1. SKA KSP: probing cosmic reionization and the first galaxies
Manchester, Oct 2007
Chris Carilli (NRAO)
Ionized
Neutral
Reionized

2. WMAP – structure from the big bang
Chris Carilli (NRAO)
Berlin June 29, 2005
WMAP – structure from the big bang

3. Realm of the Galaxies

4. Dark Ages Cosmic reionization
Last phase of cosmic evolution to be explored
Benchmark in cosmic structure formation indicating the formation of the first luminous objects.
HI 21cm line is most direct, incisive probe of structure formation during, and process of, reionization.
Radio(cm/mm) observations reveal the gas, dust, star formation, and AGN in the earliest galaxies
Dark Ages
Cosmic reionization

5. Constraint I: Gunn-Peterson Effect
End of reionization?
f(HI) > 1e-3 at z = 6.3
f(HI) < 1e-4 at z= 5.7
IGM opaque at obs < 1um
Fan et al 2006

6.  = 0.09+/-0.03 => zreion = 11+/-3
Constraint II: CMB large scale polarization: Thompson scattering during reionization
Scattered CMBquad. => polarized
Horizon scale ~ 10’s deg
EE ~ 1% TT
 = 0.09+/ => zreion = 11+/-3 TT TE EE
Fan et al 2003
Page + 06

7. Not ‘event’ but complex process, large variance: zreion ~ 14 to 6 OI
Fan, Carilli, Keating ARAA 2006
Not ‘event’ but complex process, large variance: zreion ~ 14 to 6
Good evidence for qualitative change in nature of IGM at z~6
ESO

8. Current probes are all fundamentally limited in diagnostic power OI
Saturates, HI distribution function, pre-ionization?
Abundance?
3, integral measure?
Local ionization?
Geometry, pre-reionization?
Local ioniz.?
Current probes are all fundamentally limited in diagnostic power
Need more direct probe of process of reionization = HI 21cm line
ESO

9. Large scale structure: cosmic density,  neutral fraction, f(HI)
KSP part I: Studying the pristine IGM into the EOR using redshifted HI 21cm observations (100 – 200 MHz)
Large scale structure:
cosmic density, 
neutral fraction, f(HI)
Temp: TK, TCMB, Tspin
Heating: Ly, Xrays, shocks
1e13
1e9

10. Signal I: Global (‘all sky’) reionization signature in low frequency HI spectra
IGM heating: Tspin=TK > TCMB
Lya coupling: Tspin=TK < TCMB
130MHz
190MHz
Gnedin & Shaver 03
21cm ‘deviations’ < 1e-4 wrt foreground

11. Signal II: HI 21cm Tomography of IGM Zaldarriaga + 20039
7.6
TB(2’) = 10’s mK
SKA rms(100hr) = 4mK
LOFAR rms (1000hr) = 80mK

12. Signal III: 3D Power spectrum analysis
only
LOFAR
 + f(HI)
SKA
McQuinn + 06

13. Cosmic Web after reionization
Ly alpha forest at z=3.6 ( < 10)
Womble 96
N(HI) = 1e13 – 1e15 cm^-2, f(HI/HII) = 1e e-6
=> Before reionization N(HI) =1e18 – 1e21 cm^-2

14. Signal IV: Cosmic web before reionization: HI 21Forest
19mJy
z=12
z=8
130MHz
radio G-P (=1%)
21 Forest (10%)
mini-halos (10%)
primordial disks (100%)
Only method to study small scale structure
expect 0.05 to 0.5 deg^-2 at z> 6 with S_151 > 6 mJy

15. ‘Pathfinders’: First light 2007/2008
MWA (MIT/ANU)
LOFAR (NL)
PAST (CMU/China)
PAPER Berk/NRAO

16. Challenge I: Low frequency foreground – hot, confused sky
Eberg 408 MHz Image (Haslam )
Coldest regions: T = 100 (/200 MHz)^-2.6 K
Highly ‘confused’: 1 source/deg^2 with S140 > 1 Jy

17. Solution: spectral decomposition (eg. Morales, Gnedin…)
Foreground = non-thermal = featureless over ~ 100’s MHz
Signal = fine scale structure on scales ~ few MHz
Cygnus A
10’ FoV; SKA 1000hrs
Signal/Sky ~ 2e-5
500MHz
5000MHz
Remove low order polynomial or other smooth function?
Cross correlation in channels, or 3D power spectrum

