恒星進化の理論の現状 とアストロメトリ
DESCRIPTION
『 高密度アストロメトリ観測時代を迎えた21世紀の天文学 』 (国立天文台、 Sep. 19-20 、 2007 ). 恒星進化の理論の現状 とアストロメトリ. 藤本正行 須田拓馬・勝田豊(北大理) 小宮悠(東北大理). contents. Parallaxes ⇒ 距離 ⇒ 光度 + spectroscopy → 恒星の半径、表面温度、質量、組成 ⇒ Age-Metallicity relation ⇒ star formation history of solar neighborhood 2. 恒星進化の理論的課題 - PowerPoint PPT PresentationTRANSCRIPT
恒星進化の理論の現状とアストロメトリ
藤本正行須田拓馬・勝田豊(北大理)小宮悠(東北大理)
『高密度アストロメトリ観測時代を迎えた21世紀の天文学』(国立天文台、 Sep. 19-20、 2007)
contents
1. Parallaxes ⇒ 距離 ⇒ 光度 + spectroscopy → 恒星の半径、表面温度、質量、組成
⇒ Age-Metallicity relation ⇒ star formation history of solar neighborhood
2. 恒星進化の理論的課題– Mass Loss – Internal (Extra) Material Mixing ~ convective overshooting 非球対称効果( rotation, magnetic fields)
3. 銀河系の構造・進化への探査手段としての恒星– 惑星を持つ恒星( Planet Hoboring Stars PHS )– 銀河系ハロー星( Extremely Metal-Poor Stars EMP, UMP, EM
P )
1. HR diagram from Hipparcos
near-by stars
Hyades
Model fitting (Perryman et al. 1998, A&Ap)
ZAMS:Metallicity and effective temperature
from high resolution spectroscopy: [Fe/H]= 0.14Solar mixing length: l=1.64
resultant helium abundance: Y = 0.26Isochrones: Age 625 ±50 Myr
Asplund, Grevesse & Sauval . (2004)Decrease of metal abundance in solar by almost a factor of two as compared with a compilation by Anders & Grevesse (1989)
Physical parameters
for Evolved stars(de Silva et al 2006 A&A)
Mass-metallicity relation
Age-metallicity relation
Color-Magnitude Diagram
Star Formation History of solar neighborhood
(Cignoni et al 2006 A&A)
CMD of near-by stars
LuminosityFunction
SFR vs. Agewith the evolutionary models
2. 恒星進化の理論的な課題2.1 mass loss
1) Massive Stars
⇒ Supernova
neutron stars
black hole
2) Intermediate- & Low-mass Stars
⇒ white dwarfs
2.1.a Mass loss from Massive Stars
Wolf Rayet WNL
WC
Limongi & Chieffi ( 2006 )
wind mass loss
by the central exhaustion of helium
SN ExplosionsCore Mass at SNe
ηcarina (binary)
VY Cannis Majoris
Wolf-Rayet Stars WR124
WR 104 (binary)
2.1.b Low- & Intermediate mass stars -- from AGBs to PNe and to WDs
Born-again AGBIgnition of Very Late Thermal Pulse Hydrogen is mixed and burnt by He-flash convection
Fast wind Super wind
Hydrogen deficientCSPNe ~20%
Non-DA (hydrogen deficient)WDs ~20%
Herwig 2005, ARA$AP
Wind mass loss
End of Low- and Intermediate –mass stars
Cat Eye Planetary Nebulae
X-ray from PNe
Guerrero, Chu & GruendlMem. S. A. It. 76,446 (2005)
Suzaku observation of BD+30°3639
Murashima, Kokubun, Makishima et al. 2006, ApJL,647, L131村島未生、天文学会 2006 年春季年会講演
Large enhancement ofC and Ne
Fast wind ejects the matter from the Helium Flash Convective Zone
X-ray spectra from BD +30°3639
XIS-1 spectra background
Spectra with the solar abundance ratio
Empirical Mass Loss Rates
Reimers formula (1977)
Nieuwenhuijen & Jager (1990)
Fast wind
Mass Loss Theory (Massive Stars)
(A&A, 2000)
Radiation Pressure (Line-Driven)
+ Multiple Scattering
may subject to Large overestimation by Clumps in Wind (Bouret etal. A&A 2005)
Foullerton et al. ApJ 2006
(mass loss rate d∝ 1.5)
eg.,
Mass Loss Theory; Cool starsPulsation-driven wind model
+ Radiation Pressure on DustsCarbon-rich Chemistry
(Watcher et al. A&A, 2002)
But, for Oxygen-rich Chemistry; Shortage of radiation pressure on dusts (Woitke A&A, 2006)
RGB
+Superwind
+AGB
Large Mass Loss at Later Stages
4 210 , 10L L R R
4 210 , 10L L R R
Reimers formula
Mira variables
Fast wind
Lawlor & MacDonald 2006
1R R 4 210 , 10L L R R
(Pulsation period)
2.2 Mixing in Stars
Current standard framework = spherical symmetry + thermal convection +
chemical diffusion (mixing length theory)Rotation, magnetic fields ⇒ instabilities = turbulence ⇒ transport of Angular momentum + internal material mixing
Results
1.0Msun
0.8Msun
log Teff
Log
(L
/Lsu
n)Surface metal pollution shifts the evolutionary track to the lower effective temperature.
