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We present the results of deep multicolour CCD imaging with the 6-m telescopeof the pair of extremely metal-deficient gas-rich dwarf galaxies SBS 0335-052 Eand W. The total magnitudes in U,B,V,R,I bands and the integrated fluxes ofH-alpha emission are measured for both galaxies, and their integrated coloursare derived. The analysis of their surface brightness (SB) distributions isperformed with the use of the azimuthally-averaged SB profiles. The latter weremodeled by the central Gaussian component and the underlying exponential`disk', mainly contributing in the outermost, very low SB regions. The coloursof these LSB components are used to estimate the age of the oldest visiblestellar population. For the interpretation of the observed LSB colours theircontamination by the nebular emission of ionized gas is accounted for by theuse of the distribution of H-alpha flux. We compare the derived `gas-free'colours with the colours predicted by the evolution synthesis models from thePEGASE.2 package, considering three SF histories: a) instantaneous starburst,b) continuous star formation with constant SFR, c) continuous exponentiallyfading SF (e-fold time of 3 Gyr). We conclude that the `gas-free' colours ofthe LSB component of the E galaxy can be best consistent with the instantaneousstarburst population (ages of less than ~100 Myr). Models with continuous SFgive less consistent results, but can be considered as acceptable. For suchscenarios, the `gas-free' colours require ages of less than ~400 Myr. For the Wgalaxy, the situation is in general similar. But the colour (V-R) appears to bequite red and implies a significantly older component. We briefly discuss thepossible evolution sequence between SBS 0335-052, HI 1225+01 and otherextremely metal-deficient galaxies based on the merger scenario.Comment: 16 pages, 6 figures, 6 tables, accepeted to A&A 2 March 200

SBS 0335–052 E and W: Implications of new broad-band and Hα photometry