Recent Results on Reionization
Chris Carilli (NRAO)
Dakota/Berkeley,August 2011
• CO intensity mapping during reionization: signal in 3 easy
steps
• Recent results on f(HI) at z > 6
 Gunn-Peterson overview
 Quasar near zones: a new tool
 J1120+0641 quasar at z=7.1: the Game Changer
 [Lya emission from z=7 LBGs: also in the Game]
ESO
Predicted mean CO brightness temperature in 3 simple steps
1.Cosmic star formation rate density required to reionize the IGM
using mean baryon density (Haardt & Madau, Bunker et al.)
 fescuv = ionizing photon escape fraction ~ 0.06 (MW), up to 0.2
for z~3 LBGs
 C = IGM clumping factor (recombinations) = 5 to 30
(simulations)
 Strong increase with z due to increase in mean cosmic baryon
density
2. Conversion of star formation rate to IR luminosity based on known
properties of galaxies (eg. Kennicutt 1998 and many others)
3. Conversion of IR luminosity to CO luminosity based on known
properties of galaxies (‘K-S law’; Daddi et al. 2010)
 Roughly linear relationship
between L’CO and LFIR for disk
galaxies at low and high z
 Similar slope for merger
driven starbursts, with different
normalization
 Disks likely dominate cosmic
star formation rate density
Doing some cosmic
algebra => mean
brightness temperature of
CO emission from the
galaxies that reionize the
neutral IGM at a given
redshift
[Not what we expect to
see at all redshifts, but
what is required to have
reionization occur at that
redshift.]
<TBsky>z=8 = 1.1 (0.1/fesc)-1 (C/5) uK
(1+z)3
Major uncertainties
• fesc – calibrated with JWST observations of 1st galaxies
• C – get handle via HI 21m observations (21cm forest
absorption?)
• Line confusion (30GHz = CO 2-1 z=6.7 or 1-0 at z=2.8):
requires dual frequency, cross correlation experiment (eg.
15 and 30GHz). Cross correlation with 21cm will also help
(Gong, Visbal)
• Early production of CO and dust (SFR – FIR – L’CO
relationships)
Early production of dust + CO: detections of
12 quasar host galaxies at z~6
M(dust) ~ 108Mo, M(H2) ~ 1010 Mo
z=6.42
0.15” TB ~ 25K
CO3-2 VLA
PdBI
-150 km/s
1” ~ 5.5kpc
7kpc
+
+150 km/s
SFR – FIR – L’CO relationships can be calibrated with
ALMA/EVLA/JWST observations of representative z>6 galaxy
samples.
6.4
Gunn-Peterson effect
SDSS z~6 quasars
• Increase of τGP with z
• Opaque at z>6
z=6.4
5.7
Gunn-Peterson opacity => f(HI)
• GP
f(HI) (1+z)3/2
• GP > 5 at z>6 => f(HI) >
few x 10-3
• Note: saturates at low
neutral fraction
• τ depends on clumping
factor and resolution
Fan, Carilli, Keating
Local
ionization?
• GP => likely substantial increase in f(HI) at z~6
• CMBpol => substantial ionization fraction persisting to z~11
Quasar Near Zones: J1148+5251
• Accurate host galaxy
redshift from CO: z=6.419
• Quasar spectrum =>
photons leaking down to
z=6.32
• ‘time bounded’ Stromgren
sphere ionized by quasar
White et al. 2003
Difference in zhost and zGP => RNZ = 4.7Mpc
6.32
[fHI Lγ tQ]1/3 (1+z)-1
HI
HII
Loeb & Barkana
Quasar Near-Zones: sample of 28 quasars at z=5.7 to 6.5
• Need: zhost and zGP
• GP on-set redshift: empirical approach
 Adopt fixed resolution of 20A
 Find 1st point when transmission drops below 10% (of
extrapolated) = well above typical GP level.
