Radio astronomical probes of Cosmic Reionization
and the 1st luminous objects
Chris Carilli April 3, 2007 MIT

Brief introduction to cosmic reionization

Objects within reionization – recent observations of molecular
gas, dust, and star formation, in the host galaxies of the most
distant QSOs, and more…

Neutral Intergalactic Medium (IGM) – HI 21cm telescopes,
signals, and challenges
USA – Carilli, Wang, Fan, Strauss, Gnedin
Euro – Walter, Bertoldi, Cox, Menten, Omont
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
Constraint I:
Gunn-Peterson
Effect
End of reionization?
f(HI) <1e-4 at z= 5.7
f(HI) >1e-3 at z= 6.3
Constraint II: CMB large scale polarization -- Thompson
scattering during reionization
Page + 06; Spergel 06
TT
 Scattered CMB quad.
=> polarized
 Horizon scale => 10’s
deg
 e = 0.09+/-0.03
zreion= 11+/3
TE
EE
Fan, Carilli,
Keating
ARAA 06
QuickTime™ and a
YUV420 codec decompressor
are needed to see this picture.
8Mpc
Gnedin03
 Current observations => zreion = 6 to 11 (+/-3)
 Not ‘event’ but complex process, large variance time/space
(eg. Shull & Venkatesan 2006)
Limitations of measurements
CMB polarization
e = integral measure through universe
=> allows many
reionization scenarios
• Still a 3 result (now in EE vs. TE before)
Gunn-Peterson effect
• Lya to f(HI) conversion requires ‘clumping factor’ (cf. Becker
etal 06)
• Lya >>1 for f(HI)>0.001 => low f() diagnostic
GP => Reionization occurs in ‘twilight zone’, opaque for
obs <0.9 m
Radio observations of z ~ 6 QSO host galaxies
 IRAM 30m + MAMBO: sub-mJy sens
at 250 GHz + wide fields  dust
 IRAM PdBI: sub-mJy sens at 90 and
230 GHz +arcsec resol. mol. Gas, C+
 VLA: uJy sens at 1.4 GHz  star
formation
 VLA: < 0.1 mJy sens at 20-50 GHz +
0.2” resol.  mol. gas (low order)
Magic of (sub)mm: distance independent method of
studying objects in universe from z=0.8 to 10
L_FIR ~ 4e12 x S250(mJy) L_sun
SFR ~ 1e3 x S250 M_sun/yr
FIR = 1.6e12 L_sun
obs = 250 GHz
Why QSOs?
 Spectroscopic redshifts
 Extreme (massive) systems
MB < -26 =>
Lbol > 1e14 Lo
MBH > 1e9 Mo
 Rapidly increasing samples:
z>4: > 1000 known
z>5: 80
z>6: 15
Fan 05
QSO host galaxies –
MBH -- Mbulge relation
Magorrian, Tremaine, Gebhardt, Merritt…
 Most (all?) low z spheroidal galaxies have SMBH: MBH=0.002 Mbulge
‘Causal connection between SMBH and spheroidal galaxy formation’
 Luminous high z QSOs have massive host galaxies (1e12 Mo)
MAMBO surveys of z>2 QSOs
J1148+5251
1e13 Lo
2.4mJy
• 1/3 of luminous QSOs have S250 > 2 mJy, independent of redshift from
z=1.5 to 6.4
• LFIR =1e13 Lo = 0.1 x Lbol: Dust heating by starburst or AGN?
Pushing into reionization: QSO 1148+52 at z=6.4
• Highest redshift quasar known (tuniv = 0.87Gyr)
• Lbol = 1e14 Lo
• Black hole: ~3 x 109 Mo (Willot etal.)
• Gunn Peterson trough (Fan etal.)
1148+52 z=6.42:
Dust detection
MAMBO 250 GHz
3’
S250 = 5.0 +/- 0.6 mJy
LFIR = 1.2e13 Lo
Mdust =7e8 Mo
Dust formation?
• AGB Winds ≥ 1.4e9yr
• tuniv = 0.87e9yr
=> dust formation associated with high mass star formation: Silicate
gains (vs. eg. Graphite) formed in core collapse SNe (Maiolino 07)?
