Radio astronomical probes of Cosmic Reionization and the 1st luminous objects
Chris Carilli, NRL, April 2008
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: early massive galaxy and SMBH formation
Neutral Intergalactic Medium (IGM) – HI 21cm telescopes, signals, and challenges
USA – Carilli, Wang, Wagg, Fan, Strauss
Euro – Walter, Bertoldi, Cox, Menten, Neri, 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
Cosmic Reionization• Last phase of cosmic evolution to be tested • Bench-mark in cosmic structure formation indicating the first luminous structures
Barkana and Loeb 2001
Constraint I: Gunn-Peterson Effect
z
Constraint I: Gunn-Peterson Effect
Fan et al 2006
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 -- Thomson scattering during reionization
Scattering CMB local quadrapole => polarized
Large scale: horizon scale at reioniz ~ 10’s deg
Signal is weak:
TE ~ 10% TT
EE ~ 1% TT
e = 0.084 +/- 0.016
~ l/mfp ~l ne e (1+z)^2
Hinshaw et al 2008
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
Dunkley et al. 2008
GP => pushing into near-edge of reionization at z ~ 6
CMB pol => substantial ionization fraction persists to z ~ 11
Fan, Carilli, Keating ARAA 06
GP => First light occurs in ‘twilight zone’, opaque for obs <0.9 m
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)
Radio observations of z ~ 6 QSO host galaxies
Why QSOs?
Spectroscopic redshifts
Extreme (massive) systems
MB < -26 =>
Lbol > 1e14 Lo
MBH > 1e9 Mo
Rapidly increasing samples:
z>4: > 1000 known
z>5: > 100
z>6: 20
Fan 05
QSO host galaxies – MBH -- Mbulge relation
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)
Magorrian, Tremaine, Gebhardt, Merritt…
• 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?
MAMBO surveys of z>2 QSOs
2.4mJy
Dust => Gas: LFIR vs L’(CO)
non-linear => increasing SF eff (SFR/Gas mass) with increasing SFR
FIR-luminous high z QSO hosts have massive gas reservoirs (>1e10 Mo) = fuel for star formation
Index=1.5
1e11 Mo
1e3 Mo/yr
z ~ 6 QSO hosts
~ Star formation
~ Gas Mass
• Highest redshift SDSS QSO (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: Dust detection
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)?
S250 = 5.0 +/- 0.6 mJy
LFIR = 1.2e13 Lo
Mdust =7e8 Mo
3’
MAMBO 250 GHz
1148+5251
Radio to near-IR SED TD = 50 K
FIR excess = 50K dust
Radio-FIR SED follows star forming galaxy
SFR ~ 3000 Mo/yr
Radio-FIR correlation
Elvis SED
1148+52 z=6.42: Gas detection
Off channelsRms=60uJy
46.6149 GHzCO 3-2
• FWHM = 305 km/s• z = 6.419 +/- 0.001• M(H2) ~ 2e10 Mo
• Mgas/Mdust ~ 30 (~ starburst galaxies)
VLA
IRAM
VLA
Dense, warm gas: CO excitation similar to starburst nucleus
Tkin > 80 K
nH2 ~ 1e5 cm^-3
CO excitation ladder 2
NGC253
MW
J1148+52: VLA imaging of CO3-2
Separation = 0.3” = 1.7 kpc
TB = 35K => Typical of starburst nuclei, but scale is 10x larger
rms=50uJy at 47GHz
CO extended to NW by 1” (=5.5 kpc)
1”
0.4”res
0.15” res
[CII] traces PDRs associated with star formation
[CII] 158um fine structure line: dominant ISM gas cooling line
[CII] 158um at z=6.4
[CII] PdBI Walter et al.
z>4 => FS lines redshift to mm band
L[CII] = 4x109 Lo (L[NII] < 0.1 L[CII])
[CII] similar extension as molecular gas ~ 6kpc => distributed star formation
SFR ~ 6.5e-6 L[CII] ~ 3000 Mo/yr
1”
[CII] + CO 3-2
[CII]
[NII]
IRAM 30m
Gas dynamics: Potential for testing MBH - Mbulge relation at high z -- mm lines are only direct probe of host galaxies
Mdyn~ 4e10 Mo
Mgas~ 2e10 Mo
Mbh ~ 3e9 Mo =>
Mbulge ~1e12 Mo (predicted)
1148+5251 z=6.42
z<0.5
Low z IR QSOs: major mergers AGN+starburst?
