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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

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
Outline

  • Reionization on a Global Level

    • Assumptions

    • Feedback

  • Inhomogeneous Reionization

    • Early Phases

    • Late Phases

  • Observational Prospects


Simple reionization models ingredients
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 ingredients1
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
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
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
The Global 21 cm Signal

Pop II Stars

Pop III Stars

SF (in prep)


Inhomogeneous reionization
Inhomogeneous Reionization

z=18.3

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization1
Inhomogeneous Reionization

z=16.1

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization2
Inhomogeneous Reionization

z=14.5

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization3
Inhomogeneous Reionization

z=13.2

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization4
Inhomogeneous Reionization

z=12.1

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization5
Inhomogeneous Reionization

z=11.2

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization6
Inhomogeneous Reionization

z=10.4

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization7
Inhomogeneous Reionization

z=9.8

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization8
Inhomogeneous Reionization

z=9.2

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization9
Inhomogeneous Reionization

z=8.7

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization10
Inhomogeneous Reionization

z=8.3

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization11
Inhomogeneous Reionization

z=7.9

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization12
Inhomogeneous Reionization

z=7.5

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Inhomogeneous reionization13
Inhomogeneous Reionization

z=9.2

13 Mpc comoving

Dn=0.1 MHz

SF, AS, LH (2004)


Photon counting
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 counting1
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 counting2
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 counting3
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
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 sizes1
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
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: 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

  • 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
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
Much Ado About Clumping

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

Ionized IGM

Neutral IGM


Much ado about clumping1
Much Ado About Clumping

Ionized IGM

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

Neutral IGM


Much ado about clumping2
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 clumping3
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
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
Overlap and Phase Transitions

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

Gnedin (2000)


The hidden meaning of overlap
The Hidden Meaning of Overlap

Without recombinations

Rmax

Box Size

SF, SPO (2005)

Gnedin (2000)


Fuzzy overlap
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 clumping4
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 clumping5
Much Ado About Clumping

  • Assuming ionizing sources are clustered: thick lines

    • Spatially variable

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

SF, SPO (2005)


Reionization observables
Reionization Observables

  • The 21 cm Sky

  • CMB Temperature Anisotropies

  • Ly Emitters

  • Quasar (or GRB) Spectra


The 21 cm power spectrum
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


Ly a emitters and hii regions

Total optical depth in Ly transition:

Damping wings are strong

See many later talks!

Lya Emitters and HII Regions

IGM HI


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 large scales1

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
Clustering on Small Scales

  • Nearly randomly distributed galaxy population

  • Small bubble: too much extinction, disappears

  • Large bubble: galaxies visible to survey


Clustering on small scales1
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 scales2
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
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
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
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 spectra1
Quasar Spectra

  • But complications!

    • Aliasing (Kaiser & Peacock 1991)

High-k mode

Line of sight


Quasar spectra2
Quasar Spectra

  • But complications!

    • Aliasing (Kaiser & Peacock 1991)

    • Transmission bias because only see through rare voids


Quasar spectra3
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
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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