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Low-redshift evolution of the Lyman-alpha Forest

T. Theuns·A. Leonard·G. Efstathiou
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Abstract

The low-redshift evolution of the intergalactic medium is investigated using hydrodynamic cosmological simulations. The assumed cosmological model is a critical density cold dark matter universe. The imposed uniform background of ionizing radiation has the amplitude, shape and redshift evolution as computed from the observed quasar luminosity function by Haardt & Madau. We have analysed simulated Lyman-alpha spectra using Voigt-profile fitting, mimicking the procedure with which quasar spectra are analysed. Our simulations reproduce the observed evolution of the number of Lyman-alpha absorption lines over the whole observed interval of z=0.5 to z=4. In particular, our simulations show that the decrease in the rate of evolution of Lyman-alpha absorption lines at z< 2, as observed by Hubble Space Telescope, can be explained by the steep decline in the photo-ionizing background resulting from the rapid decline in quasar numbers at low redshift.

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T. Theuns, A. Leonard, G. Efstathiou. 1998-03-20. Low-redshift evolution of the Lyman-alpha Forest. https://doi.org/10.1046/j.1365-8711.1998.01740.x

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