Cosmological Radiative Transfer and the Line-of-Sight Proximity Effect

¹ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
² Institute of Astronomy, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria

Abstract

We study the proximity effect around high redshift quasars in dependence on the quasar redshift and environment using 3D continuum radiative transfer simulations. Snapshots of dark matter only simulations at redshift 3, 4, and 4.9 are mapped to hydrogen densities and temperatures using an effective equation of state. The overionization zone around QSOs with luminosities L_νHI = 10³¹and10³²   ergHz^-1s^-1 is studied in a UV background field in radiation equilibrium. By analyzing synthetic spectra of lines of sight originating at the QSO, the proximity effect is studied. We find that the quasar spectral energy distribution, diffusion and shadowing due to Lyman Limit systems play a role in the signal. Density inhomogeneities around the QSO are responsible for a large scatter around the mean proximity effect seen in all simulated QSO spectra. This scatter is larger than the differences arising from varying quasar host environments.