Andreas Müller Landessternwarte Heidelberg Oberseminar 2001 „Entstehung von Quasaren “

The first sources of The first sources of lightlight in the in the Early UniverseEarly Universe and the and the highest plausible redshifthighest plausible redshiftof of luminousluminous QuasarsQuasars

Andreas MüllerLandessternwarte Heidelberg

Oberseminar 2001„Entstehung von Quasaren“

OverviewOverview

* Future Instruments & Challenges ** Future Instruments & Challenges *

* Reionization Tools ** Reionization Tools *

* Gnedin Simulations ** Gnedin Simulations *

* z* zreionreion measurements * measurements *

* Reionization ** Reionization *

* The Ly* The Ly Forest * Forest *

* Cosmological Ingredients ** Cosmological Ingredients *

* The Cosmological Setup ** The Cosmological Setup *

* Primordial Objects ** Primordial Objects *

Gamov 1948: hypothesishypothesis of CBR afterglow 3K-radiation isotropic (Penzias & Wilson 1964)

Big Bang relicBig Bang relic COBE data COBE data reveal fluctuations in CMB in K domain Large scale CMB temperature anisotropy

confirmed by new instruments with higher resolution (x 30): balloon experiments

BOOMERANG, MAXIMABOOMERANG, MAXIMA Detection of seed clumps for galaxy formation

results: flat flat universe with CDMCDM cosmology

> 0> 0 ~ 0.62

B ~ 0.05 CDM ~ 0.33

HDM ~ 0.001 () tot ~ 1.0

inflation compatible

A flat A flat CDM CDM UniverseUniverse

Milestones in the Milestones in the history of the Universehistory of the Universe

Fragmentation ofFragmentation ofPrimordial ObjectsPrimordial Objects

Collapsing DM mini halos at z = 30 SPH simulations Initial mass: 2 x 106 M

Cooling via H2 chemistry from Tgas = 104 Kto the CMB floor of 86 K

Fragmentation to high-density clumps (n > 108 cm-3)

Clump growing by gas accretion and merging to 104 Mclumps first PopIII stars rather massivefirst PopIII stars rather massive!

Recently metallicity effects included:gas with higher metallicities settles into center of DM halos!

need pre-enrichment event for Z = 10-3Z

Bromm et al. 2001

Bromm et al. 2001

Gas-Clump Morphology Gas-Clump Morphology at z = 28at z = 28

30 pc

The high-mass Progenitors –The high-mass Progenitors –Protogalactic DM ClumpsProtogalactic DM Clumps

18 small blue objects collisions and merging

each in 4 Gpc distance growing

each several billion stars hierarchical structure

The Hierarchical The Hierarchical StructureStructure

z ~ 30: 11stst generation generation of stars and quasars ReionizationReionization of most H in the universe at z ~ 7 Current observations at threshold for probing

H reionization epoch! Tool: observational study of HZ sources CMB anisotropiesCMB anisotropies: small density fluctuations large-scale structure of the universe (LSS) Gravitational collapsesGravitational collapses in dense regions clumpy structure Constraint by observations: evolution of galaxies at z < 6 Elementary building blocks: 1st gaseous objects with Jeans Jeans

massmass (~ 104 M) formed in SCDM models at z ~ 15-30 Evolution of the Universe:

homogeneous, isotropic, simple clumpy, complicated

Simple setupi) primordial power spectrum of Gaussian density fluctuationsii) DM mean densityiii) initial temperature and density of cosmic gasiv) primordial composition by Big Bang nucleosynthesisv) lack of dynamically-significant magnetic fields

Analytics: early evolution of seed density fluctuations Numerics: collapse and fragmentation of nonlinear structure Tools: HD simulations, SPH, N-Body, Radiative Transfer 11stst light light from stars and quasars ended the “dark ages” (Rees)

of the universe renaissance of enlightenmentrenaissance of enlightenment Reionization epochReionization epoch

