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In search of reionization:

In search of reionization:. Confessions of a self-avowed Hubble Hugger. When was the last time your average Baryon did something interesting?. Like a phase transition or a cool party or something… (James Rhoads) Answer: z> 6….more than 12.5 Gyrs ago.

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In search of reionization:

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  1. In search of reionization: Confessions of a self-avowed Hubble Hugger

  2. When was the last time your average Baryon did something interesting? Like a phase transition or a cool party or something… (James Rhoads) Answer: z> 6….more than 12.5 Gyrs ago. Know when you'll be speaking. A speech heavy on content is perfectly acceptable in the morning when audiences are fresh and attentive, but not at the end of the day or following a meal. Typically, a late-day presentation would be kept light and more entertaining…And let your audience know you're doing so; they'll appreciate your sensitivity and be more inclined to tune in….(advice from STScI website for speakers).

  3. Detection of G-P trough.

  4. The Lyman- ReionizationTest Ionized IGM Continuum Photons To Youngstarburst Observer Lyman- photons

  5. 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)

  6. 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)

  7. 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

  8. Lyman- Luminosity Functions (Malhotra & Rhoads 2004) • 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!

  9. Major methods to probe reionization • GP test: Explores end of reionization; saturates at neutral fractions ~ 1% • CMBR: Integral constraint; probes entire history with one measurement butlacks detailed history • 21 cm: Promising, but unproven. We first expect statistical results; mappingmaybe later. • LyA: Probes ~50% neutral fractions; Local; may allow bubble mapping with large anddeep samples. Bottom line: Complementary methods, want to combine all!

  10. The volume test:(Malhotra & Rhoads, 2006) Suppose each Lyman- emitter is visible because of a local Stromgren sphere, created by neighboring undetected dwarf galaxies, hidden AGNs, decaying dark matter, 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 • Get a filling factor: f = n V. • The required volume ionized fraction is then roughly 1 - exp(-f). • Correlations modify the higher order terms. < 30% neutral by volume.

  11. MR99 MR03 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)

  12. Ly- Luminosity Functions Revisited • Kashikawa et al (2006) and Shimasaku et al (2006) - LyA luminosity functions at z=6.5 and z=5.7. • Find apparent bright end evolution. Interpretation: • Neutral IGM? But: LF shape change not as expected • True LF evolution (Dijkstra et al 2007)? • Field to field variations?

  13. Z = 6.5 state of the art • Figure from Kashikawa et al 2006 • H Yan’s candidates (circa 2009) added as green stars. • HCM 6a and LALA points as cyan stars • Santos lensing upper limits as purple arrows

  14. Luminosity function comparisons, again • The scatter among different LF determinations, at fixed L and fixed z=5.7, is about 0.2 dex, nearly a factor of 2. • Steep slope! So… • The offset in the log(L) direction is as little as 0.1 dex (25%). • Good, consistent calibration of counts to luminosity matters here.

  15. Suppose all we can do is a sloppy job - clustering, evolution etc. Go to higher redshifts --- the effect of reionization should be more dramatic!

  16. Iye et al. Ota et al. 2008 -- Z=6.9

  17. Tilvi et al. 2010 4 candidates using NEWFIRM at KPNO.

  18. Z=7.7 (Pascale et al. 2010) & candidates from CFHT WIRCAM

  19. OH forest from the ground

  20. HST/JWST has no such constraints Straughn et al. 2010, based on ER Science time. Simulations: Pirzkal et al. 2008

  21. With GRAPES we have spectroscopically confirmed LBGs to z’(AB)=27.5, 10 times deeper in flux than Keck/VLT.

  22. With a combination of wide-field ground based instrumentation and uninterrupted redshift range from space, we can map reionization using Lya galaxies as probes. • Local, scalable solution with proven techniques…all we need is telescope time and lots of it.

  23. Much of the work mentioned here got started when I was a Hubble Fellow, and later staff at STScI ---- Many thanks to everyone! The right way to begin is to pay attention to the young, and make them just as good as possible --- Socrates I don't care to belong to a club that accepts people like me as members --- Groucho Marx

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