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Observational Constraints of of Reionization History in the JWST Era

Observational Constraints of of Reionization History in the JWST Era. Xiaohui Fan University of Arizona. Astrophysics in the Next Decade Sep 26, 2007. Background: 46,420 Quasars from the SDSS Data Release Three. reionization. Two Key Constraints: WMAP 3-yr: z reion =10+/-3

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Observational Constraints of of Reionization History in the JWST Era

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  1. Observational Constraints of of Reionization History in the JWST Era Xiaohui Fan University of Arizona Astrophysics in the Next Decade Sep 26, 2007 Background: 46,420 Quasars from the SDSS Data Release Three

  2. reionization Two Key Constraints: WMAP 3-yr: zreion=10+/-3 2. IGM transmission: zreion > 6 From Avi Loeb

  3. Outline • Current Observational Constraints • Probing reionization history in the next decade • Finding high-z sources • Observational tests for the neutral era • Two critical tasks related to JWST • Wide-field IR surveys for z>8 quasars • Comprehensive Ly  galaxy surveys at z~10 • Will not talk about: • 21cm probe • Future CMB polarization measurements • IR background and first stars

  4. Open Questions: • When did it happen: fHI vs. z • z~6: late • z~15: early • Extended or phase transition? • How did reionization proceed: • Homogeneous or large scatter? (fHI) vs. z • Topology of overlap; fHI vs.  • What did it: (gal, qso) vs. z • AGN? • Star formation? • Decay particles? • Observational goals • Map the evolution and spatial distribution of ionization state • Find highest redshift galaxies and quasars: source of reionization

  5. WMAP: early reionization? • WMAP third year: •  = 0.09+/- 0.03 • Larger signal comparing to late reionization model (but marginally consistent!) • However, no direct conflict to Gunn-Peterson result, which is sensitive only to ~1% neutral IGM • Overlapping could still be at z~6 • IGM could have complex reionization history  direct observation of high-z sources zreion = 6 Page et al., Spergel et al. 2006

  6. Gunn-Peterson Test • Classic G-P (1965) effect: • Saturates at low neutral fraction • G-P damping wing (Miralda-Escude 1998) • Sensitive to neutral IGM • Attenuates off-resonance transmissions Damping wing

  7. Evolution of Lyman Absorptions at z=5-6 z = 0.15

  8. Optical depth evolution accelerated z<5.7:  ~ (1+z)4.5 z>5.7:  ~ (1+z)>11 End of reionization? Evolution of neutral fraction fHI > 10-3 - 10-2 at z=6 Order of magnitude increase from z~5 G-P absorption saturates; needs more sensitive tests Accelerated Evolution at z>5.7 (1+z)11 (1+z)4.5 XF et al. 2006

  9. Beyond Gunn-Peterson Optical Depth:HII Region Sizes and Dark Gap Distributions zem • Size of HII region Rs ~ (LQ tQ / fHI )1/3 • Best estimate: fHI ~ a few percent at z~6 • Can be applied to higher z and fHI with lower S/N data Gallerani et al. Shapiro, Haiman, Mesinger, Wyithe, Loeb, Bolton, Haehnelt, Maselli et al. • Dark gap statistics • Sensitive to the topology of reionization • z~6 observations: • Dramatic increase in gap length: • Consistent with overlap at z~6-8 • Existence of transmission at z>6 places an upper limit of average neutral fraction <30% (Gallerani et al. 2007)

  10. Ly  Galaxy LF at z>6 • Neutral IGM has extended GP damping wing  attenuates Ly  emission line • New Subaru results • Declining density at z~6-7 (2-3 result) • Reionization not completed by z~6.5 • fHI ~ 0.3 - 0.6 at z~7 • Overlapping at z=6-7? • cf. Malhotra & Rhoads, Hu et al.: lack of evolution in Ly  galaxy density Iye et al. 2006 Kashikawa et al. 2006 Ota et al. 2007

  11. Detected to z=6.30 Advantages: Bright Small surrounding HII regions: could use damping wing of Gunn-Peterson trough to probe high neutral fraction Constraining neutral fraction How to distinguish internal absorption from IGM damping wing?? Using 050904: fHI < 0.6 (2-sigma) by fitting both DLA and IGM profiles GRBs as Probes of Reionization Damping wing? GRB050904 Kawai et al. 2005

  12. What Ionized the Universe? AGNs or Galaxies Reionization Budget • Depends on: • Luminosity density: • Detailed LF and IMF • Escape fraction of ionizing photons to the IGM: • Quasar: fesc~1 • Galaxies?? • Clumpiness of the IGM • Can quasars do it? Not likely • Too few quasars unless QLF remains to be steep to AGN luminosity • Extra constraints from X-ray background SFR of galaxies Density of quasars

  13. Reionization by stellar sources? • Large uncertainties in reionization photon budget: • IGM clumpiness; IMF; escape efficiency • Large cosmic (sample) variance in deep field data • Galaxy luminosity function at high-z • Sources of reionization have not been identified! • Most likely dwarf galaxies Necessary for reionization 6<z<9 (Stiavelli et al 2003) Bouwens & Illingworth; Bunker et al. ; Gnedin Yan and Windhorst

