Cosmic reionization and the history of the neutral intergalactic medium LANL Chris Carilli May 23, 2007 Current constraints on the IGM neutral fraction with cosmic epoch (Fan, Carilli, Keating 2006 ARAA) Neutral Intergalactic Medium (IGM) – HI 21cm telescopes, signals, and challenges Objects within reionization – recent observations of molecular gas, dust, and star formation, in the host galaxies of the most distant QSOs, and more…
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Cosmic reionization and the history of the neutral intergalactic medium LANL
Cosmic reionization and the history of the neutral intergalactic medium LANL Chris Carilli May 23, 2007. Current constraints on the IGM neutral fraction with cosmic epoch (Fan, Carilli, Keating 2006 ARAA) Neutral Intergalactic Medium (IGM) – HI 21cm telescopes, signals, and challenges - PowerPoint PPT Presentation
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Cosmic reionization and the history of the neutral intergalactic medium
LANL
Chris Carilli May 23, 2007
Current constraints on the IGM neutral fraction with cosmic epoch (Fan, Carilli, Keating 2006 ARAA)
Neutral Intergalactic Medium (IGM) – HI 21cm telescopes, signals, and challenges
Objects within reionization – recent observations of molecular gas, dust, and star formation, in the host galaxies of the most distant QSOs, and more…
Ionized
Neutral
Reionized
Chris Carilli (NRAO)
Berlin June 29, 2005
WMAP – structure from the big bang
Hubble Space Telescope Realm of the Galaxies
Dark Ages
Twilight Zone
Epoch of Reionization
• Last phase of cosmic evolution to be tested • Bench-mark in cosmic structure formation indicating the first luminous structures
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
Gnedin 03
Reionization: the movie
8Mpc comoving
Barkana and Loeb 2001
Constraint I: Gunn-Peterson Effect
z
Gunn-Peterson Effect
Fan et al 2006
Gunn-Peterson limits to f(HI)
End of reionization?
f(HI) <1e-4 at z= 5.7
f(HI) >1e-3 at z= 6.3
Difficulties with GP
• 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
GP = 2.6e4 f(HI) (1+z)^3/2
Reionization and the CMB
Thomson scatting during reionization (z~10)
Acoustics peaks are ‘fuzzed-out’ during reionization.
Problem: degenerate with intrinsic amplitude of the anisotropies.
Surface of last-scattering z~1000
No reionization
Reionization
CMB angular power spectrum
TT
TE
EE
Constraint II: CMB large scale polarization -- Thomson scattering during reionization
Scattered CMB 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
Page + 06; Spergel 06
TT
TE
EE
Constraint II: CMB large scale polarization -- Thomson scattering during reionization
e = 0.09+/-0.03
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
Page + 06; Spergel 06
es with CMB polarization:
e = integral measure to recombination=> allows many IGM histories
• Still a 3 result (now in EE vs. TE before)
Combined CMB + GP constraints on reionization
• Highest redshift quasar known (tuniv = 0.87Gyr)• Lbol = 1e14 Lo
• Black hole: ~3 x 109 Mo (Willot etal.)• Gunn Peterson trough (Fan etal.)
Pushing into reionization: QSO 1148+52 at z=6.4
1148+52 z=6.42: Gas detection
Off channelsRms=60uJy
46.6149 GHzCO 3-2
• M(H2) ~ 2e10 Mo
• zhost = 6.419 +/- 0.001
(note: zly = 6.37 +/- 0.04)
VLA
IRAM
VLA
Constrain III: Cosmic Stromgren Sphere
• Accurate zhost from CO: z=6.419+/0.001
• Proximity effect: photons leaking from 6.32<z<6.419
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
=tqso/4e7 yrs
90% probability x(HI) > curve
P(>xHI)
Fan et al 2005
Cosmic Stromgren Surfaces (Hui & Haiman)
• Larger CSS in Ly vs. Ly = Damping wing of Ly?
• Large N(HI) => f(HI) > 0.1
zhost
Difficulties for Cosmic Stromgren Spheres and Surfaces
(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 ‘phase transition’?
Not ‘event’ but complex process, large variance time/space
Current observations suggest: zreion ~ 6 to 14
Good evidence for qualitative change in nature of IGM at z~6
Current probes are all fundamentally limited in diagnostic power
Studying the pristine neutral IGM using redshifted HI 21cm observations (100 – 200 MHz)
Large scale structure
cosmic density,
neutral fraction, f(HI)
Temp: TK, TCMB, Tspin
)1()10
1)((008.0 2/1 δ +
+= HI
S
CMB fz
TT
1e13 Mo
1e9 Mo
Multiple experiments under-way: ‘pathfinders’
MWA (MIT/CfA/ANU) LOFAR (NL)
21CMA (China) SKA
Signal I: Global (‘all sky’) reionization signature in low frequency HI spectra
Ly coupling: Tspin=TK < TCMB
IGM heating: Tspin= TK > TCMB
Gnedin & Shaver 03
140MHz
Signal ~ 20mK < 1e-4 sky
EDGES (Bowman & Rogers MIT)
All sky reionization HI experiment. Single broadband dipole experiment with (very) carefully controlled systematics + polynomial baseline subtraction (7th order)
Treion < 450mK at z = 6.5 to 10
Sky > 150 K rms = 75 mK
VaTech Dipole Ellingson
Signal II: HI 21cm Tomography of IGM Zaldarriaga + 2003
•Low power super computing: LOFAR/Blue Gene = 0.15MW
•Lunar ionosphere: p = 0.2 to 1MHz (LUNA19,20 1970’s)?
•Diffraction limits: how sharp is knife’s edge?
Very low frequencies (<10MHz): Lunar challenges
ARTICLE 22(ITU Radio Regulations)
Space servicesSection V – Radio astronomy in the shielded zone of the Moon
22.22 § 8 1) In the shielded zone of the Moon31 emissions causing harmful inter ference to radio astronomy observations32 and to other users of passive services shall be prohibited in the entire frequency spectrum except in the following bands:
22.23 a) the frequency bands allocated to the space research service using active sensors;
22.24 b) the frequency bands allocated to the space operation service, the Earth exploration-satellite service using active sensors, and the radiolocation service using stations on spaceborne platforms, which are required for the support of space research, as well as for radiocommunications and space research transmissions within the lunar shielded zone.
22.25 2) In frequency bands in which emissions are not prohibited by Nos. 22.22 to 22.24, radio astronomy observations and passive space research in the shielded zone of the Moon may be protected from harmful interference by agreement between administrations concerned.
22.22.1 The shielded zone of the Moon comprises the area of the Moon’s surface and an adjacent volume of space which are shielded from emissions originating within a distance of 100 000 km from the centre of the Earth.
32 22.22.2 The level of harmful interference is determined by agreement between the administrations concerned, with the guidance of the relevant ITU-R Recommendations.
Good “news” …The Moon is radio protected!
• The back side of the moon is declared as a radio protected site within the ITU Radio Regulations
– The IT Radio Regulations are an international treaty within the UN.
– Details are specified in a published ITU Recommendation (this is a non-mandatory recommendation, but is typically adhered to).
Radio astronomy on the moon has been a long-standing goal, protected by international treaties!
Steps need to be taken to protect the pristine and clean nature of the moon.
Lunar communication on the far side needs to be radio quiet.