Chemical enrichment at high redshifts

We have tried to understand the recent observations related to metallicity in Ly-alpha forest clouds in the framework of the two component model. The model consists of mini-halos having circular velocities smaller than simila r to 55 km s(-1), with no star formation and galactic halos with higher cir cular velocities less than or equal to 250 km s(-1), having clouds, star fo rmation and consequent metal enrichment. We find that even if the mini-halo s were chemically enriched by an earlier generation of stars, to have [C/H] similar or equal to -2.5, the number of C IV lines with column density > 1 0(12) cm(-2), contributed by the mini-halos, at the redshift of 3, would be only about 10% of the total number of lines, for a chemical enrichment rat e of (1 + z)(-3) in the galaxies. Recently reported absence of heavy elemen t lines associated with most of the Ly-alpha lines with HI column density b etween 10(13.5) cm(-2) and 10(14) cm(-2) by Lu er al [13], if correct, give s an upper limit on [C/H] = -3.7, not only in the mini-halos, but also in t he outer parts of galactic halos. However, the mean value of 7 x 10(-3) for the column density ratio of C TV and HI, determined by Cowie and Songaila (1998) for low Ly-alpha optical depths, implies an abundance of [C/H] = -2. 5 in mini-halos as well as most of the region in galactic halos. The redshi ft and column density distribution of C IV has been shown to be in reasonab le agreement with the observations.