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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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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


Outline

  • Reionization on a Global Level

    • Assumptions

    • Feedback

  • Inhomogeneous Reionization

    • Early Phases

    • Late Phases

  • Observational Prospects


Simple Reionization Models: Ingredients

  • Source Term:

    • Identify sources

    • Assign f*

    • Assign IMF

    • Assign fesc

  • Sink Term:

    •  ne nH C

Sokasian et al. (2003)


Simple Reionization Models: Ingredients

  • Source Term:

    • Identify sources

    • Assign f*

    • Assign IMF

    • Assign fesc

  • Sink Term:

    •  ne nH C

  • Doesn’t fit WMAP+SDSS


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)


Reionization Models:Feedback II

  • Pop III/Pop II transition

    • IGM Enrichment

    • Clustering

    • ISM Enrichment

    • Gradual?

  • See Cen’s talk later on

SF, AL (2005)


The Global 21 cm Signal

Pop II Stars

Pop III Stars

SF (in prep)


Inhomogeneous Reionization

z=18.3

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=16.1

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=14.5

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=13.2

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=12.1

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=11.2

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=10.4

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=9.8

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=9.2

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=8.7

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=8.3

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=7.9

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=7.5

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous Reionization

z=9.2

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


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


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


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


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


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)


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)


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)


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)


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)


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)


Much Ado About Clumping

  • For bubble to grow, ionizing photons must reach bubble wall

Ionized IGM

Neutral IGM


Much Ado About Clumping

Ionized IGM

  • Mean free path must exceed Rbub larger bubbles must ionize blobs more deeply

Neutral IGM


Much Ado About Clumping

Ionized IGM

  • Outskirts of blobs contain densest ionized gas  recombination rate increases with mean free path

Neutral IGM


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


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)


Overlap and Phase Transitions

  • In simulations, reionization appears to be an extremely rapid global phase transition

Gnedin (2000)


The Hidden Meaning of Overlap

Without recombinations

Rmax

Box Size

SF, SPO (2005)

Gnedin (2000)


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)


Much Ado About Clumping

  • Assuming uniform ionizing flux: C>30 (Gnedin & Ostriker 1997)

  • Assuming voids ionized first: thin lines (MHR00)

SF, SPO (2005)


Much Ado About Clumping

  • Assuming ionizing sources are clustered: thick lines

    • Spatially variable

    • Depends on P() AND bubble model!!!

SF, SPO (2005)


Reionization Observables

  • The 21 cm Sky

  • CMB Temperature Anisotropies

  • Ly Emitters

  • Quasar (or GRB) Spectra


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


Total optical depth in Ly transition:

Damping wings are strong

See many later talks!

Lya Emitters and HII Regions

IGM HI


Large scales:

Galaxies in separate bubbles  depends on clustering of bubbles

Large bubbles are rare density peaks: highly clustered

Clustering on Large Scales


Large scales:

Galaxies in separate bubbles  depends on clustering of bubbles

Large bubbles are rare density peaks: highly clustered

Clustering on Large Scales


Clustering on Small Scales

  • Nearly randomly distributed galaxy population

  • Small bubble: too much extinction, disappears

  • Large bubble: galaxies visible to survey


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


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


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)


Secondary CMB Anisotropies

  • Nonlinear kinetic Sunyaev-Zeldovich and “Patchy Reionization” signals

  • Especially large for extended reionization

Total

Patchy

103

104

McQuinn et al. (2005)


Quasar Spectra

  • SDSS J1030 (z=6.28)

    • No flux for z=6.2-5.98

  • SDSS J1148 (z=6.42)

    • Residual Flux! (White et al. 2005, Oh & Furlanetto 2005)

  • A signature of reionization? (Wyithe & Loeb 2005, Fan et al. 2006)

White et al. (2003)


Quasar Spectra

  • But complications!

    • Aliasing (Kaiser & Peacock 1991)

High-k mode

Line of sight


Quasar Spectra

  • But complications!

    • Aliasing (Kaiser & Peacock 1991)

    • Transmission bias because only see through rare voids


Quasar Spectra

  • Observed variance slightly more than expected from uniform ionizing background

    • Structure in intrinsic quasar spectra is likely another significant contributor

  • Difficult but possible!

Smoothing length=40 Mpc/h

Lidz, Oh, & Furlanetto (2006)


Conclusions

  • Models of global reionization history subject to uncertainties about parameters

    • Feedback especially difficult!

  • Inhomogeneous Reionization

    • Early phases: photon counting

    • Late phases: recombinations

  • A number of observational opportunities ahead!


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