Low z Optical QSOs: early-type hosts
Z~6
FIR - Lbol in QSO hosts
FIR luminous z ~ 6 QSO hosts follow relation establish by IR-selected QSOs at low z => (very) active star forming host galaxies?
Wang + 08, Hao 07
Downsizing: Building a giant elliptical galaxy + SMBH at tuniv
< 1Gyr 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
10.5
8.1
6.5
Li, Hernquist, Roberston..
z=10
• Rapid enrichment of metals, dust, molecules
• Rare, extreme mass objects: ~ 100 SDSS z~6 QSOs on entire sky
• Integration times of hours to days to detect HyLIGRs
(sub)mm: high order molecular lines. fine structure lines -- ISM physics, dynamics
cm telescopes: low order molecular transitions -- total gas mass, dense gas tracers
The need for collecting area: lines
FS lines will be workhorse lines in the study of the first galaxies with ALMA.
Study of molecular gas in first galaxies will be done primarily with cm telescopes
SMA
ALMA will detect dust, molecular and FS lines in ~ 1 hr in ‘normal’ galaxies (SFR ~ 10 Mo/yr = LBGs, LAEs) at z ~ 6, and derive z directly from mm lines.
, GBT
cm: Star formation, AGN
(sub)mm Dust, molecular gas
Near-IR: Stars, ionized gas, AGN
Arp 220 vs z
The need for collecting area: continuum
A Panchromatic view of galaxy formation
SMA
Cosmic Stromgren Sphere
• Accurate host redshift from CO: z=6.419+/0.001Ly a, high ioniz lines: inaccurate redshifts (z > 0.03)
• Proximity effect: photons leaking from 6.32<z<6.419
z=6.32
•‘time bounded’ Stromgren sphere: R = 4.7 Mpc
tqso = 1e5 R^3 f(HI)~ 1e7yrsor
f(HI) ~ 1 (tqso/1e7 yr)
White et al. 2003
Loeb & Rybicki 2000
CSS: Constraints on neutral fraction at z~6 Nine z~6 QSOs with CO or MgII redshifts: <R> = 4.4 Mpc
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 2006
ESO
OI
Not ‘event’ but complex process, large variance: zreion ~ 14 to 6
Good evidence for qualitative change in nature of IGM at z~6
Fan, Carilli, Keating ARAA 2006
ESO
OI
Saturates, HI distribution function, pre-ionization?
Abundance?
3, integral measure?
Local ionization?
Geometry, pre-reionization?
Current probes are all fundamentally limited in diagnostic power
Need more direct probe of process of reionization
Local ioniz.?
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
Experiments under-way: pathfinders 1% to 10% SKA
MWA (MIT/CfA/ANU) LOFAR (NL)
21CMA (China) SKA
Signal I: HI 21cm Tomography of IGM Furlanetto, Zaldarriaga + 2004
z=12
9
7.6
TB(2’) = 10’s mK
SKA rms(100hr) = 4mK
LOFAR rms (1000hr) = 80mK
Signal II: 3D Power spectrum analysis
SKA
LOFAR
McQuinn + 06
only
+ f(HI)
• 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
Signal III: Cosmic Web after reionization
Ly alpha forest at z=3.6 ( < 10)
Womble 96
z=12 z=819mJy
130MHz
• radio G-P (=1%)
• 21 Forest (10%)
• mini-halos (10%)
• primordial disks (100%)
Signal III: Cosmic web before reionization: HI 21Forest
• Perhaps easiest to detect
• Only probe of small scale structure
• Requires radio sources: expect 0.05 to 0.5 deg^-2 at z> 6 with S151 > 6 mJy?
