History of Cosmological Reionization History of cosmic structure formation Observational constraints on reionization Reionization process calculations Numerical radiative transfer simulations Detecting first galaxies ConclusionsRenyue 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 Model n=0.99, s8 = 0.9, Wbh2=0.024, Wxh2 = 0.126, H0 = 72, L0= 0.71(subject to adjustments in 2 days)WHIM

Time Recom-binationRealDarkAgesPop III StarsGalaxiesQuasars1st ReionLya forestMajority of QuasarsEllipticalsMajority ofGalaxyClustersLSS Redshiftz=110030 156 - 11 - 00.000313 Gyr Cosmic Timeline in Standard Model 10-62nd genGalaxiesQuasarsFinal Reion3000 KHierarchical structure formation .. Log(Mnl) 105 106 108 109 1012 101410000 K100K106KTemp

1: SDSS QSOs: neutral hydrogen fraction changes from 10-4 to >10-2 from z=5.8 to 6.3Put Fan fig6 here

Cen & McDonald (2002)Fan et al (2002)SDSS 1030+0524z=6.28Observ. Constraints on ReionizationNave implication: te=0.03-0.04

More new z>6 quasarsWhite, Becker, Fan, Strauss (2003)

2: WMAP (1st Yr): te=0.17 +- 0.04

What does it mean? zri=20+10 -9(assuming x=nHI/nHtot=0) Bennett et al (2003)Kogut et al. 2003

Hui & Haiman (2002)3: Lya forest: zri < 9-10

Hui & Haiman 2003; Theuns et al 2002

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

(Cen 2003a; Wyithe & Loeb 2003)

Solution: Prolonged Reionization Process

ZZ0-1 1 2?? What could reionize the universe early: 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 Msun Abel et al (2002)IMF 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 Msundue to stellar feedback processes

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

Oh et al. (2001), Qian & Wasserburg (2002): M>140 MsunPISN with no r-process elements

Umeda & Nomoto (2004),Tumlinson, Venkatesan, & Shull (2004): M=10-140MsunType II supernovae/hypernovae

Observ. Case: Massive Pop III Stars

Ionizing photon emission efficiency

Pop III M*=10-300Msun: eUV=40,000-100,000 photons/baryon Salpeter IMF Z=0.01Zsun : eUV=3500 photons/baryonBromm, Kudritzkl & Loeb (2001)eUV(Pop III)/eUV(Pop II)=10-30

h = photon production rate/photon destruction rate = c* fesc (df*/dt) eUV/ C(1+z)3 Double peaks: one @z1~15-30, the other@z2~6-10

c*: star formation efficiency (unknown)fesc: ionizing photon escape fraction (unknown)eUV: ionizing photon production efficiencydf*/dt: halo formation rate (computable)C: gas clumping factor (constrained) Existence of double peaks in h

A closer look: a pre-WMAP modelEvolution of neutral hydrogen fractionRedshiftnHI/nHtot & nHII/nHtot 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=

Evolution of the mean IGM temperatureRedshiftMean IGM temperature (K)

Post-WMAP: implications on Pop III star formation processes Without Pop III massive stars: te < 0.09 With Pop III massive stars and reasonable star formation efficiency and ionizing photon escape fraction: te =0.09---0.12 With an inefficient metal enrichment process and Pop III massive stars: te = 0.15 possible To reach te = 0.17 requires either (1) ns >=1.03 or (2) c*(H2, III) > 0.01, or (3) photon escape fraction very high for Pop IIICen (2003b)

A more detailed calculation (Wyithe & Cen 2006, astro-ph/0602503)Redshiftfcrit/fJeans 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 detailed calculation (Wyithe & Cen 2006) Without Pop III massive stars: te < 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: te =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), te = 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 te =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 detailed cosmological reionization process (Trac & Cen 2006)Particle mass=2x106, Box size=100Mpc/h, timestep determined by cNcell=120003, Spatial resolution=8kpc comoving

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

How much do you REALLY know about first galaxies?

A 21-cm probe of individual first galaxiesusing CMB as the background radio sourcewith an antenna temperature of TCMB dT = (Ts-TCMB)(1-e-t)

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

The structure of a first galaxy

Threshold by X-ray Background HeatingHalo MassNumber per cubic Mpc

Brightness temperature decrement profile

Probe IMF, ns, mCDM , at n(gal)=1.e-6/Mpc3 Dns=0.01 (3s)

Determine Pk: DV=100 Gpc3 within z=28-32 such as baryonic oscillations, etc., without messy astrophysical biases

Alcock-Paczynski (AP) test: assuming each measurement 20% error, with 10,000 galaxies Dw=0.012 (3s), if WM=0.3 (no error) and k=0Fundamental Applications with First Galaxies

Abundance of 21-cm absorption halosSquare arcsecondsMean IGM temperature (K)

