how massive are the first stars? statistical study of the primordial star formation m popiii
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How Massive are the First Stars? Statistical Study of the primordial star formation M popIII. Variety of PopIII protostellar evolution 3 protostellar accretion paths M popIII = 10 – a few 100 M sun. ○ Shingo Hirano 1 - PowerPoint PPT PresentationTRANSCRIPT
How Massive are the First Stars?
Statistical Study of the primordial star formation MpopIII
ALMA 時代の宇宙の構造形成理論 @ 北海道大学 / Jan. 26-28, 2013
○ Shingo Hirano1
Takashi Hosokawa1, Naoki Yoshida1, Kazuyuki Omukai2, H.W.Yorke3
1University of Tokyo, 2University of Kyoto, 3JPL/Caltech
Variety of PopIII protostellar evolution 3 protostellar accretion paths MpopIII = 10 – a few 100 Msun
How Massive are the First Stars?2
Primordial HaloCosmological Simulation
z =17
Protostar Core ( ~ 0.01
[Msun] )
600 kpc/h (comving)
Accretion Phase of the Primordial Protostar
■ Different thermal evolution(main coolant is H2 molecular)
Mcloud ~ 1000 [Msun]
ZERO metallicity
■ No Metal & Dust No radiation pressure (?)
(cf, PopII, I star formation)
MpopIII ~ 1000 [Msun] (?)
UV Radiative Feedback Stalls mass-accretion
UV Radiative Feedback3
Ultraviolet (UV; hν > 13.6 [eV]) radiation from the protostar Ionizing infalling neutral gas & creating HII region Thermal pressure of the ionized region (high temperature)
is much greater than that in neutral gas of the same density
McKee & Tan (2008)
Gas on the circumstellar disk is photo-ionized & heated photo-evaporation
Growth of HII region Breakout & Expansion
Accreting star emits the ionizing UV photons
Accretion History of Protostar5
MpopIII = 43 [Msun]
moderate massive
Acc
retio
n R
ate
[Msu
n/yrs
]
… however, MpopIII depend on the initial quantities :
Primordial Star–Forming Cloud
Can be calculated byCosmological Simulations
Hosokawa et al. (2011) Radiative Hydrodynamics (RHD)
Protostar Evolution
UV radiative feedbackMass Accretion
Mstar [Msun]
Aim & Method6
Determining the initial mass distribution of the PopIII stars(massive side; in case of the single-star formation)
■ Cosmological Simulation primordial star-forming halos■ RHD + Stellar Evolution accretion histories
Cosmological Simulation
Accretion Histories
MpopIII
DistributionPrimordialGas Clouds
Cosmological Simulation
7
Cosmological Simulation8
GADGET-2 : parallel SPH+N-body code (Springel 2005)+ Primordial Chemistry (Yoshida et al. 2006, 2007)
Initial Condition : zini = 99, WMAP-7 (Komatsu et al. 2011)
+ zoom-in re-simulation technique Mresolve, init < 500 [Msun] < Mcloud
Stop calculations when the collapsing center becomes :ncen ~ 1013 [cm-3] (Lresolve ~ 10-5 ー 10-4 [pc] ~ 2 ー 20
[AU])
Nsample Lbox [kpc/h](comving)
Nzoom Lsoft [pc/h](comving)
Lsoft [pc](z=19)
msph[Msun]
7 1000 3072 6.5 0.46 0.867
98 2000 3072 13.0 0.92 6.94
Primordial Star-Forming Clouds9
108 halos @ Ncen ~ 1012 [cm-3]
3.2 r
R [pc]
NH [c
m-3]
Gao et al. (2007)
Density profiles evolve self-similarly
Infall Rate of Collapsing Cloud
Infall Rate [Msun/yrs] =
10
Menclosed [Msun]
Infa
ll R
ate
[Msu
n/yrs
]
)()(4 inf2 RvRR all
~ 10-3 – 10-1
