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The Twilight Zone of Reionization

The Twilight Zone of Reionization. Steve Furlanetto Yale University March 13, 2006. Collaborators: F. Briggs, L. Hernquist, A. Lidz, A. Loeb, M. McQuinn, S.P. Oh, J. Pritchard, A. Sokasian, O. Zahn, M. Zaldarriaga. Outline. Reionization on a Global Level Assumptions Feedback

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The Twilight Zone of Reionization

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  1. The Twilight Zoneof Reionization Steve Furlanetto Yale University March 13, 2006 Collaborators: F. Briggs, L. Hernquist, A. Lidz, A. Loeb, M. McQuinn, S.P. Oh, J. Pritchard, A. Sokasian, O. Zahn, M. Zaldarriaga

  2. Outline • Reionization on a Global Level • Assumptions • Feedback • Inhomogeneous Reionization • Early Phases • Late Phases • Observational Prospects

  3. Simple Reionization Models: Ingredients • Source Term: • Identify sources • Assign f* • Assign IMF • Assign fesc • Sink Term: •  ne nH C Sokasian et al. (2003)

  4. Simple Reionization Models: Ingredients • Source Term: • Identify sources • Assign f* • Assign IMF • Assign fesc • Sink Term: •  ne nH C • Doesn’t fit WMAP+SDSS

  5. Reionization Models: Feedback I • Any or all parameters may evolve! • Photoheating • Metallicity • H2 cooling • Feedback on clumping • Double reionization difficult to arrange (SF, AL 2005)

  6. Reionization Models:Feedback II • Pop III/Pop II transition • IGM Enrichment • Clustering • ISM Enrichment • Gradual? • See Cen’s talk later on SF, AL (2005)

  7. The Global 21 cm Signal Pop II Stars Pop III Stars SF (in prep)

  8. Inhomogeneous Reionization z=18.3 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  9. Inhomogeneous Reionization z=16.1 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  10. Inhomogeneous Reionization z=14.5 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  11. Inhomogeneous Reionization z=13.2 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  12. Inhomogeneous Reionization z=12.1 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  13. Inhomogeneous Reionization z=11.2 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  14. Inhomogeneous Reionization z=10.4 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  15. Inhomogeneous Reionization z=9.8 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  16. Inhomogeneous Reionization z=9.2 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  17. Inhomogeneous Reionization z=8.7 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  18. Inhomogeneous Reionization z=8.3 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  19. Inhomogeneous Reionization z=7.9 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  20. Inhomogeneous Reionization z=7.5 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  21. Inhomogeneous Reionization z=9.2 13 Mpc comoving Dn=0.1 MHz SF, AS, LH (2004)

  22. Photon Counting • Simple ansatz: mion = z mgal z = f* fesc Ng/b / (1+nrec) • Then condition for a region to be fully ionized is fcoll > z-1 Ionized IGM Galaxy Neutral IGM

  23. Photon Counting • Simple ansatz: mion = z mgal z = f* fesc Ng/b / (1+nrec) • Then condition for a region to be fully ionized is fcoll > z-1 Ionized IGM Galaxy Neutral IGM

  24. Photon Counting • Simple ansatz: mion = z mgal z = f* fesc Ng/b / (1+nrec) • Then condition for a region to be fully ionized is fcoll > z-1 Ionized IGM? Galaxy Neutral IGM

  25. Photon Counting • Simple ansatz: mion = z mgal z = f* fesc Ng/b / (1+nrec) • Then condition for a region to be fully ionized is fcoll > z-1 • Can construct an analog of Press-Schechter mass function = mass function of ionized regions Ionized IGM Galaxy Neutral IGM

  26. Bubble Sizes Typical galaxy bubble • Bubbles are BIG!!! • Many times the size of each galaxy’s HII region • 2 Mpc = 1 arcmin • Much larger than simulation boxes xH=0.96 z=40 xH=0.70 xH=0.25 SF, MZ, LH (2004a)

  27. Bubble Sizes • Bubbles are BIG!!! • Have characteristic size • Scale at which typical density fluctuation is enough to ionize region • Galaxy bias gives a boost! xH=0.96 z=40 xH=0.70 xH=0.25 SF, MZ, LH (2004a)

