- Conference date: 7-9 October 2002
- Location: College Park, Maryland (USA)
We determine the evolution of the faint, high‐redshift, optical luminosity function of Active Galactic Nuclei (AGN) implied by several observationally‐motivated models of the ionizing background from 3 < z < 5. Our results depend crucially on whether we use the total ionizing rate measured by the proximity effect technique or the lower determination favored by the flux decrement distribution of Lyα forest lines. In addition, there is an unknown contribution to the ionizing background from stars, which we parameterize by the escape fraction of ionizing photons, f esc (recent estimates have it at 16% for z ∼ 3). Increasing the contribution from stars further limits the number of AGN necessary for a given ionizing background. By comparing our expectations to faint AGN searches in the HDF and high‐z galaxy fields, we find that typically‐quoted proximity effect estimates of the background imply an over‐abundance of AGN compared to the faint counts (even with f esc = 1). Even adopting the lower bound on proximity effect measurements, the stellar escape fraction must be high: f esc ≳0.2. Conversely, the lower flux‐decrement‐derived background requires a smaller number of ionizing sources, and faint AGN counts are consistent with this estimate only if there is a limited stellar contribution, f esc ≲0.05. Our full development and results can be found in .
- Active galaxies
- Superconducting proximity effects
- Galactic evolution
- Galactic luminosities
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