Cosmic reionization and the history of the neutral intergalactic medium
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Cosmic reionization and the history of the neutral intergalactic medium MAGPOP Summer School, Kloster Seeon Chris Carilli, NRAO, August 10, 2007. Introduction: What is Cosmic Reionization? Current constraints on the IGM neutral fraction with cosmic epoch

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Cosmic reionization and the history of the neutral intergalactic medium

Cosmic reionization and the history of the neutral intergalactic medium

MAGPOP Summer School, Kloster Seeon

Chris Carilli, NRAO, August 10, 2007

  • Introduction: What is Cosmic Reionization?

  • Current constraints on the IGM neutral fraction with cosmic epoch

  • Neutral Intergalactic Medium (IGM) – HI 21cm signals

  • Low frequency telescopes and observational challenges


Cosmic reionization and the history of the neutral intergalactic medium

  • References

  • Reionization and HI 21cm studies of the neutral IGM

  • “Observational constraints on cosmic reionization,” Fan, Carilli, Keating 2006, ARAA, 44, 415

  • “Cosmology at low frequencies: the 21cm transition and the high redshift universe,” Furlanetto, Oh, Briggs 2006, Phys. Rep., 433, 181

  • Early structure formation and first light

  • “The first sources of light and the reionization of the universe,” Barkana & Loeb 2002, Phys.Rep., 349, 125

  • “The reionization of the universe by the first stars and quasars,” Loeb & Barkana 2002, ARAA, 39, 19

  • “Observations of the high redshift universe,” Ellis 2007, Saas-Fe advanced course 36


Cosmic reionization and the history of the neutral intergalactic medium

History of Baryons in the Universe

Ionized

Neutral

Reionized


Cosmic reionization and the history of the neutral intergalactic medium

Chris Carilli (NRAO)

Berlin June 29, 2005

WMAP – structure from the big bang


Cosmic reionization and the history of the neutral intergalactic medium

Hubble Space Telescope Realm of the Galaxies


Cosmic reionization and the history of the neutral intergalactic medium

Dark Ages

Epoch of Reionization

Twilight Zone

  • Last phase of cosmic evolution to be tested

  • Bench-mark in cosmic

    structure formation

    indicating the first

    luminous structures


Cosmic reionization and the history of the neutral intergalactic medium

Dark Ages

Epoch of Reionization

Twilight Zone

  • Epoch?

  • Process?

  • Sources?


Cosmic reionization and the history of the neutral intergalactic medium

Reionization: the movie

Gnedin 03

8Mpc comoving


Cosmic reionization and the history of the neutral intergalactic medium

Constraint I: Gunn-Peterson Effect

z

Barkana and Loeb 2001


Cosmic reionization and the history of the neutral intergalactic medium

Gunn-Peterson Effect toward z~6 SDSS QSOs

Fan et al 2006


Cosmic reionization and the history of the neutral intergalactic medium

Gunn-Peterson limits to f(HI)

GP = 2.6e4 f(HI) (1+z)^3/2

End of reionization?

f(HI) <1e-4 at z= 5.7

f(HI) >1e-3 at z= 6.3

  •  to f(HI) conversion requires ‘clumping factor’

  •  >>1 for f(HI)>0.001 => low f() diagnostic

  • GP => Reionization occurs in ‘twilight zone’, opaque for obs <0.9 m


Cosmic reionization and the history of the neutral intergalactic medium

Contraint II: The CMB

Temperature fluctuations due to density inhomogeneities at the surface of last scattering (z ~ 1000)

Sound horizon at recombination ~ 1deg

Angular power spectrum ~ variance on given angular scale ~ square of visibility function

Sachs-Wolfe


Cosmic reionization and the history of the neutral intergalactic medium

Reionization and the CMB

No reionization

Reionization

  • Thomson scatting during reionization (z~10)

  • Acoustics peaks are ‘fuzzed-out’ during reionization.

  • Problem: degenerate with intrinsic amplitude of the anisotropies.