  14. Probing Reionization History Fan, Carilli & Keating 2006

  15. Quest to the Highest Redshift

  16. Next Generation Quasar Surveys • Optical surveys: limited to z<7 • New generations of red-sensitive CCD devices • Improved QE at 1 micron (Y band) • SUBARU/Princeton (2010+): a few hundred deg, Y<25;? • Pan-Starrs (2008+): 3: Y<22.5; 1000 deg2: Y<24; 30 deg2: Y<26 • LSST (2013+): 3: Y< 25 • Discovery of large number of quasars at z<7.5 • New generation of Near-IR surveys: • UKIDSS (2005 - 2012?): 4000 deg2: JAB<21 • VISTA/VHS (2008+): 20000 deg2: JAB<21 • VISTA/VIKING (2008+): 1500 deg2: JAB<22 • VISTA/VIDEO (2008+): 15 deg2: JAB<24.5 • Discovery of a handful of quasars at z=7-9

  17. Measuring G-P optical depth R~100 mode for faint AGNs Insensitive to neutral era Measuring HII region sizes R~1000 mode Sensitive to high fHI Radiative transfer effects causing large scatter for individual object Modest S/N but require large sample JAB<24.5 (deep surveys) Probing reionization using dark gap distribution: R~2700 mode Sensitive to overlap topology JAB<22.5 (wide surveys!) Probing the Neutral Era with JWST Quasar Spectroscopy JWST/NIRspec 300k sec

  18. Evolution of IGM Metals Evolution of CIV systems • Early Enrichment of the IGM by First stars • Lack of evolution in metal line density up to z~6 • OI Forest (Oh 2002) • OI and H have almost identical ionization potentials • In charge exchange equilibrium with H but much lower abundance • Fluctuating OI forest during neutral era to probe ionization topology and metal pollution in the IGM Ryan-Weber et al. OI system at z=6.26 Becker et al. 2006

  19. Will there be enough quasars? • For z>9 (assuming quasar LF evolution has not steepened) • Bright (AB<22.5): 0.2/100 deg2 • Faint (AB<24.5): 1-10/100 deg2 • difficult for current or planned ground-based IR surveys to find enough quasars for JWST reionization probes… Number expected Based on z~6 QLF

  20. Spitzer Warm Mission Survey? • Wide-field IRAC survey as path-finder to JWST (Gardner, XF, Wilson, Stiavelli) • 500 deg2 to SWIRE depth • Combined with deep optical/near-IR data for selection

  21. 4yr eROSITA ½yr e-ROSITA • All sky X-ray survey • PI. G. Hasinger • Launch 2011 • Expect: • 60 quasars at z>7 • 20 at z>8 • 5 at z>9

  22. Lyman  Emitter at z~10? • Keck blind spectroscopic survey along critical lines of high-z clusters • Six promising Ly emitter candidates at z=8.7 - 10.2 • Large abundance of low-L galaxies; providing sufficient reionization photons • Limit of ground-based search; extremely difficult to confirm spectroscopically Stark, Ellis et al.

  23. Ground-based Ly  surveys • DAZEL - The Dark Age Z(redshift) Lyman- Explorer on VLT: • dedicated Ly  narrow band survey instrument for z=7 - 10 • ~ 1 object per 10 hour field • New generation of OH suppression technique and AO: • Ground-based surveys could find Ly  emitters at z<12 McMahon et al. Bland-Hawthorn J H K

  24. Reionization Topology with Ly Emitters • Ly  emitter could provide sensitive probe to reionization history, especially during overlapping • Evolution of LF (constrain fHI) • Clustering • genus numbers Distribution of Ly emitters over JWST FOV Neutral  Ionized Angular correlation of Ly emitters McQuinn et al.

  25. Ly Emitter Surveys in JWST Era intrinsic observed • Interpretation of Ly emitters alone is highly model dependent: • Evolution of continuum LF • Uncertainties in Ly radiative transfer • Intrinsic clustering of galaxies etc. • Requires surveys of continuum and SF selected samples • Ly selected  continuum selected Rhoads 2007

  26. Synergetic survey of galaxies in reionization era FGS/TFI NIRSpec

  27. Synergetic Survey of Galaxies in Reionization Era • JWST will detect sources that reionization the Universe at z>10 • Ability to find high-z sources limited by whether the Universe managed to make them • Ground-based and JWST/TFI will detect Ly and HeII emitters to probe reionization history and topology • ALMA will provide dust/star-formation/dynamics Windhorst et al.

  28. Wish List to Theorists • Reionization Simulation • Volume: hundreds of Mpc • Resolution: dwarf galaxy halos and Lyman Limit Systems • Radiative transfer • Star formation prescriptions • Contribution from Pop III • Ly emission physics • Understanding escape fraction of ionization photons Gnedin and Fan 2006

  29. Escape Fraction: A Key Uncertainty • Escape fraction (as a function of z, L, age) affects: • Total reionization budget • HII region sizes • Ly emitter probe • Current measurements extremely uncertain • Shapley et al. at z~3: 2/14 detections • Siana et al. at z~1: fesc <0.02; evolution? • Large HST surveys underway • But how to measure it at z>6??? Siana et al. 2007

  30. Summary • What do we know now about reionization? • zrei = 6 - 13 • Overlapping probably late with extended reionization process • AGN not likely sources of reionization; situation for galaxies uncertain • What do we expect to know before JWST • Reionization history to z~8 from quasars/GRBs • Needs more powerful quasar surveys (Spitzer warm and eROSITA) • Small number of Ly emitters at z=7 - 10 • Lyman break-selected population at z~8-10 from WFC3: better constraints on reionization budget • Progress in reionization simulations • Roles of JWST • Absorption line probes using high-z quasars • Identify the reionization population • Mapping out Ly emitters at the peak of reionization, synergy with ALMA and GSMT/ELT

  31. Probing Reionization History JWST, GSMT 21cm, GRB, ALMA Fan, Carilli, Keating 2006

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