the twilight zone of reionization

The Twilight Zoneof Reionization

The Twilight Zoneof Reionization

Steve Furlanetto

Yale University

March 13, 2006

Steve Furlanetto

Yale University

March 13, 2006Collaborators: F. Briggs, L. Hernquist, A. Lidz, A. Loeb,

M. McQuinn, S.P. Oh, J. Pritchard, A. Sokasian, O. Zahn, M. Zaldarriaga

OutlineOutline

Reionization on a Global Level Assumptions Feedback

Inhomogeneous Reionization Early Phases Late Phases

Observational Prospects

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



Sink Term: ne nH C

Sokasian et al. (2003)





Sink Term: ne nH C

Doesn’t fit WMAP+SDSS



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)

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

Pop III/Pop II transition IGM Enrichment Clustering ISM Enrichment Gradual?

See Cen’s talk later on

SF, AL (2005)

The Global 21 cm SignalThe Global 21 cm Signal

SF (in prep)

Pop II Stars Pop III Stars

Inhomogeneous ReionizationInhomogeneous Reionization

z=18.3z=18.3

13 Mpc comoving13 Mpc comoving

=0.1 MHz=0.1 MHz

SF, AS, LH (2004)SF, AS, LH (2004)

z=16.1z=16.1

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=14.5z=14.5

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=13.2z=13.2

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=12.1z=12.1

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=11.2z=11.2

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=10.4z=10.4

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=9.8z=9.8

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=9.2z=9.2

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=8.7z=8.7

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=8.3z=8.3

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=7.9z=7.9

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=7.5z=7.5

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


z=9.2z=9.2

=0.1 MHz=0.1 MHz


SF, AS, LH (2004)SF, AS, LH (2004)


Photon CountingPhoton Counting

Simple ansatz:

mion = mgal

= f* fesc N/b / (1+nrec)

Then condition for a region to be fully ionized is

fcoll > -1

Simple ansatz:

mion = mgal



fcoll > -1

Neutral IGM

Ionized IGM

Galaxy


Simple ansatz:

mion = mgal



fcoll > -1

Simple ansatz:

mion = mgal



fcoll > -1

Neutral IGM

Ionized IGM?

Galaxy


Simple ansatz:

mion = mgal

= f* fesc N/b / (1+nrec) Then condition for a

region to be fully ionized is

fcoll > -1

Can construct an analog of Press-Schechter mass function = mass function of ionized regions

Simple ansatz:

mion = mgal

= f* fesc N/b / (1+nrec) Then condition for a

region to be fully ionized is

fcoll > -1

Can construct an analog of Press-Schechter mass function = mass function of ionized regions

Neutral IGM

Ionized IGM

Galaxy

SF, MZ, LH (2004a)SF, MZ, LH (2004a)

=40xH=0.96

xH=0.70

xH=0.25

Bubble SizesBubble Sizes

Bubbles are BIG!!! Many times the size of

each galaxy’s HII region

2 Mpc = 1 arcmin Much larger than

simulation boxes

Bubbles are BIG!!! Many times the size of

each galaxy’s HII region

2 Mpc = 1 arcmin Much larger than

simulation boxes

Typical galaxy bubble

SF, MZ, LH (2004a)SF, MZ, LH (2004a)

=40xH=0.96

xH=0.70xH=0.25

Bubble SizesBubble Sizes

Bubbles are BIG!!! Have characteristic

size Scale at which typical

density fluctuation is enough to ionize region

Galaxy bias gives a boost!


size Scale at which typical

density fluctuation is enough to ionize region

Galaxy bias gives a boost!

€

σ(R) ≈ δx

The Characteristic Bubble SizeThe Characteristic Bubble Size


size Depends primarily on

the bias of ionizing sources


size Depends primarily on

the bias of ionizing sources

xH=0.84

xH=0.025

SF, MM, LH (2005)SF, MM, LH (2005)

xH=0.35

€

fcoll ≈ ζ f coll (1+ bδ) >1

SF, MM, LH (2005)SF, MM, LH (2005)

Bubbles: Redshift DependenceBubbles: Redshift Dependence


size Sizes independent of

z (for a fixed xH)



z (for a fixed xH)

xH=0.84

xH=0.025

xH=0.35

SF, MM, LH (2005)SF, MM, LH (2005)

BubblesBubbles



z (for a fixed xH) It works! See

McQuinn talk and poster



z (for a fixed xH) It works! See

McQuinn talk and poster

xH=0.84

xH=0.025

xH=0.35

SF, MM, LH (2005)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)

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=0.84

xH=0.025

xH=0.35

Much Ado About ClumpingMuch Ado About Clumping

For bubble to grow, ionizing photons must reach bubble wall

For bubble to grow, ionizing photons must reach bubble wall

Neutral IGM

Ionized IGM


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

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

Neutral IGM

Ionized IGM


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

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

Neutral IGM

Ionized IGM


Growing bubble thus requires ion rate > recombination rate (see also Miralda-Escude et al. 2000)

Clumping factor is model-dependent!!!