Cosmic reionization and the history of the neutral intergalactic medium

CMB large scale polarization -- Thomson scattering during reionization

Page + 06; Spergel 06

  • Scattering CMB local quadrapole => polarized

  • Large scale: horizon scale at reionization ~ 10’s deg

  • Signal is weak:

  • TE = 10% TT (few uK)

  • EE = 1% TT

  • EE (l ~ 5)~ 0.3+/- 0.1 uK

TT

TE

EE

e ~ l / mfp ~ l nee(1+z)^2 = 0.09+/-0.03


Cosmic reionization and the history of the neutral intergalactic medium

Constraint II: CMB large scale polarization -- Thomson scattering during reionization

  • Rules-out high ionization fraction at z> 15

  • Allows for finite (~0.2) ionization to high z

  • Most action occurs at z ~ 8 to 14, with f(HI) < 0.5

TT

TE

EE

Page + 06; Spergel 06


Cosmic reionization and the history of the neutral intergalactic medium

Combined CMB + GP constraints on reionization

  • e = integral measure to recombination=> allows many IGM histories

  • Still a 3 result (now in EE vs. TE before)


Cosmic reionization and the history of the neutral intergalactic medium

Pushing into reionization: QSO 1148+52 at z=6.4

  • tuniv = 0.87Gyr

  • Lbol = 1e14 Lo

  • Black hole: ~3 x 109 Mo (Willot etal.)

  • Gunn Peterson trough (Fan etal.)


Cosmic reionization and the history of the neutral intergalactic medium

1148+52 z=6.42: Gas detection

46.6149 GHz

CO 3-2

Off channels

Rms=60uJy

VLA

IRAM

  • M(H2) ~ 2e10 Mo

  • zhost = 6.419 +/- 0.001

    (note: zly = 6.37 +/- 0.04)

VLA


Cosmic reionization and the history of the neutral intergalactic medium

Constrain III: Cosmic Stromgren Sphere

  • Accurate zhost from CO: z=6.419+/0.001

  • Proximity effect: photons leaking from 6.32<z<6.419

White et al. 2003

z=6.32

  • ‘time bounded’ Stromgren sphere: R = 4.7 Mpc

  • tqso = 1e5 R^3 f(HI)~ 1e7yrs or

  • f(HI) ~ 1 (tqso/1e7 yr)


Cosmic reionization and the history of the neutral intergalactic medium

Loeb & Rybicki 2000


Cosmic reionization and the history of the neutral intergalactic medium

CSS: Constraints on neutral fraction at z~6

  • Nine z~6 QSOs with CO or MgII redshifts:<R> = 4.4 Mpc (Wyithe et al. 05; Fan et al. 06; Kurk et al. 07)

  • GP => f(HI) > 0.001

  • If f(HI) ~ 0.001, then <tqso> ~ 1e4 yrs – implausibly short given QSO fiducial lifetimes (~1e7 years)?

  • Probability arguments + size evolution suggest: f(HI) > 0.05

Wyithe et al. 2005

Fan et al 2005

P(>xHI)

90% probability

x(HI) > curve

=tqso/4e7 yrs


Cosmic reionization and the history of the neutral intergalactic medium

  • Difficulties for Cosmic Stromgren Spheres

  • (Lidz + 07, Maselli + 07)

  • Requires sensitive spectra in difficult near-IR band

  • Sensitive to R: f(HI)  R^-3

  • Clumpy IGM => ragged edges

  • Pre-QSO reionization due to star forming galaxies, early AGN activity


Cosmic reionization and the history of the neutral intergalactic medium

OI

  • Not ‘event’ but complex process, large variance: zreion ~ 14 to 6

  • Good evidence for qualitative change in nature of IGM at z~6

ESO


Cosmic reionization and the history of the neutral intergalactic medium

3, integral measure?

Geometry, pre-reionization?

Local ionization?

OI

Abundance?

Saturates, HI distribution function, pre-ionization?

Local ioniz.?

  • Current probes are all fundamentally limited in diagnostic power

  • Need more direct probe of process of reionization = HI 21cm line

ESO


Cosmic reionization and the history of the neutral intergalactic medium

Low frequency radio astronomy: Most direct probe of the neutral IGM during, and prior to, cosmic reionization, using the redshifted HI 21cm line: z>6 => 100 – 200 MHz

Square Kilometer Array


Cosmic reionization and the history of the neutral intergalactic medium

HI mass limits => large scale structure

Reionization

1e13 Mo

1e9 Mo


Cosmic reionization and the history of the neutral intergalactic medium

HI 21cm radiative transfer: large scale structure of the IGM

LSS: Neutral fraction / Cosmic density / Temperature: Spin, CMB


Cosmic reionization and the history of the neutral intergalactic medium

Dark Ages HI 21cm signal

  • z > 200: T = TK = Ts due to collisions + Thomson scattering => No signal

  • z ~ 30 to 200: TK decouples from T, but collisions keep Ts ~ TK => absorption signal

  • z ~ 20 to 30: Density drops  Ts~ T => No signal

    Barkana & Loeb: “Richest of all cosmological data sets”