Menclosed [Msun]
Vra
d [km
/sec
]N
H [c
m-3]
Characteristic quantities of clouds :
Protostellar Accretion Phase
11
Protostellar Accretion12
Using the setting & method in Hosokawa et al. (2011)
Radiative Hydrodynamics (RHD)
■ 2D-axsymmetric ■ Self-gravity, Hydro■ Primordial Chemistry (15 reactions with H, H+, H2, H-, e)■ Radiative-transfer : cooling, feedback■ Lcell,min ~ 25 [AU], Lbox = 1.2 [pc], Mtotal ~ few 1000 [Msun]
Protostar Evolution
Mass Accretion UV radiative feedback
* For calculating the case of the high mass accretion rate, we adopt a simple model of the stellar evolution
“Super-Giant” Protostar13
Hosokawa et al. (2012)
Mstar [Msun]R
star
[Rsu
n]Menclosed [Msun]
Infa
ll R
ate
[Msu
n/yrs
]
dM/dt > 0.04 [Msun/yrs] No KH contraction (“Super-Giant” Protostar )dM/dt > 0.004 [Msun/yrs] Ltot(M)|ZAMS > Ledd, cannot reach ZAMS
Model of “Rebound” Phase14
Hosokawa et al. (2012)
Mstar [Msun]R
star
[Rsu
n]
1
①
②2
* Ignore expansion phenomena By expansion, the effective temperature, Teff,
decreases this phase is not important for the UV radiative
feedback
Ltot ~ Ledd Scaling : Rstar //
RZAMS
Lstar // LZAMS dM/dt < 4E–3 [Msun/yrs]
Contraction to ZAMS (KH timescale)
Accretion History : one sample15
ZAMS
Mass Accretion KH Contraction ZAMS
16
Mstar [Msun]1 10 100 1000
103
102
101
104
Rst
ar [R
sun]
Accretion Histories
Mstar [Msun]1 10 100 1000
10-1
10-2
10-3
10-4Acc
retio
n R
ate
[Msu
n/yrs
]
100
Super-Giant / Rebound / Fiducial Three paths exist
17
Mstar [Msun]
1 10 100 1000
105
104
103
102
Tef
f [K
]
5000 [K]
Effective Temperature
× UV Radiation
Accretion History onto Protostar18
Mstar [Msun]1 10 100 1000
10-1
10-2
10-3
10-4
Acc
retio
n R
ate
[Msu
n/yrs
]
dM/dt > 0.04 [Msun/yrs]
dM/dt > 0.004 [Msun/yrs]
dM/dt < 0.004 [Msun/yrs]
11 / 108 … “Super-Giant” Phase36 / 108 … “Rebound” Phase61 / 108 … Become ZAMS
Hosokawa et al. (2012)
Star cannot become the Zero-Age Main-Sequence (ZAMS)
structure Omukai&Palla (2003)
KH contraction & ZAMS directly
KH contraction stage disappears entirely
Initial infall rate v.s Final MpopIII19
Good Correlation :(4πR2ρvrad)Jeans MpopIII
Simple Estimation :
MpopIII (4πR∝ 2ρvrad)Jeans
Decide MpopIII without the
calculation of accretion history(* Not consider fragmentation)
Mpo
pIII [M
sun]
(4πR2ρvrad)Jeans [Msun/yrs]
Cou
nt20
MpopIII [Msun]
Heger & Woosley’02Final fate of the non-rotating PopIII stars
■ 15 < MPopIII < 40
Core Collapse SNe ■ 40 < MPopIII < 140
Black Hole■ 140 < MPopIII < 260
Pair-Instability SNe ■ 260 < MPopIII
Black Hole
* with rapid rotationMPISN > 65 [Msun]
Chatzopoulos&Wheeler(2012)
MpopIII Distribution
32 36 21 18
Summary
■ more than 100 primordial halos showthe wide range of accretion history
■ Three type of accretion histories(1) low dM/dt KH contraction
UV radiative feedback(2) High dM/dt cannot reach ZAMS
mass accretion continues(3) HUGE dM/dt “supergiant” protostar
mass accretion continues
MpopIII = 10 – a few 100 [Msun]
□ Correlation between (4πR2ρvrad)Jeans – MpopIII
Can estimate MpopIII by using Jeans quantity
21M
popI
II [M
sun]
(4πR2ρvrad)Jeans [Msun/yrs]
Mstar [Msun]1 10 100 1000
103
102
101
104
Rst
ar [R
sun]
100