  28. The Characteristic Bubble Size • Bubbles are BIG!!! • Have characteristic size • Depends primarily on the bias of ionizing sources xH=0.025 xH=0.35 xH=0.84 SF, MM, LH (2005)

  29. Bubbles: Redshift Dependence • Bubbles are BIG!!! • Have characteristic size • Sizes independent of z (for a fixed xH) xH=0.025 xH=0.35 xH=0.84 SF, MM, LH (2005)

  30. Bubbles • Bubbles are BIG!!! • Have characteristic size • Sizes independent of z (for a fixed xH) • It works! See McQuinn talk and poster xH=0.025 xH=0.35 xH=0.84 SF, MM, LH (2005)

  31. A Curious Result… • FZH04 bubbles grow to be infinitely large! • What do we mean by a “bubble”? • Full extent of ionized gas? (Wyithe & Loeb 2004) • Mean free path of ionizing photon? (SF, SPO 2005) xH=0.025 xH=0.35 xH=0.84 SF, MM, LH (2005)

  32. Much Ado About Clumping • For bubble to grow, ionizing photons must reach bubble wall Ionized IGM Neutral IGM

  33. Much Ado About Clumping Ionized IGM • Mean free path must exceed Rbub larger bubbles must ionize blobs more deeply Neutral IGM

  34. Much Ado About Clumping Ionized IGM • Outskirts of blobs contain densest ionized gas  recombination rate increases with mean free path Neutral IGM

  35. Much Ado About Clumping Ionized IGM • Growing bubble thus requires ion rate > recombination rate (see also Miralda-Escude et al. 2000) • Clumping factor is model-dependent!!! Neutral IGM

  36. Bubbles and Recombinations • Recombinations impose saturation radius Rmax • Rmax limit depends on… • Density structure of IGM • Emissivity (rate of collapse) xH=0.16 xH=0.32 xH=0.08 xH=0.49 SF, SPO (2005)

  37. Overlap and Phase Transitions • In simulations, reionization appears to be an extremely rapid global phase transition Gnedin (2000)

  38. The Hidden Meaning of Overlap Without recombinations Rmax Box Size SF, SPO (2005) Gnedin (2000)

  39. Fuzzy Overlap • For any point, overlap is complete when bubble growth saturates • Gives reionization an intrinsic width!!! • Constrains density structure • Quasars show z~0.3 SF, SPO (2005)

  40. Much Ado About Clumping • Assuming uniform ionizing flux: C>30 (Gnedin & Ostriker 1997) • Assuming voids ionized first: thin lines (MHR00) SF, SPO (2005)

  41. Much Ado About Clumping • Assuming ionizing sources are clustered: thick lines • Spatially variable • Depends on P() AND bubble model!!! SF, SPO (2005)

  42. Reionization Observables • The 21 cm Sky • CMB Temperature Anisotropies • Ly Emitters • Quasar (or GRB) Spectra

  43. The 21 cm Power Spectrum • Model allows us to compute statistical properties of signal • Rich set of information from bubble distribution (timing, feedback, sources, etc.) • Full 3D dataset xi=0.59 xi=0.78 xi=0.69 xi=0.48 xi=0.36 xi=0.13 z=10

  44. Total optical depth in Ly transition: Damping wings are strong See many later talks! Lya Emitters and HII Regions IGM HI

  45. Large scales: Galaxies in separate bubbles  depends on clustering of bubbles Large bubbles are rare density peaks: highly clustered Clustering on Large Scales

  46. Large scales: Galaxies in separate bubbles  depends on clustering of bubbles Large bubbles are rare density peaks: highly clustered Clustering on Large Scales

  47. Clustering on Small Scales • Nearly randomly distributed galaxy population • Small bubble: too much extinction, disappears • Large bubble: galaxies visible to survey

  48. Clustering on Small Scales • Small bubble: too much extinction, disappears • Large bubble: galaxies visible to survey • Absorption selects large bubbles, which tend to surround clumps of galaxies

  49. Clustering on Small Scales • Small bubble: too much extinction, disappears • Large bubble: galaxies visible to survey • Absorption selects large bubbles, which tend to surround clumps of galaxies

  50. The Evolving Correlation Function • Top panel: Small scale bias bsm • Middle panel: Large scale bias b(infinity) • Bottom panel: Ratio of the two • Crossover scale is Rchar SF, MZ, LH (2005)

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