Dark Stars: Dark Matter annihilation can power the first stars
First Stars and Reionization
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First Stars and Reionization Andrea Ferrara SISSA/International School for Advanced Studies Trieste, Italy Five Answers for Five Questions
description
First Stars and Reionization. Five Answers for Five Questions. Andrea Ferrara. SISSA/International School for Advanced Studies Trieste, Italy. Where did the first stars form ?. First Question. Minimum Mass to Cool via H Lyα line. M inimum Mass for Self-Shielding. Minimum Mass - PowerPoint PPT Presentation
Transcript of First Stars and Reionization
First Stars and Reionization
Andrea Ferrara
SISSA/International School for Advanced StudiesTrieste, Italy
Five Answers for Five Questions
Where did the first stars form ?
First Question
Where did the first stars form ?
Minimum Massfor Collapse ( tcool = tH )
Minimum Mass toCool via H Lyα line inimum Mass
for Self-Shielding
H2 and the Radiative Feedback
Ciardi etal 2000Ciardi etal 2000
Cooling/Star formation Efficiency
z = 9
Madau, AF & Rees 2001Madau, AF & Rees 2001
fb = Mb(r < rcool)
Mb(r < rvir)
Where did the first stars form ?
Were the first stars very massive ?
Second Question
Infall Rate: 0.01 Mo/yr
Envelope: 103 Mo
Core:10-2 Mo
Salvaterra & AF 2002;Salvaterra & AF 2002;
Best fit model to NIR data:
zend = 8.8f = 4%
IR Background Data Points
Pop III stars can explain observed NIRB excess
if
VMS dominate IMF ~ (1+zend ) λLyα
PopIII Stars
Were the first stars very massive ?
Magliocchetti, Salvaterra & AF 2003Magliocchetti, Salvaterra & AF 2003
When did the transition to normal stars occur?
Third Question
Schneider, AF, Natarajan, Omukai 2002
Critical Metallicity for IMF Transition:
10-6 ZO 10-4 ZO
When did the transition to normal stars occur ?
Which stars did ionize the universe ?
Fourth Question
z = 17
NIRB Fitting Evolution
Which stars did ionize the universe ?
Ciardi, AF & White 2003Ciardi, AF & White 2003
Reionization after WMAPA Conservative Model: No “exotica”
Maximum H2/UV feedback: no stars in minihalos
Smallest star-forming halos M = 5×108 MO
Moderately heavy IMF: Larson, Mc = 5 MO
No Very Massive Stars, but metal-free
Maximum Escape Fraction, fesc = 20%
Which stars did ionize the universe ?
Ciardi, AF & White 2003Ciardi, AF & White 2003 Reionization after WMAP
z = 17.6 z=15.5 z=13.7
Larson IMF
Salpeter IMF
Which stars did ionize the universe ?
Light from First Galaxies
Optical Depth Evolution
Reconciling with GP-effectrequires a subsequent drop
of the ionizing power
No contribution to optical depth in 6 <z < 9: still within WMAP error box
Double Reionization ?
L20
Where should we look for the first stars ?
Fifth Question
Bruscoli etal 2003Bruscoli etal 2003
The IGM @ z 3: a Closer View
Temperature Metallicity
Z > Zcr
Z 0
Where should we look for the first stars ?
Scannapieco, Schneider & AF 2003Scannapieco, Schneider & AF 2003
Lyα Detection Probability
Eg Kinetic Energy / Baryon Mass into Stars
Eg Feedback Parameter
1%
3% 10%
Where should we look for the first stars ?
Summary
1. Where did the first stars form ?In Lya-cooled haloes
2. Were the first stars very massive ?Very likely, yes
3. Which stars did ionize the universe ?Normal stars, although extra contribution from massive ones
4. When did the transition to normal stars occur? Whenever/Wherever Z ~ 10 -5 ZO
5. Where should we look for the first stars ?Try hard with Lya emitters
An Emerging Scenario
Redshift0369
M/MO
<Z>/Z0
VMS/VMBH Era
Transition to Normal IMF
Normal IMF
10- 5
10- 2.5
10- 0.5
103
10- 1
100
Reionization
Required by NIRB data
Required by QSO data
High-z GRBsSNII ..
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.PopIII host candidates
SNγγ
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