Theory: MHzG~108-109MsunObserved LAEs at z>6: SFR>40Msun/yr (Hu et al 2003;Kodaira et al 2003),assuming c*=0.10, tsb=5x107yrs---> MLAE (total) = 1x1011MsunThus, the current observations of z>6 LAEs do not probe the bulkof first galaxies;typical observed LAEs at z

t(r)= 1.2x(WM/0.27)-1(Wb/0.047)[(Rs2-r2sin2q)1/2-r cosq]-1 ,where Rs and r are in proper MpcRs= 4.3x-1/3(N/1.3x1057s-1)1/3(tQ/2x107yr)1/3[(1+zQ)/7.28]-1 MpcCen & Haiman (2000)Quasar Stromgren spheresCen (2003c)

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

Rs=3MpcRs=5Mpcx=0.01 0.1 1.0Evidently, (i) x=0.1 and x=0.01 differentiated at >6s level(ii) Rs determined to high accuracy; consequently,tQ determined accuratelyApplication of high-z galaxies inside quasar Stromgren spheresCen (2003)

(2) galaxy luminosity function and spatial distributions at z>6 (3) probing environment around quasars (4) probing anisotropy of quasar emission Application of first galaxies inside quasar Stromgren spheres, cont.

The universe has a long reionization process (Wyithe & Cen 2006). The star formation processes at high-z may be quite different from those for low-z and local star formation

3rd+ year WMAP data should give us a lot firmer information

Conclusions

A profitable way to detect high-z galaxies may be to target high-z observed luminous quasars, which provide a set of interesting applications Radio observations of 21-cm line may provide a unique way to detect the very first galaxies at z=30-40, which could potentially provide a set of fundamental applications.

top row: 1/1000 of a box volume from z=100, to z=18.2middle row: z=18.2 only and continuously zoom inbottom row: z=18.2 only top row: 1/1000 of a box volume from z=100, to z=18.2middle row: z=18.2 only and continuously zoom inbottom row: z=18.2 only T=300 K due to H2 coolingAnd n=1.e-4 /cm^3, the critical densityOf H2 rotational-vibrational line cooling,Yields total core mass of 10^3 Msun.These cores collapse inside-out to formA protostar, which then grows rapidlyIn mass, through accretion in a disk.

Below 30Msun feedback is not importantBut above 100Msun feedback becomesThe bottleneck due to (1) HII regionBreakout to large distances whereEscape velocity equals the theSound speed of 10km/sAnd (2) Lyman-alpha and FUV pressureIn the HII region.M>140 Msun: PISN after core He depletion(Hedge and Woosley 2002), explosive O and SiBurning . This instability quickly disrupts. The star, ejects metals and leaves no remnant. Because it is triggered at an unusually Early stage in the stars evolution. This PISN produces an unusual nucleosynthetic signature, which could appear in the second generation EMP (extremely metal poor) stars in the Galactic halo. Qian Wasserburg (2002) and Oh et al. (2001) used this idea to argue that these stars justify the VMS hypothesis.When M>260Msun, as the temperatures Resulting from PI collapse are great enoughTo photodisintegrate nuclei, which counters explosive oxygen and silicon burning (Fryer, Woosley & Heger 2001; Heger & Woosley 2002). Little mass ejection and metal enrichment from such supernovae.M=40-140: form BHs with relatively inefficient metal ejection.M100): these elements are thought to be produced by rapid neutron capture in hot, dense, neutron-rich environments during explosive events. Associated with stars M=8-40Msun. The absolute abundances and relative ratios of r-process elements are thus sensitive indicators of core-collapse supernova activity.The mean [r/Fe] is similar to the solar value at all [Fe/H], but with up to 2 dex scatter at [Fe/H]~-3. The relative abundances (i.e., [Eu/Ba] are also similar to the solar values.Primary elements (C,N,O): of these direct products of main-sequence stellar nucleosynthesis, C is easily found in EMPs, but N and O are difficult to measure.Many EMP stars are C-rich relative to Fe.

Tumlinson et al. (2004 argue that VMS have no significant post-He nuclear burning and therefore produce no r elements (HW02). If VMS produce all the Fe up to [Fe/H]~-3, the r elements should be absent instead of appearing at [r/Fe]~ -0.5 as observed.

Wasserburg & Qian (2000) argue that the qualitative change in [r/Fe] at [Fe/H]~-3 presented an ``iron conundrum; namely, that the wide dispersion in Eu and Ba abundances at [Fe/H}~-3 suggested unrelated sources of Fe and r elements. They proposed a prompt (P) inventory of Fe production by an initial propulation with large Fe yields but little or no r production. This initial inventory ceased at [Fe/H]~-3, where the onset of high-frequency (H) events (SN II, tau~10^7 yrs) and low-frequency (L) events (SN Ia, tau~10^8yrs) initiated a correlation between r and Fe.

Oh et al. (2001) pointed out that the trends in [Fe/H] and Ba also appear in Si and Ca, elements produced by PISN, but not in C, which is not abundantly produced by PISN, apparently strengthening the positive evidence that VMS dominated metal enrichment from the first stellar generation.