The Proximity Effect in Quasar Spectra as an Astrophysical Tool

• Applicant: Professor Dr. Lutz Wisotzki
• Subject Area: Astrophysics and Astronomy
• Term: from 2007 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 35039570

We propose a comprehensive investigation of the 'proximity effect' in the spectra of high-redshift quasars. This phenomenon describes the reduced absorption by intergalactic hydrogen (and also helium) by the action of individual quasars. These provide additional ionizing photons in excess to those from the cosmic UV background, leading to a reduction of neutral gas column densities on Mpc-scales around the quasars. We have drafted a set of observational experiments to exploit the proximity effect as an astrophysical tool. The guiding scientific question of our investigation is how the cosmic UV background (UVB) is formed and influenced by discrete sources. The observations will be complemented by and calibrated with results from gasdynamical simulations of cosmological structure formation. We will be able to estimate the intensity of the UVB and its evolution with redshift with unprecedented statistical accuracy. We will study the connection between individual quasars and spectral fluctuations of the UVB. These measurements will provide insights into the radiative transfer properties of the universe in the 'quasar epoch' around z ~ 2-4. At the same time we will be able to constrain some fundamental, but poorly known quantities of quasars: Their life times, and the degree of anisotropy in the quasar radiative output.

• DFG Programme: Research Grants