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Three Modes of Metal-Enriched Star Formation
in the Early Universe
Britton SmithCenter for Astrophysics & Space Astronomy
University of Colorado, Boulder
First Stars and Galaxies March 9, 2010Tuesday, March 9, 2010
Collaborators
Matthew Turk (UCSD)
Steinn Sigurdsson (PSU)
Brian O’Shea (MSU)
Michael Norman (UCSD)
Devin Silvia (CU)
Mike Shull (CU)
Tuesday, March 9, 2010
How does the addition of metals alter the star-formation process?
What chemical abundance is required to form the first low-mass stars?
How rapid was the transition from Pop III to Pop II?
What was the IMF of the first generation of Pop II stars?
Is there anything else we should know?
Pop III → Pop IIa questionnaire
Tuesday, March 9, 2010
(Yoshida et al. 2006)
Atomic Cooling
Dust CoolingZ~10-5.5 Z☉
(Omukai et al. 2005;Schneider et al. 2006;Tsuribe & Omukai 2006;Clark et al. 2008)
(Bromm & Loeb 2003,Santoro & Shull 2006) Z~10-3.5 Z⊙
Pop III → Pop IIthe critical metallicity
Tuesday, March 9, 2010
take Pop III simulations, add metals, turn crank
initial conditions from O’Shea & Norman (2007)
non-eq H/He chemistry + tabulated metal cooling from Cloudy (all metals through Zn)
IC zcol log(Z/Z⊙)123
15 mf, -6, -5, -4.25, -4,-3.75, -3.5, -3.25, -3, -2.5, -2
17 mf, -4, -3.5, -3, -2.5, -224 mf, -4, -3.5, -3, -2.5, -2, -2* * - no CMB
Experimentationwhat happens when you add metals?
Tuesday, March 9, 2010
IC n nH2 Tmin log(Zcr/Z⊙)1 6.9x103 3.4 283 -4.082 3.7x103 1.9 214 -3.903 1.2x104 6.53 260 -3.85
A Zcr for Every Halo
Tuesday, March 9, 2010
0.5 pcTuesday, March 9, 2010
Clump Finding
Tuesday, March 9, 2010
mf -6 -5 -4 -3.5 -3 -2.5 -2-3.25-3.75-4.25
Tuesday, March 9, 2010
mf -4 -3.5 -3 -2.5 -2-2 no CMB
Tuesday, March 9, 2010
Clump Finding
Tuesday, March 9, 2010
Tuesday, March 9, 2010
Tuesday, March 9, 2010
Three Modes ofStar Formation
Z < Zcr: ‘primordial’ (high mass) - cooling cannot prevent loitering phase, collapse proceeds like metal-free case.
Zcr ≤ Z < ZCMB: metallicity-regulated (low mass) - cools past loitering phase, does not reach TCMB.
Z ≥ ZCMB: CMB-regulated (moderate mass) - cools rapidly to TCMB where frag. stops.
Tuesday, March 9, 2010
mf -6 -5 -4 -3.5 -3 -2.5 -2-3.25-3.75-4.25
Primordial
Metallicity-reg.CMB-reg.
Tuesday, March 9, 2010
Three Modes ofStar Formation
as universe evolves, TCMB decreases
ZCMB increases
CMB-reg. mass decreases
range of met.-reg. mode extends to higher metallicity
as z → 0, only met.-reg. mode exists
Tmin ≥ 10 K in local SF regions (z ~ 2.6)
Tuesday, March 9, 2010
magnetic fields?
radiation transport?
metal mixing?
non-solar abundances?
dust?
halo growth and evolution?
how about some realistic initial conditions?
If you believed that...
Tuesday, March 9, 2010
Dust from Pop III Supernovae
grain formation occurs on time-scales of hundreds of days.
CCSN (~10-40 M☉): ~1-2 M☉ dust.
PISN (140-260 M☉): ~15-60 M☉ dust.
variety of grain species.
lognormal size distribution with max < ~1 μm.
(Nozawa et al. 2003; Schneider et al. 2004)
Tuesday, March 9, 2010
Supernova ejecta is clumpy.
Observations of SNRs suggest that newly formed ejecta material is concentrated in high-velocity knots/clumps that have been thrown outward from the remnant’s center.
Hammel & Fesen 2008Tuesday, March 9, 2010
Reverse shock impacts ejecta with relative velocity of ~103 km/s.
The ejecta is compressed and shock-heated, leading to thermal sputtering of the dust grains.
Tuesday, March 9, 2010
Reverse shock impacts ejecta with relative velocity of ~103 km/s.
The ejecta is compressed and shock-heated, leading to thermal sputtering of the dust grains.
Tuesday, March 9, 2010
Following Dust
Lagrangian tracer particles represent populations of dust.
Tuesday, March 9, 2010
Following Dust
Lagrangian tracer particles represent populations of dust.
Tuesday, March 9, 2010
Tabulated values from Nozawa et al. 2006 for Z = Z⊙.
da
dt= −nH
msp
2ρd
�
i
Ai
�8kT
πmi
�1/2 ��ie−�iY 0
i(�i)d�i
Destroying Dust through Thermal Sputtering
Dust grains embedded in an ionized plasma are subject to thermal sputtering: high velocity ions impact the grains and knock off surface atoms.
Sputtering yields are dependent on projectile mass and thermal energy of the plasma.
Tuesday, March 9, 2010
Duration:~ 340 yrs~ 3.86 tcc
χ = 1000vshock = 1140 km/sNo cooling
tcc = χ1/2rcloud/vshock
Tuesday, March 9, 2010
Duration:~ 340 yrs~ 3.86 tcc
χ = 1000vshock = 1140 km/sNo cooling
tcc = χ1/2rcloud/vshock
Tuesday, March 9, 2010
Duration:~ 340 yrs~ 3.86 tcc
χ = 1000vshock = 1140 km/sCooling: Z = 0.5 Z⊙
tcc = χ1/2rcloud/vshock
Tuesday, March 9, 2010
Duration:~ 340 yrs~ 3.86 tcc
χ = 1000vshock = 1140 km/sCooling: Z = 0.5 Z⊙
tcc = χ1/2rcloud/vshock
Tuesday, March 9, 2010
Z = 0.5 Z⊙No cooling
1.8tcc
2.4tcc
3.0tcc
Tuesday, March 9, 2010
CAl2O3
FeFeSSi
MgOSiO2MgSiO3
Mg2SiO4
Grain Distributions: 20 M⊙ CCSN
No cooling
Z = 0.5 Z⊙
1000 km/s3000 km/s5000 km/s
Tuesday, March 9, 2010
Al2O3 C Mg2SiO4
MgSiO3 SiO2 MgO
FeS FeSi
Dust Mass Evolution: 20 M⊙ CCSN
No cooling
Z = 0.5 Z⊙
1000 km/s3000 km/s5000 km/s
Tuesday, March 9, 2010
Tuesday, March 9, 2010
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