The data used in this study are based on public data released from the VLT/UVES Commissioning and Science Verification and from the OPC program 65.O-0296A (P.I. S. D'Odorico) at the VLT/Kueyen telescope, ESO,Paranal, Chile.

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Schaye et al. (2000) adopted a threshold of 1 AMD, which results in a power law fit with higher $\chi^{2}$ .

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...1996)

The previous section suggests there is a contribution from sources other than QSOs to the UV background. Estimates of contributions from galaxies depend on many factors, such as the galaxy luminosity function and the galaxy emissivities. Including a contribution from galaxies, Shull et al. (1999) derive a UV background decreasing from $z \sim 2.5$ to $z \sim 1$ , similar to the QSO-dominated $J_{\rm HM}$ . On the other hand, Bianchi et al. (2001) find a non-decreasing J from $z \sim 5$ to $z \sim 1$ .

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