The Cosmological The Cosmological IngredientsIngredients and Numerics and Numerics

LyLy Forest & Reionization Redshift Forest & Reionization Redshift

firstionisators

emanatingHII regions

overlappingbubbles

Gunn-Peterson trough

~ 105

transmittedflux

c = 912 Aabsorption by photoionization of H and He

lookback time

= 1216 A = 1026 A

Optical spectrum of Quasar with z = 5.8Optical spectrum of Quasar with z = 5.8

Fan et al. 2000

observational diagnosis:

Universe is fully ionizedfully ionized at z = 5.8!

When and how was the IGM ionized?When and how was the IGM ionized?

Key ingredients Key ingredients for Reionizationfor Reionization

Need: intergalactic ionizing radiation field Radiative FeedbackRadiative Feedback

Sources/Ionisators: escape radiation of

first stars & Quasarsfirst stars & Quasars current reionization models with isotropic point

sources (Gnedin 2000, Miralda-Escudé et al. 1999) Sources embedded in densest regions (haloshalos) Constraint: reionization simulation resolution Simplification: point sources in large-scale IGM! Challenges:

clumpinessclumpiness (radiation affected strongly by inhomogeneous effects)

HD feedbackHD feedback (winds, SN)

Ionization fronts Ionization fronts in the IGMin the IGM

radiation of first ionisators HII bubbles HII bubbles (Strömgren spheres)H ionization threshold: 13.6 eV

Stellar ionizing spectrum: most photons above threshold;CS high thin HI layerthin HI layer suffices to absorb all photons!

no He contributions! Model assumptions: sphericalspherical ionized volume RecombinationRecombination very high in high-density clumps MaximumMaximum comoving radiuscomoving radius (neglect recombination,

SCDM: B ~ 0.045, M ~ 0.3, ~ 0.7; N: ionizing photons

per baryon, Nion: ionizations per baryon, M: halo mass,

n0H: present number density of H) :

Loeb et al. 2000

Reionization of Hydrogen Reionization of Hydrogen in the IGMin the IGM

I I initial pre-overlap stageinitial pre-overlap stage

individual sources

escape photons find their way through high-density regions (high recombination rate!)

IGM is two-phase medium

highly ionized regions

neutral regions

ionization intensity very inhomogeneous


II II rapid overlap phase of rapid overlap phase of reionizationreionization

higher exposition by ionizing photons!

ionization intensity increases rapidly

expansion into high-density gas

several unobscured sources

ionization intensity more homogeneous


II II moment of reionizationmoment of reionization

ionization radiation does NOT reach self-shielded, high-density clouds

end of overlap phase

IIIIII post-overlap phasepost-overlap phase

This continues indefinitely, since collapsed objects retain neutral gas even in present universe.

Milestone at zbr = 1.6

““breakthrough redshift”breakthrough redshift”

Below zbr all ionizing sources are visible!

Above zbr absorption by Ly forest clouds

Only sources in small redshift range are visible!



Expanding HII region around an isolated source

Scalo et al. (1998)

Vmax = 4/3rmax3

solid: source switch-on @ z = 10

dashed: source switch-on @ z = 15

C = 0

C = 1

C = 10

Evolution of Evolution of filling factorfilling factor

Nion = 40

clumping factor C = const

dashed: collapsefraction Fcol

dotted: obs. lower limit for zreion (Fan et al. 2000)

C = 0

C = 10

C = 30

C = 1

z ~15 Recombination

less important at HZ!