Z=0.02
Polluted: Z=0.02 at interior,Z=0.04 at Surface convection
Z=0.04
He enriched model
0.90 He enrichedM
1.01
1.00 Basic modelM
1.09M
Z=0.04, homogeneous
ZAMS for Basic modelZAMS for He-enriched model
log Teff
Log
(L
/Lsu
n)
Mixing-length enlarged model
1.00 Basic modelM
1.09M
0.98 Mixing-length enlargedM
1.10M
ZAMS for Basic modelZAMS for Mixing-Length enlarged model
log Teff
Log
(L
/Lsu
n)
Ages of basic model and other models
Age of the basic model [Gyr]
Age
of
chan
ged
free
-par
amet
er m
odel
s [G
yr]
Ages of He enriched and large mixing-length models are underestimated if treated as a basic model.
He enriched
Mixing-length enlarged
1:1
3. Stellar Evolution as a Probe3.1 PHS with Hot Jupiters
PHS
Stars withoutplanets
Extra-solar planets discovered
質量の分布 軌道半径と離心率
( 1 AU= 地球の軌道半径)(1 MJUP =木星の質量)
○ 惑星の母星
10
10 sun
[Fe/H]=log (Fe) / (H)
log (Fe) / (H )
X X
X X
恒星の金属量
Arguments against Metal-Pollution
Polluted?
Ecuvillon et al. (2006)
No-correlation with the depthof surface convection
No or weak correlation s with the condensation temperatures
Giants with PlanetsPlanets with Giants are metal-poorer than those with Dwarfs (Pasquini et al. 2007)
Metallicity Distribution & Metal-Age relation
Giant PHSs (G and K)
Dwarf PHSs
Possible explanations
1) Formation mechanism depending on the mass of host stars
2) Metal dependence of
Migration: metal-rich host smaller orbits
3) Surface pollution ∵ dilution due to deep
surface convection
3.2 Stars in the Galactic HaloDeep survey of metal-poor stars in the Galactic Halo:
HK survey ( Beers et al. 1992 ) [2800 deg2 (North) + 4100 deg2 (South),
11.0 < B < 15.5 ]
Hamburg/ESO (Christlieb et al. 2000) [8225 deg2 (South), 10.0 < B < 17.5 ]
[Fe/H]<-2 の星 ~2700 個 [Fe/H]<-3 の星 ~400 個
(Beers et al. ARA&Ap 2005)
~ -5 -5 ~ -4 -4 ~ -3 -3 ~ -21
10
100
1000
10000
num
ber
[Fe/H]
effective yields
HK
HAM/ ESO
Beers & Christlieb (2005) + Norris et al. (2007)
2 stars below [Fe/H] <-5, HE0107-5240 ( -5.3, 2003) HE1327-2426 (-5.4, 2005)1 star between [Fe/H] = -4 ~-5 HE0557-4840 (-4.8, 2007)
3.2.1 EMP population の IMF と Binary origin ( Komiya et al. 2007 )
EMP star として残る
白色矮星 +CEMP 超新星
鉄 , r-process 元素合成
低質量星 中質量星 大質量星
主星の IMF
伴星の伴星の IMFIMF
Mmd=10 M, Δm=0.4 とすると
mξ(m)
m (M)0.1 1 10 100
Binary Binary ― Probe into missing more massive ― Probe into missing more massive EMP stars―EMP stars―
H
C,O
H
He
Estimate of the IMF
CEMP star is formed in a binary system.
Evolution of a primary star affects abundances of a secondary star.
Observed feature of a CEMP star
Mass of a primary star.
