The chemical build-up in the Universe is one of the major factors behind the evolution of galaxy populations across cosmic time. The metals ejected into the surrounding media through galactic feedback processes and the nature of ionising radiation shaped the galaxies as we see them in the present epoch. Studying evolution of metal absorbers across redshift, thus, provides valuable hints to the way the galaxy populations transformed across different epochs. Previous works on metal absorbers have used their number density statistics to infer various properties of the absorber galaxies such as galaxy halo size, metallicity, star formation rate, feedback processes and the nature of ionising radiation. The ESO VLT Large Program, the “Ultimate XSHOOTER legacy survey of quasars at z ranging from 5.8 − 6.6″ (XQR-30) has quadrupled the number of z~6 quasars with deep high-resolution spectra providing a unique opportunity to extend studies of metal absorbers across cosmic time. I will present the number density evolution of CII, OI and MgII including the first robust measurements of the evolution of weak MgII absorbers at redshifts ranging from 2 to 6. I will examine the origin of these absorbers and discuss what their evolution reveals about the chemical enrichment and the nature of ionising radiation in early Universe that shaped the galaxy evolution.
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