Loeb et al. 2000

ConsequencesConsequences

Star-forming galaxies in CDM hierarchical models can explain reionization of the universeat z ~ 6 – 15

Further contributes for ionization by mini-quasarsmini-quasars is possible

uncertain parameters for determining zdetermining zreionreion:

Source parametersSource parameters

formation efficiency of stars and quasars escape fraction of ionizing sources Clumping factor C depends on the density

and clustering of the sources source halos form in overdense regions C depends on sources and IGM density

Gnedin 2000 -Gnedin 2000 - StellarStellar Reionization SimulationsReionization Simulations

CDMCDM with m = 0.3 radiative transfer code periodic boundary conditions 1283 DM, 1283 baryonic particles (mb = 5x105 M) thin slices through a Mpc box with 4 h-1 per side J21: mean ionization intensity at Lyman limit

(in units of 10-21 erg cm-2 s-1 sr-1 Hz-1) J21 inside HII regions depends on absorption and RT

through IGM includes local optical depth effects does notdoes not include shadowing

SetupSetup

Gnedin 2000Gnedin 2000Reionization SimulationsReionization Simulations

z = 11.5z = 11.5

log of HIfraction

redshift evolutionof log from mean ionization density

gas temperaturegas density

Gnedin 2000 Gnedin 2000 Reionization SimulationsReionization Simulations

z = 9.0z = 9.0

z = 7.7z = 7.7


z = 7.0z = 7.0


z = 6.7z = 6.7


z = 6.1z = 6.1


z = 5.7z = 5.7


z = 4.9z = 4.9


ionized bubbles emanate from main concentrations of sources

sources located in highest density regions (C ~100) bubbles expand in low density regions in IGM finally bubbles overlap complex topology of ionized regions neutral islands remain in highest density regions But: rough approximations in RT have to be treated

more accurately and then explored in detail

ResultsResults

Gnedin 2000 -Gnedin 2000 - StellarStellar Reionization SimulationsReionization Simulations

QuasarQuasar ReionizationReionization

bright point-source HII funnel HII funnel (in disk) photons escape through channel!

hard quasar photons penetrate deeper into neutral gas thicker ionization frontthicker ionization front

Quasar X-photons catalyze HH22 molecule molecule formation stars form in tiny halos stars form in tiny halos (Haiman, Abel & Rees, 1999)

BUT: BUT: hardness of ionization spectrum depends of initial mass function!

vs. vs. StellarStellar ReionizationReionization

The Loeb-Rybicki The Loeb-Rybicki halohalo Diffuse Ly halos due to Hubble expansion Tool for probing distribution and velocity field of

neutral IGM before epoch of reionization Disappearance of Ly halos signals zreion !

Detection challenge:low surface brightness!

NGST

21cm tomography 21cm tomography in the pre-reionization epochin the pre-reionization epoch

Hyperfine structure transitionHyperfine structure transition: spin-flip from triplet to singlet state traces HI regions

Observability:Observability: ground-state thermalizes with CMB perturbation of thermal equilibrium by collisions

and scattered Ly photons map redshifted 21cm emission at HZ to reveal

neutral pre-ionization IGM (pre-overlap stage I)

Instruments: Square Kilometer Array (SKA)Square Kilometer Array (SKA)

The Evolution The Evolution of the SFRof the SFR

Barkana & Loeb 2000

z reio

n =

6

z reio

n =

8

z reio

n =

10

SFR = 10%(obs. indicated)

upper: total SFR

lower: NGST fract.

flim = 0.25 nJy

Blain et al. 1999

Reionization

Reheating

Suppressed SFR

He - ReionizationHe - Reionization HeI He II by 24.6 eV photons He II ionization threshold @ 54.4 eV Reionization of He II later (lower z!) than HI

He - Reionization more observable! („H preview“)He - Reionization more observable! („H preview“) nH/nHe ~ 13: He more rare no prob!

