Angular sizes of the faint blue galaxies

We investigate the angular sizes, morphologies rind B - I colours of the 21 less than or equal to I less than or equal to 24 galaxies imaged on 10 Wide Field Planetary Camera fields, The number of galaxies with bluer colours (B - I < 2.0) and moderately large angular sizes exceeds nonevolving predictions by a factor of similar to b2, but is consistent with pure L* evolution (PLE) models, There is also an excess of galaxies of smaller angular size with very blue B - I colours, suggesting the presence of a lower redshift starburst dwarf galaxy population, with a steep luminosity function. The bluest (B - I < 1.2) subsample, consisting of 57 galaxies at 21 < I < 23, contained galaxies with a wide range of angular size and morphology, including spirals, chain galaxies, irregulars and bulge-profile nucleated galaxies, The blue spirals and chain galaxies tend to have the lowest apparent surface brightness, suggesting that they are mostly evolving L* galaxies at higher (z similar to 0.8-2.0) redshifts, while many of the others, with smaller angular sizes, may be starburst dwarf galaxies at z < 0.5. At least 16 of these very blue galaxies appear to be interacting, but we find no overall correlation between B - I colour and the presence of a near neighbour, The angular size distribution of the bluest galaxies is peaked at smaller angular sizes than the PLE model predictions, suggesting that the mean half-light radius of spiral galaxies has increased with time by similar to 25 per cent since z similar to 1.2. Blue galaxies of spiral morphology tend to have larger (by similar to 0.2 dex) half-light radii in the blue band than in the I band, indicating strong radial colour gradients.