the topology of reionization

The Topology of Reionization

Dr. Steven Furlanetto, Caltech (KITP Galaxy-IGM Program 12/07/04) 1

The Topology of ReionizationThe Topology of Reionization

Steve FurlanettoDecember 7, 2004Steve Furlanetto

December 7, 2004

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OutlineOutline

� Introduction� Topology� Observational Probes

� QSO spectra� Lyα galaxies� Secondary CMB anisotropies� 21 cm tomography

� The Mileura Widefield Array

� Introduction� Topology� Observational Probes

� QSO spectra� Lyα galaxies� Secondary CMB anisotropies� 21 cm tomography

� The Mileura Widefield Array



What Is Reionization?What Is Reionization?

� Why is it interesting?� Hallmark event of first sources� Measures interaction with IGM� Affects z=0 objects

� What do we expect?� Rapid phase transition� z~6-20

� What do we want to know?� When?� Why?

� How?

� Why is it interesting?� Hallmark event of first sources� Measures interaction with IGM� Affects z=0 objects

� What do we expect?� Rapid phase transition� z~6-20

� What do we want to know?� When?� Why?

� How?

Sokasian et al. (2003)

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Comparing the ObservationsComparing the Observations

� WMAP: begins at z>14� Lya forest temperature: z<10� Lya emitters: mostly ionized at

z=6.5� GP trough: changing rapidly at

z=6.1, variability� QSO proximity zones: partly

neutral at z=6.3� Together imply complex time

history!

� WMAP: begins at z>14� Lya forest temperature: z<10� Lya emitters: mostly ionized at

z=6.5� GP trough: changing rapidly at

z=6.1, variability� QSO proximity zones: partly

neutral at z=6.3� Together imply complex time

history!

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GP Trough

Temperature

WMAP

Lyαααα Gals

Proximity Zones




� Simple semi-analytic models treat HII regions around individual galaxies

� Clustered sources� Large HII regions

� Consistent with simulations and analytic work (Barkana & Loeb 2004)

� Simple semi-analytic models treat HII regions around individual galaxies

� Clustered sources� Large HII regions

� Consistent with simulations and analytic work (Barkana & Loeb 2004)

Sokasian et al. (2003)

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Real Inhomogeneity!Real Inhomogeneity!

� SDSS J1030 (z=6.28)� No flux at z=6.2-5.98 in

either Lyα or Lyβ� τα>9.9 (2σ; mean effective

value)

� SDSS J1148 (z=6.42)� Transmission spikes in

Lyα, Lyβ troughs� Residual flux elsewhere� τα < 14.3 (2σ), likely τα~6-

10 (from clean Lyγ trough; Oh & Furlanetto 2004)

� SDSS J1030 (z=6.28)� No flux at z=6.2-5.98 in

either Lyα or Lyβ� τα>9.9 (2σ; mean effective

value)

� SDSS J1148 (z=6.42)� Transmission spikes in

Lyα, Lyβ troughs� Residual flux elsewhere� τα < 14.3 (2σ), likely τα~6-

10 (from clean Lyγ trough; Oh & Furlanetto 2004)

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� Simple ansatz:

mion = ζ mgal

ζ = f* fesc Nγ/b / (1+nrec)

� Then condition for a region to be fully ionized is

fcoll > ζ-1

� Simple ansatz:

mion = ζ mgal



fcoll > ζ-1

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� Simple ansatz:

mion = ζ mgal



fcoll > ζ-1

� Simple ansatz:

mion = ζ mgal



fcoll > ζ-1

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� Simple ansatz:

mion = ζ mgal



fcoll > ζ-1

� Simple ansatz:

mion = ζ mgal



fcoll > ζ-1

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� Simple ansatz:mion = ζ mgal



fcoll > ζ-1

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

� Simple ansatz:mion = ζ mgal



fcoll > ζ-1

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

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� Large bubbles � easy to observe




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� Characteristic size �easy to observe



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� Trust no one!!!



� Trust no one!!!




� Mostly independent of redshift at fixed xH

� Depends primarily on the bias of ionizing sources

� Solid lines: f*=const� Dashed lines: f*~m2/3

� Other factors…� Clumping/recombinations� Bursty star formation� Feedback!

� Mostly independent of redshift at fixed xH

� Depends primarily on the bias of ionizing sources

� Solid lines: f*=const� Dashed lines: f*~m2/3

� Other factors…� Clumping/recombinations� Bursty star formation� Feedback!

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Observational ProbesObservational Probes

� Quasar/GRB spectra

� Lyα Emitters� Secondary CMB Anisotropies� Redshifted 21 cm emission

� Quasar/GRB spectra

� Lyα Emitters� Secondary CMB Anisotropies� Redshifted 21 cm emission



QSO/GRB SpectraQSO/GRB Spectra

� Transmission spike at z=6.08 appears in both Lyα and Lyβ: real even if you accept interloper

� Lyβ spikes also (probably) real (Oh & Furlanetto 2004)� What do they tell us???