 => Relative, not absolute measurement
z = 6.1
Wyithe et al. 2010
Host galaxy redshifts: CO (12), [CII] (3), MgII (14), UV (8)
dz = 0.05 for UV lines
dz = 0.01 for MgII
dz = 0.003 for CO, [CII]
Quasar Near-Zones: 28 GP quasars at z=5.7 to 6.5
LUV
R
Lγ1/3
LUV
• No correlation of UV luminosity with redshift
• Correlation of RNZ with UV luminosity
Quasar Near-Zones: RNZ vs redshift
[normalized to M1450 = -27]
RNZ = 7.3 – 6.5(z-6)
z>6.15
<RNZ> decreases by factor 2.3 from z=5.7 to 6.5
If CSS => fHI increases by factor ~ 10 (eg. 10-4 to 10-3)
Alternative hypothesis to Stromgren sphere: Quasar
Proximity Zones (Bolton & Wyithe)
• RNZ measures where density of ionizing photon from quasar >
background photons (IGRF) =>
RNZ
[Lγ]1/2 (1+z)-9/4
• Increase in RNZ from z=6.5 to 5.7 is then
due to rapid increase in mfp during overlap/
‘percolation’ stage of reionization
• Either case (CSS or PZ) => rapid
evolution of IGM from z ~ 5.7 to 6.5
Local
ionization?
QNZ
Q-NZ: support substantial increase in f(HI) at z ~ 6 to 7
ESO
Breaking news: highest redshift quasar, z=7.1
• Clear GP absorption trough: τ > 5 => IGM opaque to Lya
•How to form 109 Mo black hole in 750Myr?
Mortlock ea.
z=6.2, 6.4
z=7.1 quasar near zone
• Small ~ 2Mpc
• Continues trend for decreasing NZ size
z=7.1 quasar: Damped Lya profile
• N(HI) > 1020.5 cm-2
• Substantially neutral
IGM: f(HI) > 0.1 at
2Mpc distance or
• Damped Lya galaxy
at 2Mpc (probability ~
5%) (Bolton ea.)
0.5
f(HI)=0.1
1.0
N(HI)=4e20 cm-2 at 2.6Mpc
6.4
Gunn-Peterson
effect
z=6.4
5.7
Q-DLA
Local
ionization?
QNZ
Q-DLA = Best evidence to date for very rapid rise in neutral
fraction from z=6 to 7, ie. ‘cosmic phase transition’
ESO
CMB large scale polarization
 Rules-out high ionization
fraction at z > 15
 Allows for small (≤ 0.2)
ionization to high z
 Most action occurs at z ~
7 to 15
 Challenge: systematics
extracting large scale signal
Dunkley et al. 2008
END
ESO
LBG galaxies at z=7: Lya spectroscopy
Observed increase in fraction of
Lya detections of LBG with z
LBG at z=7: fewer detected in
Lya than expected
• Expect 9, detect 3 (two
independent samples) =>
• Attenuation of Lya emission
by wings of DLA due to neutral
IGM or
• Change in galaxy properties
from z=6 to 7
• More interlopers than they
thought
Schenker ea
Pentericci ea
Pentericci ea: if drop-off in detections is due to DLA
of IGM, modeling => f(HI) > 0.4 at z=7
LBGDLA
QDLA
Local
ionization?
Q-NZ
Cosmic phase transition! Numerous lines of evidence support a
very rapid rise in neutral fraction at z ~ 6 to 7
END
ESO
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(or more), in all areas of (sub)mm
astronomy, including resolution,
sensitivity, and frequency coverage.
ALMA Control
Building
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ALMA+EVLA = Order magnitude
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What is the EVLA? similar
ten-fold improvement in
most areas of cm astronomy
•frequencies = 1 to 50 GHz
•8 GHz BW => 80x old
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ALMA Status
•Antennas, receivers, correlator in
production: best submm receivers and
antennas ever!
•Site construction well under way:
Observation Support Facility, Array
Operations Site, 5 Antenna
interferometry at high site!
• Early science call Q1 2011
5 antennas on high site
EVLA Status
•Antenna retrofits 70% complete
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•Early science in March 2010
using new correlator (2GHz)
•Full receiver complement
completed 2012 + 8GHz