The End of the Dark Age

1
The End of the Dark Age The Formation of the
Structure of the Universe

• Jaan Einasto Enn Saar
• Tartu Observatory
• Tartu Workshop August 2005

2
Overview

• A short history of the evolution of the Universe
• Ionization history of the Universe
• Observational evidence for early evolution
• Modelling of evolution
• The growth of massive DM halos
• Formation evolution of quasars in merging
  galaxies
• Evolution of the density field
• Conclusions

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A short history of the evolution of the Universe
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Detecting The Cosmic Reionization From
High-z Quasar Spectroscopy
Djorgovski 2003
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Reionization history
Primordial Pop III massive stars and young
quasars reionize the universe at z 15 5
Their feedback may disrupt their hosts and
inhibit further massive star formation, until a
normal IMF, Pop II stars start forming, leading
to a second reionization at z 6 (Cen 2002)
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Lya Forest at z lt 5 the Universe is filled w.
ionized bubbles of H. At z gt 5 bubbles are rare
space is opaque for Lya emission
(Djorgovski 2003) Fan et al. AJ 128,
515, 2004
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High-z QSOs Are Very Metal Rich!
Solar
Dietrich, et al. 2003, ApJ 589, 722
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QSOs are more metal-rich than the DLA galaxies
at comparable redshifts or even the Milky Way
disk stars today!
QSOs
The only known stellar populations with
comparable metallicities are the cores of massive
elliptical galaxies.
disk stars
DLAs
Lu et al.
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Abundance patterns of QSO-s are similar to those
of elliptical galaxies enhanced Fe/?
Mg SNe II (massive stars) Fe SNe I (WDs)
time delay of 0.2 - 0.6 Gyr ? Start the
enrichment at z 10 !
Dietrich et al. 2003
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The mass of the BH is correlated with the
magnitude and velocity dispersion of parent
galaxies (open symbols spirals, filled
ellipticals) (Ferrarese 2004)
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Masses of bulges of galaxies/DM halos and central
black holes are closely related (Ferrarese 2004
astro-ph/0411247)
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To understand the formation and evolution of
populations of the Universe numerical analysis is
needed
The formation of Pop III stars - hydrodynamical
simulations which include neutral ionized
hydrogen hydrogen molecules neutral, singly
doubly-ionized helium etc. (Abel et al. 1998,
ApJ 508, 518) Millennium simulation with 21603
1010 particles in a cube of size 500 Mpc/h
Springel et al astro-ph/0504097 Nested sequence
of N-body resimulations to improve spatial
resolution, including molecular and atomic
cooling (Gao, White et al. astro-ph/0503003) Gala
xy merger simulation that includes radiative
cooling, star formation, BH growth, feedback from
SN and accretion onto BH (Di Matteo et al
astro-ph/0502199)
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Formation of Pop III stars
Pop III stars form in knots of filaments of early
DM structures at high redshift. (Abel et al.
1998, ApJ 508, 518)
At redshift z50 the gas density temperature in
knots grow to levels favorable to create H
molecules, H2 cooling time becomes shorter than H
recombination time. At the center of a DM-knot
(mini-galaxy) just one massive Pop III star
forms. Radiation of this star and its SN reionize
IGM preventing the formation of more Pop III
stars.
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Following the evolution
Millennium simulation has the highest spatial
resolution DM density field at z0 in a slab of
thickness 15 Mpc/h
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Environment of a rich cluster at high low
redshift. Left DM distribution Right galaxies
overlayed with DM colours of galaxies correspond
to their stellar B-V colour index. At z6
galaxies are blue, at z-0 mostly red. At the
center of the 1st ranked galaxy a quasar (BH) is
located
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The growth of massive DM halos
Using Millennium Simulation as background
hydrodynamical simulations allow to investigate
the growth of individual massive DM-halos rich
clusters of galaxies (Gao, White et al.
astro-ph/0503003).
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The growth of mass M temperature T of a massive
halo in simulation. At redshift z 40 T 104
molecular hydrogen forms and starts cooling
forming first pop III stars in nuclei of
mini-galaxies. Radiation from pop III stars
supernova explosions heats the surrounding has
and inhibits further star formation. Surrounding
gas is enriched with heavy elements. (Gao, White
et al. astro-ph/0503003)
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DM density fields at z49 and z0 centered on a
high-density peak. The size of the box is 190
times larger than the radius of the central
DM-halo. Filaments are seen at both epochs,
luminous objects form in knots. (Gao, White et
al. astro-ph/0503003)
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Formation evolution of quasars in merging
galaxies
Evolution of 2 galaxies with and w/o Black Hole.
The peak of star formation BH accretion is
reached at 1.6 Gyr. Strong wind from accretion to
BH expels gas from inner region. Remnant with BH
is spheroidal galaxy with little gas. (Di Matteo
et al astro-ph/0502199)
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Star formation rate, BH accretion rate growth
during galaxy-galaxy merger for 3 models w.
various virial velocity (mass). Dots identify
panels in previous Figure. (Di Matteo et al
astro-ph/0502199)
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The relation between final BH mass velocity
dispersion of stars of the bulge. Solid circles
show results for 6 merger simulations, open
circles show results of the same 6 mergers with
different gas fraction. Black symbols show
observational data. (Di Matteo et al
astro-ph/0502199)
Mergers lead to strong inflow that generates a
burst of star formation and feeds gas to the
supermassive BH
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Evolution of the density field
Size 200 Mpc/h 2563 particles z5 z2 z1
z0 The contraction of superclusters, the
merging of filaments in superclusters and
expansion of voids (low-density regions) is
seen JE (in prep.)
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Conclusions

• The reionization (Dark Age) can be divides into 3
  epochs
• 1) cold DA, baryon gas neutral opaque to Lya
  z gt 15
• 2) hot DA, baryon gas partly ionized, opaque to
  Lya, 6 lt z lt 15
• 3) Bright Age, baryons ionized, transparent to
  Lya, z lt 6
• The Universe was reionized twice, by Pop III
  stars SN at z15 and by Pop II stars SN at
  z6
• The formation of first Pop III stars in dense
  knots of DM (protogalaxies) starts at z50
• Pop III stars enrich the IGM, so that Pop II
  stars contain metals. Evolution chemical
  enrichment in cores of galaxies is very rapid
• Early galaxies merge giving rise to rapid growth
  of supermassive BH-s in central regions the
  accreting gas powers BH-s to quasars
• Further evolution of the structure is both by
  infall of DM and gas and by merging of galaxies