Growing bubble thus requires ion rate > recombination rate (see also Miralda-Escude et al. 2000)

Clumping factor is model-dependent!!!

Neutral IGM

Ionized IGM

€

dfcoll

dt> AuC(R,δ)

SF, SPO (2005)SF, SPO (2005)

xH=0.49

xH=0.32

xH=0.08

Bubbles and RecombinationsBubbles and Recombinations

Recombinations impose saturation radius Rmax

Rmax limit depends on… Density structure of

IGM Emissivity (rate of

collapse)

Recombinations impose saturation radius Rmax

Rmax limit depends on… Density structure of

IGM Emissivity (rate of

collapse)

xH=0.16

Overlap and Phase TransitionsOverlap and Phase Transitions

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

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

Gnedin (2000)Gnedin (2000)

The Hidden Meaning of OverlapThe Hidden Meaning of Overlap

Gnedin (2000)Gnedin (2000)

Box Size

SF, SPO (2005)SF, SPO (2005)

Rmax

Without recombinations

Fuzzy OverlapFuzzy Overlap

For any point, overlap is complete when bubble growth saturates

Gives reionization an intrinsic width!!! Constrains density

structure Quasars show z~0.3

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)SF, SPO (2005)


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

Assuming voids ionized first: thin lines (MHR00)

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

Assuming voids ionized first: thin lines (MHR00)

SF, SPO (2005)SF, SPO (2005)


Assuming ionizing sources are clustered: thick lines Spatially variable Depends on P() AND

bubble model!!!

Assuming ionizing sources are clustered: thick lines Spatially variable Depends on P() AND

bubble model!!!

SF, SPO (2005)SF, SPO (2005)

Reionization ObservablesReionization Observables

The 21 cm Sky CMB Temperature Anisotropies Ly Emitters Quasar (or GRB) Spectra

The 21 cm Sky CMB Temperature Anisotropies Ly Emitters Quasar (or GRB) Spectra

The 21 cm Power SpectrumThe 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

Model allows us to compute statistical properties of signal

Rich set of information from bubble distribution (timing, feedback, sources, etc.)

Full 3D dataset

xi=0.78

z=10

xi=0.13

xi=0.36xi=0.48

xi=0.59

xi=0.69

Ly Emitters and HII RegionsLy Emitters and HII Regions

Total optical depth in Ly transition:

Damping wings are strong

See many later talks!

Total optical depth in Ly transition:

Damping wings are strong

See many later talks!

IGM HI

€

τGP ≈ 3x105 xHI

1+ z

7

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⎝ ⎜

⎞

⎠ ⎟3 / 2

Clustering on Large ScalesClustering on Large Scales

Large scales: Galaxies in separate

bubbles depends on clustering of bubbles

Large bubbles are rare density peaks: highly clustered

Large scales: Galaxies in separate

bubbles depends on clustering of bubbles

Large bubbles are rare density peaks: highly clustered

Clustering on Small ScalesClustering on Small Scales

Nearly randomly distributed galaxy population

Small bubble: too much extinction, disappears

Large bubble: galaxies visible to survey

Nearly randomly distributed galaxy population



Clustering on Small ScalesClustering on Small Scales



Absorption selects large bubbles, which tend to surround clumps of galaxies



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

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 AnisotropiesSecondary CMB Anisotropies

Nonlinear kinetic Sunyaev-Zeldovich and “Patchy Reionization” signals

Especially large for extended reionization

Nonlinear kinetic Sunyaev-Zeldovich and “Patchy Reionization” signals

Especially large for extended reionization

McQuinn et al. (2005)

Total

104103

Patchy

Quasar SpectraQuasar 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)

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)


But complications! Aliasing (Kaiser &

Peacock 1991)


Peacock 1991)

High-k mode

Line of sight



Peacock 1991) Transmission bias

because only see through rare voids


Peacock 1991) Transmission bias

because only see through rare voids


Observed variance slightly more than expected from uniform ionizing background Structure in intrinsic

quasar spectra is likely another significant contributor

Difficult but possible!

Observed variance slightly more than expected from uniform ionizing background Structure in intrinsic

quasar spectra is likely another significant contributor

Difficult but possible!Lidz, Oh, & Furlanetto (2006)

Smoothing length=40 Mpc/h

ConclusionsConclusions

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!

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!

the twilight zone of reionization

Documents

mhz13 mpc comovingsf

mpc comovingdn

z mgalz

ionized isfcoll z

galaxys hii region2

sourcesassign f

fesc ngb

nrecthen condition