ON THE ORIGIN OF LOW-SURFACE-BRIGHTNESS GALAXIES

We reconsider the problem of the origin of low-surface-brightness (LSB ) galaxies within the standard Cold Dark Matter (CDM) cosmological mod el (Omega = 1, h = 0.5). Taking into account the effect of substructur e on the collapse times of low overdensity peaks, we show that the abu ndance of these peaks is larger than previously expected because of th e dragging caused by dynamical friction induced by the presence of sma ll-scale substructure. The number density of these shallow, low-densit y peaks turns out to be in good agreement with the observed overdensit y of the blue LSB galaxies found during recent surveys.