159MHz
Signal IV: Cosmic Stromgren spheres around z > 6 QSOs
0.5 mJy
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
Wyithe et al. 2006
5Mpc
Prediction: first detection of HI 21cm signal from reionization will be via imaging rare, largest CSS, or absorption toward radio galaxy.
Challenge I: Low frequency foreground – hot, confused sky
Eberg 408 MHz Image (Haslam + 1982)
Coldest regions: T ~ 100z)^-2.6 K
Highly ‘confused’: 1 source/deg^2 with S140 > 1 Jy
Solution: spectral decomposition (eg. Morales, Gnedin…)
Foreground = non-thermal = featureless over ~ 100’s MHz
Signal = fine scale structure on scales ~ few MHz
10’ FoV; SKA 1000hrs
Signal/Sky ~ 2e-5Cygnus A
500MHz 5000MHz
Simply remove low order polynomial or other smooth function
Xcorr/power spectral analysis in 3D – different symmetries in freq
TIDs – ‘fuzz-out’ sources
‘Isoplanatic patch’ = few deg = few km
Phase variation proportional to ^2
Solution:
Reionization requires only short baselines (< 1km)
Wide field ‘rubber screen’ phase self-calibration
Challenge II: Ionospheric phase errors – varying e- content
Virgo A VLA 74 MHz Lane + 02
QuickTime™ and aCinepak decompressor
are needed to see this picture.
15’
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
Chippendale & Beresford 2007
• Focus: Reionization (power spec,CSS,abs)
• Very wide field: 30deg
• Correlator: FPGA-based from Berkeley wireless lab
• Staged engineering approach: GB05 8 stations Boolardy08 32 stations
C.Carilli, A. Datta (NRAO/SOC), J. Aguirre (U.Penn)
PAPER: Staged Engineering• Broad band sleeve dipole + flaps
• 8 dipole test array in GB (06/07) => 32 station array in WA (2008) to 256 (2009)
• FPGA-based ‘pocket correlator’ from Berkeley wireless lab
• S/W Imaging, calibration, PS analysis: AIPY + Miriad/AIPS => Python + CASA, including ionospheric ‘peeling’ calibration
100MHz 200MHz
BEE2: 5 FPGAs, 500 Gops/s
CygA 1e4Jy
PAPER/WA -- 4 Ant, July 2007
RMS ~ 1Jy; DNR ~ 1e4
Parsons et al. 2008
1e4Jy
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
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.
GMRT 230 MHz – HI 21cm abs toward highest z radio galaxy and QSO (z~5.2)
rms(20km/s) = 5 mJy
229Mhz 0.5 Jy
RFI = 20 kiloJy !
232MHz 30mJy
rms(40km/s) = 3mJy
N(HI) ~ 2e20TS cm^-2 ?
Building a giant elliptical galaxy + SMBH by z=6.4
Mstars=1e12Mo
MBH = 2e9Mo
• Enrichment of heavy elements, dust starts early (z > 8)
• Rare, extreme mass objects: ~ 100 SDSS z~6 QSOs on entire sky
• Integration times of hours to days to detect HyLIGRs
Destination: Moon!
RAE2 1973
No interference
No ionosphere
Only place to study PGM
Recognized as top astronomy priority for NASA initiative to return Man to Moon (Livio 2007)
NASA concept study: DALI/LAMA (NRL + MIT ++)
Limitations of measurements
CMB polarization
e = integral measure through universe => allows many reionization scenarios
• Difficult measurement (10’s degrees, uK) result
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 => First light occurs in ‘twilight zone’, opaque for obs <0.9 m
[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!
J1623
Signal I: Global (‘all sky’) reionization signature
Signal ~ 20mK < 1e-4 sky
Possible higher z absorption signal via Lya coupling of Ts -- TK due to first luminous objects
Feedback in Galaxy formation
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Furlanetto, Oh, Briggs 06
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