Observational probe:heating of IGMheating of IGM due to hard ionisators H reionization: TIGM ~ 104 K

He reionization: TIGM > 2 x 104 K hotter IGM suppresses dwarf galaxy formation TIGM measurements:

search for smallest line-widthssmallest line-widths among H Ly absorption lines

Schaye et al. 2000: isothermal IGM with T ~ 2 x 104 K @ z = 3

gray shading: theoretical with HI Ly forest

HST data

He II LyHe II Ly absorption in the IGM – absorption in the IGM –Q 0302-003 z = 3.286Q 0302-003 z = 3.286

Heap et al. (2000)

~ 1.9 ~ 4.0 ~ 4.5 - 5.0

pro

xim

ity e

ffect

conta

min

ati

on

em

iss i

on

He II Ly forest

Ly absorption by intergalactic He II fits data for low-density IGM

sharp opacity break at z = 3.0 ( ~ 1240 A) sudden hardening of UV ionizing

background below z = 3 high opacity only requires ~0.1% of

He not fully ionized

confirmation by indirect diagnosis: Si-4/ C-4 ratioSi-4/ C-4 ratio(Songaila & Cowie 1996, Songaila 1998)

Q 0302-003 Q 0302-003 - Interpretation- Interpretation

Overlap phase of full He reionization Overlap phase of full He reionization at higher z!at higher z!

NCSA simulationNCSA simulationNorman et al. 1997

Numerical hydrodynamics simulation of the Ly forest

gas density distribution at z=3

CDM spectrum of primordial density fluctuations

H0 = 50 km/s comoving box size of 9.6 Mpc b = 0.06 ( 76% H, 24% He) cube side 2.4 Mpc (proper) Isosurfaces: baryons at ten

times meancosmic density

Tgas = 3 x 104 K (dark blue) Tgas = 3 x105 K (light blue)

single random slice through cube shows baryonic overdensity represented by a rainbow--like color map (black=min to red=max)

HeII mass fraction: wire mesh in same slice (fine structure)

fine structure in minivoids: rescaled mass fraction inoverdense regions by gas overdensity wherever it exceeds unity.

The Reionization The Reionization ChallengeChallenge How much ionizing sources are available?

ExtrapolationExtrapolation from observed populations of galaxies and quasars to HZ (Madau et al. 1999,

Miralda-Escudé et al. 2000)

Conclusion:Conclusion:HZ source population is similar to the one

observed at z ~ 3 – 4 and suffices to produce the J21 needed!

But: But: ? Escape fraction ?

? Luminosity function ?? Clumping factor ?? Recombination ?

WANTED! further constraining observations WANTED!

Future Future InstrumentsInstruments Observational efforts to dive into HZ regime:

further space-telescopes & large ground-based telescopes (optical: 30 m diameter; radio: SKASKA)

NGSTNGST (launch 2009 planned)sub-nJy sensitivity in IR range (1-3.5m)probing optical-UV sources at z > 10

Popular CDM models predict 1st baryonic objects at z ~ 10

Future: change focus from

LSSLSS (Large Scale Structure) to

SSSSSS (Small Scale Structure) Waiting for observational inputobservational input data from

NGST, MAPNGST, MAP, Planck,Planck, CAT, CBI & SKACAT, CBI & SKA Next decade: high precision cosmology

SummarySummary

* Primordial Objects at z ~ 30 *

* Ly Systems probe Reionization epoch z ~ 7 *

* Tune and Refine Simulations *

* Constraints by Observational Input *

* Cosmology in the 21. Century: SSS *

* Reionization studies by LR halo, 21cm, SFR counts *

ReferencesReferences

Loeb astro-ph/0010467, 0011529 Gnedin astro-ph/0002151, 0008469, 9909383 Fan astro-ph/0005414 Heap ApJ 534, 69-891 (2000) Schaye astro-ph/9912432 Bromm astro-ph/9910224, 0103382, 0104271

URLs:http://casa.colorado.edu/~gnedinhttp://cfa-www.harvard.edu/~Loebhttp://www.hep.upenn.edu/~max/index.htmlhttp://background.uchicago.edu/~whuhttp://zeus.ncsa.uiuc.edu:8080/LyA/minivoid.html

Andreas Müller Landessternwarte Heidelberg Oberseminar 2001 „Entstehung von Quasaren “

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