1148+52 z=6.42: Gas detection
VLA
46.6149 GHz
CO 3-2
IRAM
Off channels
Rms=60uJy
VLA
• FWHM = 305 km/s
• z = 6.419 +/- 0.001
• M(H2) ~ 2e10 Mo
• Mgas/Mdust ~ 30 (~ starburst galaxies)
• C, O production (~1e8 Mo) => Star
formation started early (z > 8)?
1148+52
CO Excitation
• Tk ~ 100K
• nH2 ~ 105 cm-3
=> Typical of starburst
galaxy nucleus
2
J1148+52: VLA imaging of CO3-2
0.4”res
rms=50uJy at 47GHz
1”
0.15” res
CO extended to NW by 1”
(=5.5 kpc) tidal(?) feature
 Separation = 0.3” = 1.7 kpc
 TB = 35K => Typical of
starburst nuclei
Merging galaxies?
Testing MBH - Mbulge relation at high z
CO FWHM + size =>
Mdyn~ 2e10/(sin)^2 Mo
Mgas~ 2e10 Mo
Mbulge ~1e12 Mo
(predicted)
1148+5251
1148+5251
Radio-IR
SED
TD = 50 K
Elvis
SED
Radio-FIR correlation
 FIR excess = 50K dust
 Radio-FIR SED follows star forming galaxy
 SFR ~ 3000 Mo/yr
[CII] 158um PDR cooling line detected at z=6.4
30m 256GHz
PdBI
Maiolino etal
0.3”
 L[CII] = 4x109 Lo
 Size ~ 0.5” (~ 2.5kpc)
 L[CII]/LFIR = 3x10-4 ~ ULIRG
 Enriched ISM on kpc scales
 SFR ~ 6.5e-6 L[CII] ~ 3000 Mo/yr
SDSS J0927+2001 z=5.8
 FIR-luminous QSO host + ‘submm galaxy’ companion
 separation = 87kpc
 Biased massive galaxy formation at early times?
SharkII CSO 850GHz rms= 6mJy
10”
Radio-FIR
correlation
LFIR ~ 1e13 Lo
SFR ~ 2500 Mo/yr
Chance projection < 1%
•FIR-luminous z~6 QSOs: SFR ~ few e3 Mo/yr => form
large spheroid in dynamical timescale ~ 1e8 yr
•Coeval formation of massive galaxy + SMBH within 1 Gyr
of big bang?
Z~6
Low z IR QSOs:
major mergers
AGN+starburst?
Low z Optical QSOs: earlytype hosts
Building a giant elliptical galaxy
+ SMBH by z=6.5
10.5
Li, Hernquist, Roberston..
 Multi-scale simulation isolating most
massive halo in 3 Gpc^3 (co-mov)
8.1
 Stellar mass ~ 1e12 Mo forms in
series (7) of major, gas rich mergers
from z~14, with SFR ~ 1e3 - 1e4 Mo/yr
6.5
 SMBH of ~ 2e9 Mo forms via
Eddington-limited accretion + mergers
 BH feedback regulates star formation
 ISM abundance quickly evolves to
solar
 Evolves into giant elliptical galaxy in
massive cluster (3e15 Mo) by z=0
Mstars=1e12Mo
MBH =
2e9Mo
The ALMA revolution -- observing normal galaxies into
cosmic reionization
Panchromatic
view of galaxy
formation:
ALMA reveals
the cool
universe: dust
and gas -- the
fundamental fuel
for star formation
LFIR = 1e11 Lo
cm: star formation,
AGN
(sub)mm dust,
molecular gas
Near-IR: stars,
ionized gas, AGN
Cosmic Stromgren Sphere
• Accurate redshift from CO: z=6.419+/0.001
Ly a, high ioniz Lines: inaccurate redshifts (z > 0.03)
• 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)
Loeb & Rybicki 2000
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 suggest: f(HI) > 0.1
P(>x_HI)
Wyithe et al. 2005
90% probability
x(HI) > curve
=tqso/4e7 yrs
Cosmic ‘phase
transition’?
