The Dark Age

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The Dark Age before the stars,
beyond the galaxies
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Overview of history of Universe
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The Dark Age
How do you study neutral hydrogen?
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??? How do you find H clouds ???
??? How do you find HI clouds ???
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Dutch Westerbork Telescope
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Comparison Hubble, Radio, very deep optical
from ground
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Energy Levels in Hydrogen
E 0
Energy
Ground State
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Energy Levels in Hydrogen
E 0
Energy
Ground State
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Energy Levels in Hydrogen
E 0
To excite optical UV lines need at least
10.2 eV
Energy
Ground State
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Energy Levels in Hydrogen
E 0
Hyperfine splitting of H ground state
Energy
21 cm line
Ground State
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Comparison Hubble, Radio, very deep optical
from ground
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Blue galaxies
gt young, massive stars
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Red galaxies
What makes them RED ???

• red stars
• redshift
• reddening (dust)

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The microwave sky (all sky picture from
WMAP
map.gfsc.nasa.gov)
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WMAP
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The microwave sky (all sky picture)
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Age of Universe years
1010 109 108
107 106
1 10
100 1000
1 Z
1 Z
from Jordi Miralda-Escude 2003, Science, 300, 1904
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The















































































































































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Gnedins simulation of Reionization
http//casa.colorado.edu/gnedin/GALLERY/
log(mean intensity of ionizing flux)
log(Neutral fraction)
log(density)
log T
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Energy Levels in Hydrogen
E 0
Energy
Ground State
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High Z SDSS Quasar (Fan et al 2002)
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Lyman Alpha
Moderate Z Quasar
Highest Z Quasar
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Square Kilometre Array
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ARRAY
Simple antenna elements
Array
Station
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Sensivity depends on collecting area
Angular resolution l/D
D
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Sensivity depends on collecting area

Angular resolution l/D
D
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VLA
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ARRAY
Simple antenna elements
Array
Station
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SKA Design
Magic Carpet
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Eggs on Legs
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LOFAR Low Frequency Array
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on map of the Netherlands
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LOFAR and SKA
distributed star formation
Quasar
10 arcmin
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LOFAR and SKA
Z 13.5 12.8
12.0 11.3 10.6
9.9 9.3
8.7 8.1
log( neutral fraction )
Ciardi Madau 2003