the dark age… before the stars, beyond the galaxies…
Post on 18-Dec-2015
214 views
TRANSCRIPT
The Dark Age…
before the stars, beyond the galaxies…
Overview of history of Universe …
The Dark Age … How do you study neutral hydrogen?
??? How do you find H clouds ???
??? How do you find HI clouds ???
Dutch Westerbork Telescope
Comparison: Hubble, Radio, very deep optical from ground
Energy Levels in Hydrogen
E = 0
Ground State
En
erg
y
Lyman
BalmerPaschen
Emission Lines: from Photoionization
Lymanalpha
Energy Levels in Hydrogen
E = 0
Ground State
En
erg
yfree electron
Photo-ionization
Recombination
radiative decay
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
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
Comparison: Hubble, Radio, very deep optical from ground
Blue galaxies=> young, massive stars
Red galaxies…
What makes them RED ???
• red stars• redshift• “reddening” (dust)
The `microwave sky’ (all sky picture from WMAP map.gfsc.nasa.gov)
WMAP:
The `microwave sky’ (all sky picture)
from Jordi Miralda-Escude 2003, Science, 300, 1904
1 10 100 10001 + Z1 + Z
Age of Universe [years] 1010 109 108 107 106
The CMB
Gnedin’s simulation of Reionization:
log(Neutral fraction)
log(density)log T
log(mean intensity of ionizing flux)
http://casa.colorado.edu/~gnedin/GALLERY/
Energy Levels in Hydrogen
E = 0
Ground State
En
erg
yfree electron
Photo-ionization
Recombination
radiative decay
High Z SDSS Quasar (Fan et al 2002)
Gunn-Peterson Trough
Lyman AlphaModerate Z Quasar
Highest Z Quasar
Cut off fromview of opticalwavelengths !!!
nHI
nHI +nHII 10-3
If neutral fraction
>
SquareKilometreArray
ARRAY
Simple antenna“elements”
“Station” “Array”
D
Sensivity depends on collecting area
Angular resolution
~ /D
D
Sensivity depends on collecting area
Angular resolution
~ /D
VLA
ALMAESO VLTI
ARRAY
Simple antenna“elements”
“Station” “Array”
SKA Design“Magic Carpet”
Eggs on Legs
LOFAR = Low Frequency Array
on map of theNetherlands
10 arcmin
LOFAR and SKA …
QuasarQuasardistributeddistributedstar formationstar formation
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