 CSS => rapid rise in f(HI) around z ~ 6 to 7
 Many difficulties (Lidz + 07, Maselli + 07)
* f(HI)  R^-3
* pre-QSO reionization => clumpy IGM/ragged edges
Studying the pristine neutral IGM using redshifted HI 21cm
observations (100 – 200 MHz)
TCMB 1  z 1/ 2
  0.008(
)(
) f HI (1   )
TS
10
1e13 Mo
Large scale structure
 cosmic density, 
 neutral fraction, f(HI)
 Temp: TK, TCMB, Tspin
1e9 Mo
Multiple experiments under-way: ‘pathfinders’ ~1e4 m^2
MWA (MIT/CfA/ANU)
21CMA (China)
LOFAR (NL)
SKA 1e6 m^2
Signal I: Global (‘all sky’) reionization signature in low
frequency HI spectra
Gnedin & Shaver 03
140MHz
IGM heating: Tspin= TK > TCMB
Ly coupling: Tspin=TK < TCMB
All sky => Single dipole experiment
with (very) carefully controlled
systematics (signal <1e-4 sky), eg.
EDGES (Rogers & Bowman 07)
Signal II: HI 21cm Tomography of IGM
Zaldarriaga + 2003
z=12
9
TB(2’) = 10’s mK
SKA rms(100hr) = 4mK
LOFAR rms (1000hr) = 80mK
7.6
Signal III: 3D Power spectrum analysis
 only
LOFAR
 + f(HI)
SKA
McQuinn + 06
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
Signal IV: Cosmic web before reionization: HI 21Forest
19mJy
z=12
130MHz
• radio G-P (=1%)
• 21 Forest (10%)
• mini-halos (10%)
• primordial disks (100%)
z=8
159MHz
• Perhaps easiest to detect (use long
baselines)
• Requires radio sources: expect
0.05 to 0.5 deg^-2 at z> 6 with S151
> 6 mJy?
Signal V: Cosmic Stromgren spheres around z > 6 QSOs
 LOFAR ‘observation’:
20xf(HI)mK, 15’,1000km/s
5Mpc
=> 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
0.5 mJy
Wyithe et al. 2006
Challenge I: Low frequency foreground – hot, confused sky
Eberg 408 MHz Image (Haslam + 1982)
Coldest regions: T ~ 100 (/200Mz)^-2.6 K
Highly ‘confused’: 1 source/deg^2 with S140 > 1 Jy
Solution: spectral decomposition (eg. Morales, Gnedin…)
Foreground = power-law or gently curving over ~ 100 MHz
Signal = fine scale structure on scales ~ few MHz
Freq
Signal/Sky ~ 2e-5
Signal
10’ FoV; SKA 1000hrs
Foreground
Xcorrelation/Power spectral analysis in 3D – different
symmetries in freq space
Challenge II: Ionospheric phase errors – varying e- content
 TIDs – ‘fuzz-out’
sources
‘Isoplanatic patch’ =
few deg = few km
 Phase variation
proportional to ^2
QuickTime™ and a
Cinepak decompressor
are needed to see this picture.
Solution:
Wide field ‘rubber
screen’ phase selfcalibration
15’
Virgo A VLA 74 MHz Lane + 02
Challenge III: Interference
100 MHz
z=13
200 MHz
z=6
Solutions -- RFI Mitigation (Ellingson06)
 Digital filtering
 Beam nulling
 Real-time ‘reference beam’
 LOCATION!
VLA-VHF: 180 – 200 MHz Prime focus X-dipole
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
Project abandoned: Digital TV
KNMD Ch 9
150W at 100km
RFI mitigation: location, location location…
100 people km^-2
1 km^-2
0.01 km^-2
(Briggs 2005)
Destination: Moon!
 No interference
 No ionosphere (?)
RAE2 1973
GMRT 230 MHz – HI 21cm abs toward highest z radio galaxy and
QSO (z~5.2)
RFI = 20 kiloJy !
229Mhz 0.5 Jy
rms(20km/s) = 5 mJy
232MHz 30mJy
rms(40km/s) = 3mJy
N(HI) ~ 2e20TS cm^-2 ?
