The twilight zone of reionization
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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 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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