2 種類の CEMP
CEMP-s
s-process 元素過剰窒素も過剰
CEMP-nos
s-process 元素は少ない窒素は過剰な星と過剰でない星がある( EMP ではない炭素星は 1 種類)
[Ba/
Fe]
-1 -0.5 0 0.5 1 1.5 2 2.5 3
□ : [C/Fe], ■:[N/Fe]
3
2
1
0
-1
-2
CEMP-nos
CEMP-s
3.2.2 Metallicity Distribution Function (MDF)
Derived top-heavy IMF is consistent with observation (for [Fe/H] > -4).
One zone model.No infall/outflow.Instantaneous recycling.
Fe yield: 0.07M☉
1
10
100
1000
10000
100000
-6 -5.5 -5 -4.5 -4 -3.5 -3 -2.5 -2
nu
nm
be
r
[Fe/H]
Number
10000
1000
100
10
1
[Fe/H]
Salpeter IMF
Theoretical MDF for IMF with Mmd
=10 M .☉
observation
Hyper metal poor (HMP) stars
Cut-off of MDF
Assumptions
Results -6 -5 -4 -3 -2
MDM~106M☉
Mgas~105M☉
[Fe/H]=-4~-2.5 mstar~10M☉
銀河形成
現在: Population I
最初は小さなガス雲の中で星形成が起きる
Population III形成
Population II 形成 Mgas~1011M☉
disk 形成。
EMP 形成
2 段階に分けて考える
合体
Hierarchical galaxy formationHierarchical galaxy formation
• The cut-off is originate from structure formation process
46
0.0710
10Fe
solarcloud baryon
MZ Z
M
1st mini-halo ~ 106-7 M☉
SN
[Fe/H]~-4
After 1st SN explosion,
Pop.3 stars still alive HMP star. ⇒(Suda et al.2004)
MDF cut-off at [Fe/H]~-4
2nd star [Fe/H]~-4
merge
Merger tree
z
mini-haloの質量(M☉)
0.1 0.2 0.5 1 ( Big Bang からの時間 Gyr)
(実際は枝の数はこの 1000倍)
このようなtree での化学進化を計算
Effect of structure formationEffect of structure formation
Merging history: Press-Schechter(Somerville & Kollat1999)
Model predict cut-off at [Fe/H]~-4.
SFE: 10-10/yr
Observed MDF
Theoretical MDF with merger tree.
Number of stars with Z = 0 is inconsistent.
Results
Assumptions
First starFirst star
Mmd =100 M☉ for Z=0. Pair-Instability supernovae (Fe yield: 10M☉)
⇒iron overproduction
First star : supermassive not PISN.
初代星への表面汚染• Mini-halo の中では恒星の運動速度が遅いために、
星間ガスの恒星表面への降着が起きやすい
金属 0 で誕生
周囲の星間物質を降着[Fe/H]~-3
連星の場合は主星からの質量降着(炭素星に) [Fe/H]<-5
赤色巨星に[Fe/H]<-5
汚染を考慮した MDF
3.3.3 Database of Galactic EMP Stars for Galactic Archaeology
ContentsContents• Papers: Papers: 9696 (covering since 2000) (covering since 2000) on high resolution spectroscopy
• Stars: Stars: 1495(847)1495(847)• DataData
– [X/Fe]: [X/Fe]: 24,49824,498– [X/H]: [X/H]: 26,09026,090– loglogεε: : 26,09026,090– LL ogog g, etc; atmospheric data, g, etc; atmospheric data,
[Fe/H] Number(prev.)[Fe/H] Number(prev.)
-1< -1< 124124 -1~-2 -1~-2 214214 -2~-3 -2~-3 419419 -3~-4 -3~-4 117117 <-4 <-4 44
[Fe/H] Number(prev.)[Fe/H] Number(prev.)
-1< -1< 124124 -1~-2 -1~-2 214214 -2~-3 -2~-3 419419 -3~-4 -3~-4 117117 <-4 <-4 44
(DaGaAr: Suda et al. 2007)
Sample characteristics
Magnitude distributionamong samplesselection effects due to survey
Teff - surface
gravity
dwarfs
giants
Metallicity distribution
[Eu/
Fe]
[Fe/H]
Eu: neutron capture element
r-process + s-process
r-process only[Eu/Ba] > 0
Space distributions of EMP stars
Distance ← surface gravity (assuming M=0.8 M)
dwarfs
giants
Astrometry +Spectroscopy (e.g., WFMOS ) ↓位置、運動、光度、組成 ⇒ 年齢
銀河の恒星地図銀河形成史の再構築