18. Challenge II Ionospheric phase errors: varying e- content
TID
100”
-100”
74MHz Lane 03
‘Isoplanatic patch’ = few deg = few km
Phase variation proportional to wavelength^2
Solution: Wide field ‘rubber screen’ phase self-calibration

19. Challenge III – RFI: location, location, location…
100 people km^-2
1 km^-2
0.01 km^-2

20. KSP part II -- first galaxies: CO redshift coverage
Epoch of Reionization:
First galaxies: standard molecular transitions redshift to cm regime
Total gas mass
Gas dynamics
Gas excitation
High density gas tracers

21. First galaxies -- Radio astronomy into cosmic reionization
z ~ 6 QSO host galaxies: molecular gas and dust
z=6.42
VLA
50K
PdBI
FWHM=350 km/s
Radio-FIR correlation
Mdust ~ 1e8 Mo
Dust heating: star formation or AGN?
Follows Radio-FIR correlation: SFR ~ 3000 Mo/yr
Giant reservoirs of molecular gas ~2e10 Mo = fuel for star formation.
Currently: 3 solid detections, 1 likely at z~6

22. VLA imaging of gas at subkpc resolution
J : VLA imaging of CO3-2
VLA imaging of gas at subkpc resolution
0.4”res
rms=50uJy at 47GHz
1” kpc
0.15” res
Not just circumnuclear disk.
Mdyn~ 4e10Mo ~ Mgas >> Mbulge ~1e12 Mo predicted by M-
Only probe of host galaxy
Separation = 0.3” = 1.7 kpc
TB = 20K => Typical of starburst nuclei

23. [CII] 158um ISM gas cooling line at z=6.4
30m 256GHz Maiolino etal
C+ = workhorse line for z>6 galaxies with ALMA
Structure identical to CO 3-2” (~ 5 kpc) => distributed gas heating = star formation?
SFR ~ 6.5e-6 L[CII] ~ 3000 Mo/yr
CII PdBI Walter et al.
CII + CO 3-2 1”

24. Higher Density (ncr>1e4 cm^-3) Tracers: HCN, CN, HCO+
Riechers
Linearly correlated with FIR => dense gas directly associated with star forming clouds
Lines 5-10x fainter than CO
ncr > 1e7cm^-3 for higher orders => higher order not (generally) excited?
Dense gas tracers: exclusive regime of cm telescopes
200uJy

25. Building a giant elliptical galaxy + SMBH at tuniv < 1Gyr10
10.5
Multi-scale simulation isolating most massive halo in 3 Gpc^3 (co-mov)
Stellar mass ~ 1e12 Mo forms in series (7) of major, gas rich mergers from z~14, with SFR ~ 1e3 - 1e4 Mo/yr
SMBH of ~ 2e9 Mo forms via Eddington-limited accretion + mergers
Evolves into giant elliptical galaxy in massive cluster (3e15 Mo) by z=0
8.1
Li, Hernquist, Roberston, Dave ..
6.5
Enrichment of heavy elements, dust starts early (z > 8): good news for radio astronomy
Extreme and rare objects: ~ 100 SDSS z~6 QSOs on entire sky
Integration times of hours to days to detect HyLIGRs

26. The need for collecting area: pushing to normal galaxies at high redshift -- spectral lines
cm telescopes: low order molecular transitions
(sub)mm: high order molecular lines + fine structure lines

27. (sub)mm Dust, molecular gas Near-IR: Stars, ionized gas, AGN
The need for collecting area: continuum
A Panchromatic view of galaxy formation
Arp 220 vs z
cm: Star formation, AGN
(sub)mm Dust, molecular gas
Near-IR: Stars, ionized gas, AGN

28. Radio astronomy – Reionization and 1st galaxies
‘Twilight zone’: study of first light limited to near-IR to radio wavelengths
First constraints: GP, CMBpol => reionization is complex and extended: zreion = 6 to 14
HI 21cm: most direct probe of reionization
- Low freq pathfinders: All-sky, PS, CSS, Abs
- SKA: imaging of IGM
First galaxies: cm/mm -- gas, dust, star formation, AGN

29. END

30. Signal VI: pre-reionization HI signal: ‘richest of all cosmological data sets’ eg. Baryon Oscillations (Barkana & Loeb)
Very difficult to detect !
z=50 => n = 30 MHz
Signal: 30 arcmin, 50 mk => S_30MHz = 0.1 mJy
SKA sens in 1000hrs:
T_fg = 20000K =>
rms = 0.2 mJy
z=50
z=150

31. 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