The origin of intergalactic metals around Lyman-break galaxies

Abstract

Theoretical and observational arguments suggest that the intergalactic medium (IGM) might have been polluted with metals produced by early star formation. In this scenario, Lyman-break galaxies (LBGs) at redshift z=3 are likely to be surrounded by old metal bubbles, relics of an era when the characteristic mass of galaxies was small and gas retainment more difficult. We find that pregalactic enrichment of the IGM from 10^8-10^{10} M_sun dwarf galaxies at 6<z<12 can quantitatively explain the high cross-correlation between CIV systems and LBGs observed at z=3. The reason is twofold. First, both LBGs and high-z dwarfs are biased tracer of the mass distribution and form from exceptionally high density fluctuations which are strongly clustered. Second, the action of gravity tends to increase the spatial association between metal bubbles and LBGs. Our analysis shows that, in order to match the abundance of CIV systems observed at z=3, the metal bubbles generated by high-z dwarfs must have comoving sizes of ~100 kpc. We conclude that the observed galaxy-CIV spatial association needs not to be generated by late ``superwinds'' from LBGs.