  • Three dimensional in linear regime

  • Probe to k ~ 10^3 /Mpc vs. CMB limit set by photon diffusion ~ 0.2/Mpc

  • Alcock-Pascinsky effect

  • Kaiser effect + peculiar velocites

T = 2.73(1+z)

TK = 0.026(1+z)^2

Furlanetto et al. 2006


Cosmic reionization and the history of the neutral intergalactic medium

TK

T

Enlightenment and Cosmic Reionization-- first luminous sources

  • z ~ 15 to 20: TScouples to TK via Lya scattering, but TK < T => absorption

  • z ~ 6 to 15: IGM is heated (Xrays, Lya, shocks), partially ionized => emission

  • z < 6: IGM is fully ionized


Cosmic reionization and the history of the neutral intergalactic medium

Signal I: Global (‘all sky’) reionization signature

Signal ~ 20mK < 1e-4 sky

Feedback in Galaxy formation

No Feedback

Possible higher z absorption signal via Lya coupling of Ts -- TK due to first luminous objects

Furlanetto, Oh, Briggs 06


Cosmic reionization and the history of the neutral intergalactic medium

Signal II: HI 21cm Tomography of IGM Zaldarriaga + 2003

z=12

9

7.6

  • TB(2’) = 10’s mK

  • SKA rms(100hr) = 4mK

  • LOFAR rms (1000hr) = 80mK


Cosmic reionization and the history of the neutral intergalactic medium

Signal III: 3D Power spectrum analysis

only

LOFAR

 + f(HI)

SKA

McQuinn + 06


Cosmic reionization and the history of the neutral intergalactic medium

Signal IV: Cosmic Web after reionization

Ly alpha forest at z=3.6 ( < 10)

Womble 96

  • N(HI) = 1e13 – 1e15 cm^-2, f(HI/HII) = 1e-5 -- 1e-6 => before reionization N(HI) =1e18 – 1e21 cm^-2

  • Lya ~ 1e7 21cm => neutral IGM opaque to Lya, but translucent to 21cm


Cosmic reionization and the history of the neutral intergalactic medium

Signal IV: Cosmic web before reionization: HI 21Forest

19mJy

z=12

z=8

130MHz

159MHz

  • radio G-P (=1%)

  • 21 Forest (10%)

  • mini-halos (10%)

  • primordial disks (100%)

  • Perhaps easiest to detect (use long baselines)

  • ONLY way to study small scale structure during reionization


Cosmic reionization and the history of the neutral intergalactic medium

Radio sources beyond the EOR

sifting problem (1/1400 per 20 sq.deg.)

1.4e5 at z > 6

S120 > 6mJy

2240 at z > 6


Cosmic reionization and the history of the neutral intergalactic medium

Signal V: Cosmic Stromgren spheres around z > 6 QSOs

  • LOFAR ‘observation’:

  • 20xf(HI)mK, 15’,1000km/s

  • => 0.5 x f(HI) mJy

  • Pathfinders: Set first hard limits on f(HI) at end of cosmic reionization

  • Easily rule-out cold IGM (T_s < T_cmb): signal = 360 mK

5Mpc

0.5 mJy

Wyithe et al. 2006


Cosmic reionization and the history of the neutral intergalactic medium

Signal VI: Dark Ages: Baryon Oscillations

Very low frequency (<75MHz) = Long Wavelength Array

  • Very difficult to detect

  • Signal: 10 arcmin, 10mk => S30MHz = 0.02 mJy

  • SKA sens in 1000hrs:

  • = 20000K at 50MHz =>

  • rms = 0.2 mJy

  • Need > 10 SKAs

  • Need DNR > 1e6

z=50

z=150

Barkana & Loeb 2005


Cosmic reionization and the history of the neutral intergalactic medium

Challenge I: Low frequency foreground – hot, confused sky

Eberg 408 MHz Image (Haslam + 1982)

  • Coldest regions: T ~ 100 (/200 MHz)^-2.6 K

  • 90% = Galactic foreground

  • 10% = Egal. radio sources ~ 1 source/deg^2 with S140 > 1 Jy


Cosmic reionization and the history of the neutral intergalactic medium

  • Solution: spectral decomposition (eg. Morales, Gnedin…)

  • Foreground = non-thermal = featureless over ~ 100’s MHz

  • Signal = fine scale structure on scales ~ few MHz

Signal/Sky ~ 2e-5

10’ FoV; SKA 1000hrs

Cygnus A

500MHz

5000MHz

Simply remove low order polynomial or other smooth function?