� Transmission spike at z=6.08 appears in both Lyα and Lyβ: real even if you accept interloper

� Lyβ spikes also (probably) real (Oh & Furlanetto 2004)� What do they tell us???

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Transmission SpikesTransmission Spikes

� For transmission:� Must eliminate resonant

absorption: pass close to ionizing source

� Must eliminate damping wing absorption: pass through large HII region

� For isolated galaxies, NO features before reionization (Barkana 2002)

� For transmission:� Must eliminate resonant

absorption: pass close to ionizing source

� Must eliminate damping wing absorption: pass through large HII region

� For isolated galaxies, NO features before reionization (Barkana 2002) IGM HI

QSO

QSO



QSO Absorption SpectraQSO Absorption Spectra

� Include clustering of sources: eliminate damping wing absorption

� Curves have xH=(0.1,0.15,0.2,0.25) at z=6.1

� Simple model: � Includes inhomogeneous IGM� Naïve distribution of sources

within bubbles� No recombinations

� Spectra during/after reionization need MUCH better modeling (Oh & Furlanetto 2004)

� Include clustering of sources: eliminate damping wing absorption

� Curves have xH=(0.1,0.15,0.2,0.25) at z=6.1

� Simple model: � Includes inhomogeneous IGM� Naïve distribution of sources

within bubbles� No recombinations

� Spectra during/after reionization need MUCH better modeling (Oh & Furlanetto 2004)

SF, LH, MZ (2004)

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Lyα Emitters and TopologyLyα Emitters and Topology

� Total optical depth in Lyαtransition:

� “Damping wing” absorption from neutral IGM� Depends on distance to edge of

HII region

� “Resonant absorption” from gas inside the HII region� Determined by local ionizing flux

� Total optical depth in Lyαtransition:

� “Damping wing” absorption from neutral IGM� Depends on distance to edge of

HII region

� “Resonant absorption” from gas inside the HII region� Determined by local ionizing flux

IGM HI

HII region aroundsmall galaxy

HII region aroundclustered sources

τGP ≈ 6x105 xHI

1+ z

10

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Lyα Galaxy SurveysLyα Galaxy Surveys

� Resonant absorption determined by galaxy’s luminosity� Destroys blue side� Red side unaffected

� Damping wing absorption determined by size of HII region� 109 Msun galaxy at z=10 has

(75%, 40%, 20%, 3%) chance to be in HII regions larger than shown if xH=0.5

� Surveys can measure distribution of bubble sizes

� Resonant absorption determined by galaxy’s luminosity� Destroys blue side� Red side unaffected

� Damping wing absorption determined by size of HII region� 109 Msun galaxy at z=10 has

(75%, 40%, 20%, 3%) chance to be in HII regions larger than shown if xH=0.5

� Surveys can measure distribution of bubble sizes

SF, LH, MZ (2004)

The Evolving Luminosity Function

The Evolving Luminosity Function

� Intrinsic luminosity function depends on geometry, kinematics, dust, etc.

� But those factors (probably, more or less) constant with redshift

� Thick black line: post-reionization� Blue line: xH=0.25� Magenta line: xH=0.5� Red line: xH=0.75� Thin black line: ruled out by

Malhotra & Rhoads (2004)� Lyα galaxies should be visible

farther back into reionization epoch

� Intrinsic luminosity function depends on geometry, kinematics, dust, etc.

� But those factors (probably, more or less) constant with redshift

� Thick black line: post-reionization� Blue line: xH=0.25� Magenta line: xH=0.5� Red line: xH=0.75� Thin black line: ruled out by

Malhotra & Rhoads (2004)� Lyα galaxies should be visible

farther back into reionization epoch

SF, LH, MZ (in prep)



Secondary CMB AnisotropiesSecondary CMB Anisotropies

� Nonlinear kSZ (Ostriker-Vishniac)� Determined by nonlinear

structure formation� Depends slightly on

reionization redshift

� Patchy reionization (Gruzinov & Hu 1998; Knox et al. 1998; Santos et al. 2003)� Anisotropies from ionized

bubbles� Depends on bubble scale

� Nonlinear kSZ (Ostriker-Vishniac)� Determined by nonlinear

structure formation� Depends slightly on

reionization redshift

� Patchy reionization (Gruzinov & Hu 1998; Knox et al. 1998; Santos et al. 2003)� Anisotropies from ionized

bubbles� Depends on bubble scale

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Secondary CMB Anisotropies IISecondary CMB Anisotropies II

� Signal especially large for extended reionization� Patchiness persists

over long time interval� Little information about

source details

� Signal especially large for extended reionization� Patchiness persists

over long time interval� Little information about

source details

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21 cm Tomography21 cm Tomography

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The 21 cm SignalThe 21 cm Signal

