History of Cosmological History of Cosmological ReionizationReionization

• History of cosmic structure formationHistory of cosmic structure formation

• Observational constraints on Observational constraints on reionizationreionization

• Reionization process calculationsReionization process calculations

• Numerical radiative transfer simulationsNumerical radiative transfer simulations

• Detecting first galaxiesDetecting first galaxies

• ConclusionsConclusions

Renyue Cen Princeton University Observatory

@End of Dark Ages Workshop (STScI)March 14, 2006

• Adiabatic, Gaussian, scale-free density perturbation• --- Baryons 5% --- Cold Dark Matter 23% --- Dark Energy (cosmological constant?) 72%

Spergel etal (2003)

consistent with:• Inflation • Light element nucleosynthesis• q0 from SNe Ia• H0 (HST key project, SNe Ia)• Age of the universe (stellar evolution)

The Standard Cosmological The Standard Cosmological Model Model

n=0.99, 8 = 0.9, bh2=0.024,

xh2 = 0.126, H0 = 72, = 0.71

(subject to adjustments in 2 days)

WHIM

Time

Recom-bination

RealDarkAges

Pop III StarsGalaxiesQuasars1st Reion

Lya forestMajority of QuasarsEllipticals

Majority ofGalaxyClustersLSS

Redshift

z=1100 30 – 15 6 - 1 1 - 0

0.0003 13 Gyr

Cosmic Cosmic TimelineTimeline in Standard in Standard ModelModel

10-6

2nd genGalaxiesQuasarsFinal Reion

3000 K

Hierarchical structure formation ………………………………….. Log(Mnl) 105 106 108 109 1012 1014

10000 K

100K

106K

Temp

1: SDSS QSOs: neutral hydrogen fraction neutral hydrogen fraction changes from 10changes from 10-4-4 to to >10>10-2-2 from z=5.8 to 6.3 from z=5.8 to 6.3

Put Fan fig6 here

Cen & McDonald (2002) Fan et al (2002)

SDSS 1030+0524z=6.28

Observ. Constraints on Observ. Constraints on ReionizationReionization

Naïve implication: ee=0.03-0.04=0.03-0.04

More new z>6 quasars

White, Becker, Fan, Strauss (2003)

2: WMAP (12: WMAP (1stst Yr): Yr): ee=0.17 +- =0.17 +- 0.04 0.04

What does it mean?

zzriri=20=20+10 +10 -9-9

(assuming x=nHI/nHtot=0)

Bennett et al (2003)

Kogut et al. 2003

Hui & Haiman (2002)

3: Ly forest: zzriri < 9-10 < 9-10Hui & Haiman 2003; Theuns et al 2002

One viable pre-WMAP physical model: Universe Was Reionized Twice!

(Cen 2003a; Wyithe & Loeb 2003)

Solution: Prolonged Reionization Solution: Prolonged Reionization ProcessProcess

Quasar space density Star formation rate

(Haiman, Abel & Madau 2001)

log

[dlo

g [d

* * /d

t/d

t // MM

y

ryr-1-1 M

pc M

pc-3-3]]

log

[n(z

) / n

(pea

k)]

log

[n(z

) / n

(pea

k)]

redshiftredshift redshiftredshift

Z Z

0

-1

1

2

? ?

What could reionize the universe What could reionize the universe early: early: More ionizing photons wanted More ionizing photons wanted

Recent theoretical works suggest a new picture for Pop III IMF (Nakamura & Umemura 2001, 2002; Abel et al 2002; Bromm et al 2002):

Pop III IMF may be very top-heavy, possibly with most of the stars with mass >~ 100 M>~ 100 Msunsun

Abel et al (2002)

IMF for Population III (First) StarsIMF for Population III (First) Stars

Bromm et al (2002)

Tan & McKee (2002, 2004): The mass of Pop III stars is likely

to fall in the range of M = 30-100 Msun

due to stellar feedback processes

Based on abundance patterns of extremely metal-poor Galactic stars:

Oh et al. (2001), Qian & Wasserburg (2002): M>140 Msun

PISN with no r-process elements

Umeda & Nomoto (2004),Tumlinson, Venkatesan, & Shull (2004): M=10-140Msun

Type II supernovae/hypernovae

Observ. Case: Massive Pop III Observ. Case: Massive Pop III StarsStars

Ionizing photon emission Ionizing photon emission efficiencyefficiency

Pop III M*=10-300Msun: eUV=40,000-100,000 photons/baryon

Salpeter IMF Z=0.01Zsun : eUV=3500 photons/baryon

Bromm, Kudritzkl & Loeb (2001)

eUV(Pop III)/eUV(Pop II)

=10-30

= photon production rate/photon destruction rate = photon production rate/photon destruction rate

= c= c** f fescesc (df (df**/dt) e/dt) eUVUV/ C(1+z)/ C(1+z)3 3

Double peaks: one @zDouble peaks: one @z11~15-30, the other@z~15-30, the other@z22~6-10~6-10

• cc**: star formation efficiency (unknown): star formation efficiency (unknown)

• ffescesc: ionizing photon escape fraction (unknown): ionizing photon escape fraction (unknown)

• eeUVUV: ionizing photon production efficiency: ionizing photon production efficiency

• dfdf**/dt: halo formation rate (computable)/dt: halo formation rate (computable)

• C: gas clumping factor (constrained) C: gas clumping factor (constrained)

Existence of double peaks in Existence of double peaks in

A closer look: a pre-WMAP A closer look: a pre-WMAP modelmodel

Evolution of neutral hydrogen fraction

Redshift

nH

I/nH

tot &

nH

II/nH

tot

Cen (2003a)

Recent additional constraints:

Wyithe & Loeb (2004):x=a few x 10% @z~6.3based on QSO Stromgren sphere size

Mesinger & Haiman (2004,ApJ):x>=0.2 @z~6.3based on QSO Stromgren sphere size

Haiman & Cen (2005,ApJ):x=<0.25 @z~6.5based on LAE LF

Malhotra & Rhoads (2004,ApJ):x<1 @z~6.5based on LAE LF

White’s talk (2006):x~0.03 based on Stromgren sphere sizes.

Totani’s talk (2006):X < 0.6 based on GRB spectra

=0.10 +- 0.03

XHI=0.1 – 0.3@z=6-12

Evolution of the mean IGM temperature

Redshift

Mean IG

M tem

perature (K

)

Post-WMAP: implications on Pop III Post-WMAP: implications on Pop III star formation processes star formation processes

• Without Pop III massive stars: e < 0.09

• With Pop III massive stars and reasonable star formation efficiency and ionizing photon escape fraction: e =0.09---0.12

• With an inefficient metal enrichment process and Pop III massive stars: e = 0.15 possible

• To reach e = 0.17 requires either (1) ns >=1.03

or (2) c*(H2, III) > 0.01, or (3) photon escape fraction very high for Pop III

Cen (2003b)

A more detailed calculation A more detailed calculation (Wyithe & Cen 2006, astro-ph/0602503)(Wyithe & Cen 2006, astro-ph/0602503)

Redshift

fcrit/f

Jeans

• Separate treatments of halo gas and IGM in metal enrichment• Follow Pop III/II with a gradual transition determined by metals• Include photoionization feedback and minihalo screening effects

New results from this more New results from this more detailed calculation detailed calculation (Wyithe & Cen (Wyithe & Cen 2006)2006)

• Without Pop III massive stars: e < 0.05-0.06, with a rapidly increasing xHI

to >0.5 by z=8• With Pop III massive stars and reasonable star formation efficiency and ionizing photon escape fraction: e =0.09---0.12, with an extended

plateau of xHI =0.1-0.3 at z=7-12

• With perhaps too generous assumptions about Pop III star formation processes (very high escape fraction and/or very high star formation efficiency), e = 0.21 max is possible.

Which one would I bet on? Physical sanity would eliminate the last choice. Physical reasonableness for Pop III IMF would then argue for the second choice. So e =0.09---0.12 seems most likely, same as I got 4 years ago.

Judgement day: Thursday, March 16, 2006 (3rd Yr WMAP results)

A 24-billion-particle radiation transfer simulation of A 24-billion-particle radiation transfer simulation of detailed detailed cosmological reionization process (Trac & Cen cosmological reionization process (Trac & Cen 2006)2006)

Particle mass=2x106, Box size=100Mpc/h, timestep determined by cNcell=120003, Spatial resolution=8kpc comoving

Ok, bets placed, that is all fine! Ok, bets placed, that is all fine! But,But,

How much do you REALLY How much do you REALLY know know about first galaxies?about first galaxies?