Cosmic reionization and the history of the neutral intergalactic medium

Crosscorrelation in frequency, or 3D power spectral analysis: different symmetries in frequency space for signal and foregrounds.

Freq

Foreground

Signal

Morales 2003


Cosmic reionization and the history of the neutral intergalactic medium

Cygnus A at WSRT 141 MHz 12deg field(de Bruyn)

Frequency differencing  ‘errors’ are ‘well-behaved’

‘CONTINUUM’ (B=0.5 MHz) ‘LINE’ CHANNEL (10 kHz) - CONT

(Original) peak: 11000 Jy noise 70 mJy

dynamic range ~ 150,000 : 1


Cosmic reionization and the history of the neutral intergalactic medium

30o x 30o

Galactic foreground polarization‘interaction’ with polarized beams frequency dependent residuals! Solution: good calibration of polarization response

NGP 350 MHz 6ox6o ~ 5 K pol

IF Faraday-thin  40 K at 150 MHz

WENSS: Schnitzeler et al A&A Jan07


Cosmic reionization and the history of the neutral intergalactic medium

Challenge II: Ionospheric phase errors – varying e- content

TID

74MHz Lane 03

  • ‘Isoplanatic patch’ = few deg = few km

  • Phase variation proportional to wavelength^2


Cosmic reionization and the history of the neutral intergalactic medium

Ionospheric phase errors: The Movie

  • Solution:

  • Wide field ‘rubber screen’ phase self-calibration = ‘peeling’

  • Requires build-up of accurate sky source model

15’

Virgo A 6 hrs VLA 74 MHz Lane + 02


Cosmic reionization and the history of the neutral intergalactic medium

Challenge III: Interference

100 MHz z=13

200 MHz z=6

  • Solutions -- RFI Mitigation (Ellingson06)

  • Digital filtering: multi-bit sampling for high dynamic range (>50dB)

  • Beam nulling/Real-time ‘reference beam’

  • LOCATION!


Cosmic reionization and the history of the neutral intergalactic medium

Beam nulling -- ASTRON/Dwingeloo (van Ardenne)

Factor 300 reduction in power


Cosmic reionization and the history of the neutral intergalactic medium

VLA-VHF: 180 – 200 MHz Prime focus CSS search Greenhill, Blundell (SAO); Carilli, Perley (NRAO)

Leverage: existing telescopes, IF, correlator, operations

  • $110K D+D/construction (CfA)

  • First light: Feb 16, 05

  • Four element interferometry: May 05

  • First limits: Winter 06/07


Cosmic reionization and the history of the neutral intergalactic medium

Project abandoned: Digital TV

KNMD Ch 9

150W at 100km


Cosmic reionization and the history of the neutral intergalactic medium

RFI mitigation: location, location location…

100 people km^-2

1 km^-2

0.01 km^-2

(Briggs 2005)


Cosmic reionization and the history of the neutral intergalactic medium

Multiple experiments under-way: ‘pathfinders’

LOFAR (NL)

MWA (MIT/CfA/ANU)

SKA

21CMA (China)


Cosmic reionization and the history of the neutral intergalactic medium

EDGES (Bowman & Rogers MIT)

All sky reionization HI experiment. Single broadband dipole experiment with (very) carefully controlled systematics + polynomial baseline subtraction (7th order)

VaTech Dipole Ellingson

rms = 75 mK

Sky > 150 K

Treion < 450mK at z = 6.5 to 10 (DNR ~ 2700)

(expect ~ 20mK)


Cosmic reionization and the history of the neutral intergalactic medium

GMRT 230 MHz – HI 21cm abs toward highest z (~5.2) radio AGN

0924-220 z=5.2

S230MHz = 0.5 Jy

GMRT at 230 MHz = z21cm

RFI = 20 kiloJy !

1”

8GHz Van Breugel et al.

CO Klamer +

M(H2) ~ 3e10 Mo


Cosmic reionization and the history of the neutral intergalactic medium

GMRT 230 MHz – HI 21cm abs toward highest z radio AGN (z~5.2)

  • Limits:

  • Few mJy/channel

  • Few percent in optical depth

232MHz 30mJy

229Mhz0.5 Jy

rms(40km/s) = 3mJy

rms(20km/s) = 5 mJy

N(HI) ~ 2e20TS cm^-2 ?