Radio astronomy probing cosmic reionization
•‘Twilight zone’: obs of 1st
luminous sources limited to near-IR
to radio wavelengths
• Currently -- pathological systems
(‘HLIRGs’): coeval formation
SMBH+giant ellipt. in spectacular
starburst at tuniv<1Gyr
•EVLA, ALMA 10-100x sensitivity
is critical to study normal galaxies
•Low freq pathfinders: HI 21cm
signatures of neutral IGM
•SKA: imaging of IGM
END
• Focus: Reionization (power spec,CSS,abs)
• Very wide field: 2x2 tile(?)
• Correlator: FPGA-based from Berkeley
wireless lab
• Staged engineering approach: GB05 8
stations  Boolardy07 16 stations
PAPER: First images/spectra
Cas A
1e4Jy
180MHz
140MHz
Cygnus A
CygA
1e4Jy 1e4Jy
3C348
400Jy
3C392
200Jy
ALMA first fringes (Emerson +)
ATF, Socorro NM
Saturn 90 GHz March 2, 2007
Using all ALMA electronics
ALMA Status
•Antennas, receivers, correlator all fully prototyped and evaluated: best mm receivers
and antennas ever!
•Site construction well under way: Observation Support Facility and Array
Operations Site
•North American ALMA Science Center (C’Ville): gearing up for science
commissioning and operations (successful international operations review Feb 2007)
•Timeline:
Q1 2007: First fringes at ATF (Socorro)
Q1 2009: Three antenna array at AOS
Q3 2010: Start early science (16 antennas)
Q4 2012: Full operations
Signal VI: pre-reionization HI signal
eg. Baryon Oscillations (Barkana & Loeb)
Very difficult to detect !
 z=50 =>  = 30 MHz
 Signal: 30 arcmin, 50 mk
=> S_30MHz = 0.1 mJy
 SKA sens in 1000hrs:
T_fg = 20000K =>
z=50
rms = 0.2 mJy
z=150
HCN emission: Dense gas directly associated with star formation
n(H2) > 1e5 cm^-3 (vs. CO: n(H2) > 1e3 cm^-3)
z>2
J1148+52
Solomon et al
z=2.58
70 uJy
index=1
Stratta, Maiolino et al. 2006:
extinction toward z=6.2 QSO and 6.3
GRB =>
Silicate + amorphous Carbon dust
grains (vs. eg. Graphite) formed in
core collapse SNe?
Sources responsible for reionization
 Luminous AGN: No
 Star forming galaxies: maybe -- dwarf
galaxies (Bowens05; Yan04)?
 mini-QSOs -- unlikely (soft Xray BG;
Dijkstra04)
 Decaying sterile neutrinos -- unlikely
(various BGs; Mapelli05)
 Pop III stars z>10? midIR BG
(Kashlinsky05), but trecomb < tuniv at z~10
GP => Reionization occurs in
‘twilight zone’, opaque for
obs <0.9 m
Needed
for
reion.
[CII] -- the good and the bad
 [CII]/FIR decreases
rapidly with LFIR (lower
heating efficiency due to
charged dust grains?) =>
luminous starbursts are still
difficult to detect in C+
 Normal star forming
galaxies (eg. LAEs) are not
much harder to detect!
J1148 z=6.4: gas, dust, star formation
• FIR excess ~ 1e13Lo, Md~7e8Mo
• Giant molecular gas cloud ~ 2e10Mo, size ~ 5.5kpc
• Star formation rate ~ 3000 Mo/yr
1. Radio-FIR SED
2. Gas reservoir + Dust/Gas
3. CO excitation, TB
4. [CII]/FIR ~ ULIRG
• Merging galaxy: Mdyn (r<2.5kpc) ~ 5e10 Mo
• Early enrichment of heavy elements and dust => star
formation started tuniv < 0.5 Gyr
• Dust formation in massive stars?
• Break-down of M- at high z?
• ‘Smoking gun’ for coeval formation of massive galaxy +
SMBH within 870 Myr of big bang?
• Consistent with ‘downsizing’ in massive galaxy and SMBH
formation (Heckman etal. 2004; Cowie et al. 1996)
LFIR vs L’(CO)
z>2
1000Mo/yr
J1148+525
z=6.42
Index=1
1e11 Mo
Index=1.7
 M(H_2) = X * L’(CO), X=4 (Milkyway), X=0.8 (ULIRGs)
 Telescope time: t(dust) = 1hr, t(CO) = 10hr