A 21-cm probe of individual first galaxies

using CMB as the background radio sourcewith an antenna temperature of TCMB

T = (Ts-TCMB)(1-e-)

TCMB = 85K, TIGM=18K @z=30

The structure of a first galaxy

Threshold by X-ray Background Heating

Halo Mass

Num

ber per cubic M

pc

Brightness temperature decrement profile

Fundamental Applications with First Galaxies

• Probe IMF, nProbe IMF, nss, m, mCDM CDM , …, …

at n(gal)=1.e-6/Mpcat n(gal)=1.e-6/Mpc33 nnss=0.01 (3=0.01 (3))

• Determine PDetermine Pkk:: V=100 GpcV=100 Gpc33 within z=28-32 within z=28-32 such as baryonic oscillations, etc., without messysuch as baryonic oscillations, etc., without messy astrophysical biases astrophysical biases

• Alcock-Paczynski (AP) test:Alcock-Paczynski (AP) test: assuming each measurement 20% error,assuming each measurement 20% error, with 10,000 galaxies with 10,000 galaxies w=0.012 (3w=0.012 (3),),

if if MM=0.3 (no error) and k=0=0.3 (no error) and k=0

Abundance of 21-cm absorption halos

Square arcseconds

Mean IG

M tem

perature (K

)

Theory: MHzG~108-109Msun

Observed LAEs at z>6: SFR>40Msun/yr (Hu et al 2003;

Kodaira et al 2003),assuming c*=0.10, tsb=5x107yrs---> MLAE (total) = 1x1011Msun

Thus, the current observations of z>6 LAEs do not probe the bulk

of first galaxies;typical observed LAEs at z<6

have SFR~a few Msun/yr (Rhoads et al 2003; Taniguchi et al 2003)

Typical low high-z galaxies Typical low high-z galaxies

Cen (2003c)

(r)= 1.2x(M/0.27)-1(b/0.047)[(Rs

2-r2sin2)1/2-r cos]-1 ,where Rs and r are in proper Mpc

Rs= 4.3x-1/3(N/1.3x1057s-1)1/3(tQ/2x107yr)1/3[(1+zQ)/7.28]-1 Mpc

Cen & Haiman (2000)

Quasar Stromgren spheresQuasar Stromgren spheresCen (2003c)

(1): probing ionization state of IGM (1): probing ionization state of IGM and and sizes of Stromgren spheres sizes of Stromgren spheres

Rs=3Mpc

Rs=5Mpc

x=0.01 0.1 1.0

Evidently, (i) x=0.1 and x=0.01 differentiated at >6 level(ii) Rs determined to high accuracy; consequently,tQ determined accurately

Application of high-z galaxies Application of high-z galaxies inside quasar Stromgren inside quasar Stromgren spheresspheres

Cen (2003)

(2) galaxy luminosity function and (2) galaxy luminosity function and spatial spatial

distributions at z>6distributions at z>6

(3) probing environment around (3) probing environment around quasarsquasars

(4) probing anisotropy of quasar (4) probing anisotropy of quasar

emissionemission

… …

Application of first galaxies Application of first galaxies inside quasar Stromgren inside quasar Stromgren spheres, cont.spheres, cont.

• The universe has a long reionizationThe universe has a long reionization

process (Wyithe & Cen 2006).process (Wyithe & Cen 2006).

• The star formation processes at high-z The star formation processes at high-z

may be quite different from those for may be quite different from those for

low-z and local star formationlow-z and local star formation

• 33rdrd+…… year WMAP data should+…… year WMAP data should

give us a lot firmer informationgive us a lot firmer information

Conclusions Conclusions

• A profitable way to detect high-z galaxies A profitable way to detect high-z galaxies may be to target high-z observed luminous may be to target high-z observed luminous quasars, which provide a set of interesting quasars, which provide a set of interesting applicationsapplications

• Radio observations of 21-cm line may Radio observations of 21-cm line may provide a unique way to detect the very first provide a unique way to detect the very first galaxies at z=30-40, which could potentially galaxies at z=30-40, which could potentially provide a set of fundamental applications.provide a set of fundamental applications.