the optical/mid-infrared fluxes and the X-ray power-law spectrum extracted from the spatial region constrained by the optical/infrared source extent we compile a tentative multi-wavelength spectrum of the central part of the nebula. Within the uncertainties of the interstellar extinction towards 3C 58 it is reminiscent of either the Crab or PSR B0540-69 pulsar wind nebula spectra. These properties of the detected object strongly suggest it to be the optical counterpart of the 3C 58 pulsar + its wind nebula system. This makes 3C 58 the third member of such a class of the torus-like pulsar+nebula systems identified in the optical and mid-infrared.
The paper has been submitted for publication in A&A and published in astro-ph/0802.2386