How fast is the evolution of the diffuse ultraviolet cosmic background radiation ?

Stanek, Krzysztof Z.

Poland

Abstract

Lyα absorption lines observed in Hubble Space Telescope UV spectra of 3C 273 have neutral hydrogen column densities comparable with those of z ~ 2 quasars. Assuming the standard pressure-confined model of Lyα clouds, we use this fact to determine the evolution of UV background radiation for z < 2. We find that to fit the data the UV background must evolve as (1+z)^5.0+/-1.2^ for z < 2. We also give constraints on the present value of the pressure of the intergalactic medium.

1992 Monthly Notices of the Royal Astronomical Society
eHST 1