Cosmic reionization and the history of the neutral intergalactic medium

Focus: Reionization (power spec,CSS,abs)


Cosmic reionization and the history of the neutral intergalactic medium

PAPER: Staged Engineering Approach

  • Broad band sleeve dipole => 2x2 tile

  • 8 dipole test array in GB (06/07) => 32 station array in WA (12/07)

  • FPGA-based ‘pocket correlator’ from Berkeley wireless lab => custom design.

    BEE2: 5 FPGAs, 500 Gops/s

  • S/W Imaging, calibration, PS analysis: Miriad/AIPS => Python + CASA, including ionospheric ‘peeling’ calibration + MFS

  • ‘Peel the problem onion’

100MHz

200MHz


Cosmic reionization and the history of the neutral intergalactic medium

PAPERGB -- 8 Ant, 1hr, 12/06

RMS ~ 15Jy; DNR ~ 1e3

Cas A 1e3Jy

CygA 1e4Jy

5deg

W44 1e2Jy

HercA 1e2Jy


Cosmic reionization and the history of the neutral intergalactic medium

Destination: Moon!

  • No interference (ITU protected zone)

  • No ionosphere (?)

  • Easy to deploy and maintain (high tolerance electronics + no moving parts)

10MHz

Needed for probing ‘Dark ages’:

z>30 => freq < 50 MHz

RAE2 1973


Cosmic reionization and the history of the neutral intergalactic medium

Radio astronomy – Probing Cosmic Reionization

  • ‘Twilight zone’: study of first light limited to near-IR to radio

  • First constraints: GP, CMBpol => reionization is complex and extended:

    z_reion = 6 to 11

  • HI 21cm: most direct probe of reionization

  • Low freq pathfinders:

    All-sky, PS, CSS

  • SKA: imaging of IGM


Cosmic reionization and the history of the neutral intergalactic medium

END


Cosmic reionization and the history of the neutral intergalactic medium

Relative evolution of Ly-break and Ly galaxy populations: Obscuration by the neutral IGM (Ota + 2007)

LAE observed z=5.7

LAE predicted z=7 based on UV continuum

At z=7 => f(HI)=0.48+/-0.16

LAE obs z=7

  • Local ionization (CSS)?

  • Low S/N


Cosmic reionization and the history of the neutral intergalactic medium

Early structure formation: rules-of-thumb (Barkana & Loeb 2002)

Baryons: astrophysics

Dark Matter

Press-Schechter Formalism

  • M’Jeans’ = 1e4 Msun (z=20)

  • Minihalos: H2 cooling: Tvir = 300 to 1e4 K => M = 1e5 to 1e8 Msun issues:

    primordial H_2 formation?

    Near UV dissociates H_2?

    Soft Xray catalyzes H_2 formation?

    Preferentially form 100 M_sun stars (popIII)?

  • Protogalaxies: H line cooling => T_vir > 1e4 K

z M2 Tvir

Msun K

0 1e14 3e7

5 3e10 3e5

  • 6e7 8e3


Cosmic reionization and the history of the neutral intergalactic medium

Some basics

Structure formation: the Dark Matter perspective = Press-Schechter Formalism

z M_2s T_vir

M_sun K

0 1e14 3e7

5 3e10 3e5

10 6e7 8e3


Cosmic reionization and the history of the neutral intergalactic medium

Some basics

Structure formation: the Baryons

  • Minihalos z>15: M=1e5 to 1e8Mo => Tvir = 300 to 1e4 K => H2 cooling

    Primordial H2 formation?

    Near UV dissociates H2?

    Soft Xray catalyzes H2 formation?

    Preferentially form 100 Mo stars?

  • Protogalaxies z<15: 1e8Mo => Tvir > 1e4 K => HI line cooling

    [Cosmological Jeans mass < 1e4 Mo at z>20]


Cosmic reionization and the history of the neutral intergalactic medium

Cosmic Stromgren Surfaces (Hui & Haiman)

zhost

  • Larger CSS in Ly vs. Ly = Damping wing of Ly?

  • Large N(HI) (> 1e20cm^-2) => f(HI) > 0.1


Cosmic reionization and the history of the neutral intergalactic medium

GMRT Digital Filter in Lag-space (Pen et al. 2007)

150 MHz


Cosmic reionization and the history of the neutral intergalactic medium

Some basics: What’s time…?

At z > 8 trecombination < tuniv

At z>6

tuniv < 1 Gyr

Cen 2002

  • Stellar fusion produces 7e6eV/H atom.

  • Reionization requires 13.6eV/H atom

    =>Need to process only 1e-5 of baryons through stars to reionize the universe


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