the dark age… before the stars, beyond the galaxies…
Post on 18-Dec-2015
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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
Ground State
En
erg
y
Lyman
BalmerPaschen
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Emission Lines: from Photoionization
Lymanalpha
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Energy Levels in Hydrogen
E = 0
Ground State
En
erg
yfree electron
Photo-ionization
Recombination
radiative decay
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Energy Levels in Hydrogen
E = 0
Ground State
En
erg
y To excite optical & UV lines …need at least 10.2 eV
• Hot Stars• Quasars
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Energy Levels in Hydrogen
E = 0
Ground State
En
erg
y
Hyperfine splitting of H ground state
21 cm line
E = 6 x 10 eV-6
thermally excited by collisions in cold gas
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Comparison: Hubble, Radio, very deep optical from ground
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Blue galaxies=> 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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from Jordi Miralda-Escude 2003, Science, 300, 1904
1 10 100 10001 + Z1 + Z
Age of Universe [years] 1010 109 108 107 106
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The CMB
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Gnedin’s simulation of Reionization:
log(Neutral fraction)
log(density)log T
log(mean intensity of ionizing flux)
http://casa.colorado.edu/~gnedin/GALLERY/
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Energy Levels in Hydrogen
E = 0
Ground State
En
erg
yfree electron
Photo-ionization
Recombination
radiative decay
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High Z SDSS Quasar (Fan et al 2002)
Gunn-Peterson Trough
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Lyman AlphaModerate Z Quasar
Highest Z Quasar
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Cut off fromview of opticalwavelengths !!!
nHI
nHI +nHII 10-3
If neutral fraction
>
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SquareKilometreArray
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ARRAY
Simple antenna“elements”
“Station” “Array”
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D
Sensivity depends on collecting area
Angular resolution
~ /D
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D
Sensivity depends on collecting area
Angular resolution
~ /D
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VLA
ALMAESO VLTI
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ARRAY
Simple antenna“elements”
“Station” “Array”
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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 theNetherlands
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10 arcmin
LOFAR and SKA …
QuasarQuasardistributeddistributedstar formationstar formation
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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(
neutr
al fr
act
ion
)
Ciardi & Madau 2003