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Post GP-WMAP Reionization: the morning after

Post GP-WMAP Reionization: the morning after. We need quantitative measures of Epoch of reionization (Z reion ) Neutral fractions Volume fraction of ionized/neutral gas duration of reionization (  Z reion ) Sizes of bubbles: topology. Measuring reionization with Lyman-  emitters.

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Post GP-WMAP Reionization: the morning after

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  1. Post GP-WMAP Reionization: the morning after We need quantitative measures of Epoch of reionization (Zreion) Neutral fractions Volume fraction of ionized/neutral gas duration of reionization (Zreion) Sizes of bubbles: topology

  2. Measuring reionization with Lyman- emitters Lyman- galaxy test: neutral fractions, volume fractions local scaleable relevant at neutral fractions of <f(HI)>~0.1-0.5 Can be done with today’s technology (some progress already made) Complements GP, WMAP and 21 cm.

  3. The Lyman- ReionizationTest (Damping wing is a feature, not a bug) Ionized IGM Continuum Photons To Youngstarburst Observer Lyman- photons

  4. The Lyman-Test Neutral IGM Continuum Photons To Youngstarburst Observer Lyman- photons (Miralda-Escude 1998; Miralda-Escude & Rees 1998; Haiman & Spaans 1999; Loeb & Rybicki 1999)

  5. The Lyman- Test, First Order Concerns: HII Regions Neutral IGM Continuum Photons H II region To Youngstarburst Observer Lyman- photons (Madau & Rees 1999; Rhoads & Malhotra 2001; Haiman 2002)

  6. history Ly- lines were expected to be invisible in a neutral IGM until Hu et al. 2002 found a source at z=6.6. Then everyone rushed to explain why we could see Ly- even in a neutral IGM: ionized bubbles, winds … But hard to avoid attenuation of factors of 2-3 (Santos 2004) How do you know that any individual object was not intrinsically brighter? Statistical test on the population

  7. Lyman- Luminosity Functions • Luminosity function fits on all available data at z=5.7 and 6.5 • Santos et al. 2004, Taniguchi et al. 2004, Rhoads et al. 2004, Kurk et al. 2004, Tran et al. 2004, Hu et al. 2002, Hu et al. 2004, Ajiki et al. 2004, Rhoads et al. 2003, Rhoads & Malhotra 2001 (few tens of nights on large telescopes) • z = 6.5 plot shows two hypotheses: • z = 5.7 LF, or • z = 5.7 LF reduced by a factor of 3 in luminosity to approximate IGM absorption. • No evidence for neutral IGM!

  8. Charting Reionization There is no contradiction between the GP effect at z=6.2 and the Ly test at z=6.5; remarkable agreement with the dark gap tests (Fan et al. 2005)

  9. 1st order concern 1.Cosmic variance in samples Monte Carlo simulations to account for cosmic variance: All observed densities allowed to vary by factor of 2. • Circles: z = 5.7 • Triangles: z = 6.5 • Squares: z = 5.7 with L* divided by 3.

  10. 1st order concern 2.Picket fence effect Suppose you obliterate some fraction of the sources completely, and the other half remains untouched in luminosity. Then phi* should decrease - it is seen to increase slightly at z=6.5 compared to z=5.7

  11. Concern 3: redshift evolution: none seen so far! LALA Lum Fn at z=4.5 LALA Lum fn at z=4.5 (Dawson et al. 2005)

  12. 4. Bright end of luminosity function • See Haiman & Cen 2005, for luminosity dependent attenuation: the conclusions do not change significantly. • Higher luminosity objects possibly create larger ionized bubbles around themselves. • Furlanetto et al. 2005, conclude that neutral fraction is 50% compared to ~30% as in MR04.

  13. Stromgren spheres: • Rss= 0.7 Mpc/(1+z) {L43t8 (fesc/(1-fesc))}1/3 L* = 42.5 Age < 10 8 years Best estimate of Rss < 0.7x0.3 Mpc •  = 1.2 Mpc / Rss ~ 5 : optical depth at the line center

  14. Concern 5: Clustering around Ly-a sources • What about clustering and Stromgren spheres created by unseen sources around Lyman-alpha emitters at z=6.5? • Need to boost the ionizing flux by a factor of 10: possible in simulations: Wyithe & Loeb 2004, Furlanetto et al. 2004: • deep ACS imaging around one z=6.5 source shows no dramatic overdensity (Rhoads et al. in prep.) Stiavelli et al. 2005 see an overdensity at z=5.9 around a Sloan quasar at z=6.2 Agnostic about this possibility

  15. The volume test:(Malhotra & Rhoads, 2006, submitted) Suppose each Lyman- emitter is visible because of a local Stromgren sphere, created by neighboring undetected dwarf galaxies, hidden AGNs, tooth fairies … • We know the space density of Lyman- galaxies at z=6.5  > 1x10-4 cMpc-3 (Taniguchi et al. 2005) • Place each one in a ionized bubble of the smallest size to enable escape of half of the line flux in an otherwise neutral medium • [V(I)] > 4/3(RssMpc)3

  16. Getting the volume (details): • V=250 Km/s • T=50% • Rss=1.2 pMpc=1.2x7.5 cMpc • Number density • n > 1.2-1.8e-4 cMpc3

  17. Improvements: • Better luminosity functions: better constraints on T. At present T > 50%, but how much more? • Fainter sources, higher source density. • Velocity offsets. • Clustering of Ly-alpha galaxies.

  18. Shimasaku et al. 2005 at z=5.7

  19. Extension to redshifts z > 7 • Windows in the atmospheric OH spectrum continue into the J and H bands, though narrower. • Newest NIR cameras have A sufficient for plausible Ly- searches. • Several efforts under way… • Horton et al 2004 (DAzLE project): VLT + DAzLE) z ~ 7.7 • Smith et al (see Barton et al 2004): Gemini + NIRI, z ~ 8.2 • Willis et al (“ZEN” project): VLT +ISAAC, z ~ 8.8 • Cuby et al: VLT +ISAAC, z ~ 8.8

  20. Summary • Ly-a luminosity function test at z=6.5 implies neutral fraction x(HI)<50% at z=6.5 • Space density of observed Ly-a implies a volume fraction of ionized gas V(I) > 30%. • Limits on V(I) can be improved by going fainter and finding more galaxies, better luminosity functions and velocity offesets between Ly-a and other lines: JWST. • Can go to higher redshifts and track the evolution of reionization as a function of z: WFC3, JWST

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