� Observable quantity is brightness temperature� Diffuse IGM has (Madau et al. 1997)

� Depends on spin temperature TS=excitation temperature of 21 cm transition� Determined by CMB, collisions (inefficient), Lyα photons� During reionization, Ts>>TCMB is most plausible� In that case, nearly independent of temperature

� Observable quantity is brightness temperature� Diffuse IGM has (Madau et al. 1997)

� Depends on spin temperature TS=excitation temperature of 21 cm transition� Determined by CMB, collisions (inefficient), Lyα photons� During reionization, Ts>>TCMB is most plausible� In that case, nearly independent of temperature

δTb ≈ 23x HI (1+ δ) 1+ z

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Characterizing the Topology: The Power Spectrum

Characterizing the Topology: The Power Spectrum

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The Power SpectrumThe Power Spectrum

� Dotted: z=18, xH=0.96� Short-dashed: z=15, xH=0.81� Long-dashed: z=13, xH=0.52� Solid: z=12, xH=0.26

� Dotted: z=18, xH=0.96� Short-dashed: z=15, xH=0.81� Long-dashed: z=13, xH=0.52� Solid: z=12, xH=0.26

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xH=0.81� Solid blue: z=12, xH=0.26

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Other Statistical MeasuresOther Statistical Measures

� xH field is not gaussian �power spectrum only part of the story

� Can construct pixel distribution function in any model� Solid: fcoll model� Dashed: void model� Dotted: uniform ionization

� Qualitatively different distributions!

� xH field is not gaussian �power spectrum only part of the story

� Can construct pixel distribution function in any model� Solid: fcoll model� Dashed: void model� Dotted: uniform ionization

� Qualitatively different distributions!

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So Can It Be Done?So Can It Be Done?

� Primeval Structure Telescope� Begin full scale construction 2005

� Dedicated instrument

� VLA survey� Targeted at 192-200 MHz

� LOw Frequency ARray� 30-240 MHz

� Aims for “first light” in ~2007

� Mileura Widefield Array� Square Kilometer Array

� Next generation radio telescope

� Many years away: initial operations sometime around 2020

� Primeval Structure Telescope� Begin full scale construction 2005

� Dedicated instrument

� VLA survey� Targeted at 192-200 MHz

� LOw Frequency ARray� 30-240 MHz

� Aims for “first light” in ~2007

� Mileura Widefield Array� Square Kilometer Array

� Next generation radio telescope

� Many years away: initial operations sometime around 2020



Mileura Widefield ArrayMileura Widefield Array

� Low-frequency radio telescope in Western Australia

� First observations with demonstrator (Maude) planned for 2007

� Collaborators include MIT, Melbourne, CfA, ATNF + others (SF, Briggs, Carilli)

� Also transients, heliosphere

� Low-frequency radio telescope in Western Australia

� First observations with demonstrator (Maude) planned for 2007

� Collaborators include MIT, Melbourne, CfA, ATNF + others (SF, Briggs, Carilli)

� Also transients, heliosphere


� Instrument characteristics� Radio-quiet site� 500 16-element antennae

(8000 m2) in 1.5 km distribution

� Full cross-correlation of all 500 antennae

� 80-300 MHz (z<16)� Many (4+) MHz

instantaneous bandwidth at 8 kHz resolution

� 400-1000 square degree field of view

� Instrument characteristics� Radio-quiet site� 500 16-element antennae

(8000 m2) in 1.5 km distribution

� Full cross-correlation of all 500 antennae

� 80-300 MHz (z<16)� Many (4+) MHz

instantaneous bandwidth at 8 kHz resolution

� 400-1000 square degree field of view




� Instrument emphasizes:� Survey speed� Data quality� Calibration

� Simulated data shown (neglecting foreground subtraction; 4 MHz band, 100 hrs)

� Also image individual (but large) HII regions at z~6.5

� Instrument emphasizes:� Survey speed� Data quality� Calibration

� Simulated data shown (neglecting foreground subtraction; 4 MHz band, 100 hrs)

� Also image individual (but large) HII regions at z~6.5

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ConclusionsConclusions

� Reionization is complex and inhomogeneous� All current constraints are difficult to interpret!

� Topology carries enormous amount of information about source/IGM interactions

� Observational probes are on their way� Careful interpretation of QSO/GRB spectra (SDSS,

Swift: soon!)� Lyα galaxies (soon?)� Secondary CMB anisotropies (~3 years)� 21 cm emission (~3 years)

� Reionization is complex and inhomogeneous� All current constraints are difficult to interpret!

� Topology carries enormous amount of information about source/IGM interactions

� Observational probes are on their way� Careful interpretation of QSO/GRB spectra (SDSS,

Swift: soon!)� Lyα galaxies (soon?)� Secondary CMB anisotropies (~3 years)� 21 cm emission (~3 years)

the topology of reionization

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