Radio astronomical probes of Cosmic Reionization and the 1st luminous objects

Chris Carilli March 19, 2007 University of Colorado

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

Fan et al 2006

End of reionization?

f(HI) <1e-4 at z= 5.7

f(HI) >1e-3 at z= 6.3

TT

TE

EE

Constraint II: CMB large scale polarization -- Thompson scattering during reionization

Scattered CMB quad. => polarized

Horizon scale => 10’s deg

e = 0.09+/-0.03

z_reion= 11+/3

Page + 06; Spergel 06

Current observations => zreion = 6 to 11 (+/-3)?

Not ‘event’ but complex process, large variance time/space (eg. Shull & Venkatesan 2006)

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Fan, Carilli, Keating ARAA 06

8Mpc Gnedin03

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

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

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

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

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

1e13 Lo

2.4mJy

LFIR vs L’(CO)

M(H_2) = X * L’(CO), X=4 (Milkyway), X=0.8 (ULIRGs)

Telescope time: t(dust) = 1hr, t(CO) = 10hr

Index=1.7

Index=1

1e11 Mo

z>2

J1148+525

z=6.42

1000Mo/yr

• 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: 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 et al 2007)?

S250 = 5.0 +/- 0.6 mJy

LFIR = 1.2e13 Lo

Mdust =7e8 Mo

3’

MAMBO 250 GHz

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)

• C, O production (3e7 Mo) => Star formation started early (z > 10)?

VLA

IRAM

VLA

• Tk ~ 100K • nH2 ~ 105 cm-3

=> Typical of starburst galaxy nucleus (eg. NGC 253)

1148+52

CO Excitation

1148+5251

Radio-IR SED TD = 50 K

FIR excess = 50K dust

Radio-FIR SED follows star forming galaxy

SFR ~ 3000 Mo/yr => form large spheroid in dynamical timescale ~ 1e8 yr

Radio-FIR correlation

[CII] 158um PDR cooling line detected at z=6.4

30m 256GHz

Maiolino etal

PdBI Walter et al.

L[CII] = 4x109 Lo

L[CII]/LFIR = 3x10-4 ~ ULIRG

1”

Size ~ 0.5” (~ 2.5kpc)

SFR ~ 6.5e-6 L[CII] ~ 3000 Mo/yr

Enriched ISM on kpc scales

0.3”

J1148+52: VLA imaging of CO3-2

Separation = 0.3” = 1.7 kpc

TB = 35K => Typical of starburst nuclei

Merging galaxies?

rms=50uJy at 47GHz

CO extended to NW by 1” (=5.5 kpc) tidal(?) feature

1”

0.4”res

0.15” res

Breakdown MBH - Mbulge relation at high z: SMBH forms first?

CO FWHM + size:

Mdyn ~ 5e10 Mo

(Mgas ~ 2e10 Mo)

Expected

MBH ~ 2e9 Mo

=>Mbulge ~ 1.5e12 Mo

x1148+5251

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)

High z submm detected QSOs: Similar to low z IR-selected QSOs = star formation?

Low z IR QSOs: major mergers AGN+starburst?

Low z Optical QSOs: late-type hosts

Z~6 FIR QSOs

Z~6

ALMA reveals the cool universe: dust and gas -- the fundamental fuel for star formation

cm: star formation, AGN

(sub)mm dust, molecular gas

Near-IR: stars, ionized gas, AGN

The ALMA revolution -- observing normal galaxies into cosmic reionization: Panchromatic view of galaxy formation

LFIR = 1e11 Lo

Cosmic Stromgren Sphere

• Accurate 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? 9 z~6 QSOs with CO or MgII redshifts: <R> = 4.4 Mpc (Wyithe et al. 05; 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

Wyithe et al. 2005

=tqso/4e7 yrs

90% probability x(HI) > curve

P(>x_HI)

CSS (+ Stromgren surfaces) suggest rapid rise in f(HI) around z ~ 6 to 7?

But cf. Maselli 07: f(HI) R^-3

Cosmic ‘phase transition’?

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

Multiple experiments under-way: ‘pathfinders’ ~1e4 m^2

MWA (MIT/CfA/ANU) LOFAR (NL)

21CMA (China) SKA 1e6 m^2

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

All sky => Single dipole experiment with (very) carefully controlled systematics (signal <1e-4 sky), eg. EDGES (Rogers & Bowman 07)

140MHz

Signal II: HI 21cm Tomography of IGM Zaldarriaga + 2003

z=12 9 7.6

TB(2’) = 10’s mK

SKA rms(100hr) = 4mK

LOFAR rms (1000hr) = 80mK

Signal III: 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

Signal IV: 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 IV: Cosmic web before reionization: HI 21Forest

• 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?

159MHz

Signal V: 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

Easily rule-out cold IGM (T_s < T_cmb): signal = 360 mK

Wyithe et al. 2006

5Mpc

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…)

10’ FoV; SKA 1000hrs

Xcorrelation/Power spectral analysis in 3D – different symmetries in freq space

Freq

Signal

Foreground

Signal/Sky ~ 2e-5

TIDs – ‘fuzz-out’ sources

‘Isoplanatic patch’ = few deg = few km

Phase variation proportional to ^2

Solution:

Wide field ‘rubber screen’ phase self-calibration

Challenge II: Ionospheric phase errors – varying e- content

Virgo A VLA 74 MHz Lane + 02

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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 Rx lab); 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!

RAE2 1973

• 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

Cygnus A

1e4Jy

Cas A 1e4Jy

3C392

200Jy

3C348 400Jy

140MHz180MHz

CygA 1e4Jy

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 ?

Radio astronomy probing cosmic reionization

•‘Twilight zone’: obs of 1st luminous sources limited to near-IR to radio wavelengths

•Currently limited to pathological systems (‘HLIRGs’)

•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

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 =>

rms = 0.2 mJy

z=50

z=150

HCN emission: Dense gas directly associated with star formation

n(H2) > 1e5 cm^-3 (vs. CO: n(H2) > 1e3 cm^-3)

z=2.58

Solomon et al

index=170 uJy

J1148+52

z>2

Line sensitivity

Low order

High order, fine structure lines

The ALMA revolution Spectral simulation of J1148+5251

Detect dust emission in 1sec at 250GHz

Detect multiple lines, molecules per band => detailed astrochemistry

Image dust and gas at sub-kpc resolution – gas dynamics++

Studying 1st galaxies

Detect ‘normal’ (eg. Ly), star forming galaxies at z>6 in few hours

Determine redshifts directly from mm spectroscopy for dusty systems

z=6.55

SFR~10Mo/yr

HCN

HCO+

CO

CCH

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!

z>6 QSOs with CO and/or MgII redshifts (Wyithe et al. 05)

<z> ~ 0.08 => <R> = 4.4 Mpc