Three Modes of Metal-Enriched Star Formation in the Early ...fsgcon/abstracts_and_talks/b_smith_talk.pdf · Three Modes of Star Formation as universe evolves, T CMB decreases Z CMB

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


(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


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?


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


0.5 pcTuesday, March 9, 2010

Clump Finding


mf -6 -5 -4 -3.5 -3 -2.5 -2-3.25-3.75-4.25


mf -4 -3.5 -3 -2.5 -2-2 no CMB


Clump Finding




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.


mf -6 -5 -4 -3.5 -3 -2.5 -2-3.25-3.75-4.25

Primordial

Metallicity-reg.CMB-reg.


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)


magnetic fields?

radiation transport?

metal mixing?

non-solar abundances?

dust?

halo growth and evolution?

how about some realistic initial conditions?

If you believed that...


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)


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.


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.


Following Dust

Lagrangian tracer particles represent populations of dust.


Following Dust

Lagrangian tracer particles represent populations of dust.


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.


Duration:~ 340 yrs~ 3.86 tcc

χ = 1000vshock = 1140 km/sNo cooling

tcc = χ1/2rcloud/vshock



χ = 1000vshock = 1140 km/sNo cooling




χ = 1000vshock = 1140 km/sCooling: Z = 0.5 Z⊙




χ = 1000vshock = 1140 km/sCooling: Z = 0.5 Z⊙



Z = 0.5 Z⊙No cooling

1.8tcc

2.4tcc

3.0tcc


CAl2O3

FeFeSSi

MgOSiO2MgSiO3

Mg2SiO4

Grain Distributions: 20 M⊙ CCSN

No cooling

Z = 0.5 Z⊙

1000 km/s3000 km/s5000 km/s


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



Documents

Three Modes of Metal-Enriched Star Formation in the Early ...fsgcon/abstracts_and_talks/b_smith_talk.pdf · Three Modes of Star Formation as universe evolves, T CMB decreases Z CMB