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Evolution of the Reionization: Insights from He II Ionizing Background

This talk by Keri Dixon from UCLA and Steven Furlanetto explores the evolution of the reionization using ionizing background data. The discussion includes the He-ionizing flux, attenuation length, and uncertainties in emissivity. The focus is on regions like tHe II HE 2347-4342, HS 1700+64, Q0302-003, HS 1157+3143, and PKS 1935-692, examining the Gunn-Peterson optical depth and the impact of varying ionized fractions. The analysis considers the isothermal equation of state and the influence of fluctuating vs uniform Helium reionization driven by quasars. The presentation discusses the impact on R0 and G at different redshifts and addresses potential variations from expected curves. The study aims to identify potential markers for reionization and determine the significance of events around z ~ 2.75. Possible conclusions include affirming the reionization process, questioning the model's adequacy, or exploring temperature dependencies for further insights.

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Evolution of the Reionization: Insights from He II Ionizing Background

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Presentation Transcript

  1. Evolution of the Reionization @ Ringberg 25.03.2009 He-ionizing background Keri Dixon University of California, Los Angeles Steven Furlanetto

  2. Looking for the photoionization rate Assume background ionization flux: The attenuation length R0 is treated as an unknown. When convenient, choose Bolton et al. 2006 The emissivity en is also uncertain.

  3. Begin with tHe II HE 2347-4342:Zheng et al. 2004, Shull et al. 2004, Kriss et al. 2001 HS 1700+64: Fechner et al. 2006, Davidsen et al. 1996 Q0302-003: Heap et al. 2000, Hogan et al. 1997 HS 1157+3143: Reimers et al. 2005 PKS 1935-692: Anderson et al. 1996

  4. From teff to G Start with the Gunn-Peterson optical depth Balance photoionization and recombination for HeII Introduce the fractional density of the IGM (D) with p(D) Miralda-Escudé et al. 2000 Assume isothermal equation of state

  5. Fluctuating vs. Uniform Helium reionization driven by quasarsfluctuating G Uniform ~ R0 = ∞ The attenuation length and ionized fraction affect distribution. Furlanetto 08

  6. Evolution of G Choose convenient R0 Pin to curve at z = 2.45 Significant departure from curve z ~ 2.75 (?) Uncertain (mainly) due to limited lines of sight

  7. Evolution of R0 Choose convenient G Pin to curve at z = 2.45 Significant jump z ~ 2.75 (?) Fluctuating background smoothes evolution

  8. What do we see? Choose convenient R0 Assume convenient G Find expected teff Data could distinguish the three regimes

  9. Where’s reionization?

  10. Time for lunch…just kidding It seems like probably something is happening around z ~ 2.75 Possible conclusions: Reionization is happening near this redshift This “something” does not indicate reionization The model is an insufficient approximation

  11. Including T-dependence

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