Physical state of the intergalactic medium at redshifts<i>z</i>= 2-4

We use two large surveys of quasars (QSOs), namely, 2QZ-6QZ and SDSS DR1, to estimate mean properties of the background ultraviolet (UV) radiation and the temperature of intergalactic gas at redshifts z 2-4. We show that the intensity of the UV background radiation as estimated by We also briefly discuss spatial variations of both the intensity of background UV radiation and the gas temperature. These variations can be studied in more detail with high-resolution observations of the proximity effects, Lyman absorbers and metal systems. Using the minimal spanning tree technique, we analyse the spatial distribution of QSOs and show that it is quite similar to random (Poissonian).

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