初代星初代銀河研究会2015 @ 東北大学 2015/01/19 15mm 元素合成と恒星進化モデルで探る 極超金属欠乏星の起源 須田 拓馬（東大RESCEU） 共同研究者 小宮 悠 (東大RESCEU), 山田 志真子 (北大), 藤本 正行 (北海学園大) とができなくなります。 この最小使用サイズは い。また、印刷方式、媒体の条件などによって Chemical Evolution of the Universe Molecular Clouds Metal-Deficient Stars (Metal-Poor Stars) = Ancient Stars Proto Stars Main Sequence Stars 恒星進化・元素合成 化学進化 星形成 銀河形成 Supernova Remnant Supernovae Red Giant Stars Planetary Nebulae White Dwarfs History of Search for Pop. III [Fe/H] 1948:Gamov Big Bang 0 -1 -2 primordial nucleosynthesis HD 140283: [Ca/H]=-1.9 [Fe/H]=-1.2 (-2.5) Bond survey [Fe/H] -2.6 Bond70,80 Chamberlian+Aller51 HK survey (1985:1992) no stars below [Fe/H]<-3 HE survey (1990:2001) Bond81 -3 HE 0557-4840 [Fe/H]=-4.75 G 64-12 [Fe/H]=-3.5(-3.28) -4 Norris+07 Carney+Peterson81 HE 0107-5240 [Fe/H]=-5.3 CD -38 245 [Fe/H]=-4.5(-4.01) -5 Initial measurement -7 1950 1960 G 77-61 [Fe/H]=-5.6 (-4.03) Gass+87 corrected value 1970 1980 SDSS J102915+172927 [Fe/H]=-4.99 Caffau+11 Christlieb+02 Bessel+Norris84 -6 SEGUE, Skymapper ( 2010-) HE 1327-2326 [Fe/H]=-5.6 SMSS J0313-6708 [Fe/H]<-7 Keller+14 Frebel+05 1990 2000 2010 2020 Carbon-Enhanced Metal-Poor (CEMP) Stars and Hyper/Ultra Metal-Poor Stars • • HMP stars as the candidates of the first stars related to low-mass star ( 0.8M ) formation • What is the minimum metallicity to form low-mass stars? CEMP stars are common among Extremely Metal-Poor (EMP) stars (CEMP/EMP 0.2). • 1 0 Li C O -1 [X/H] -2 -3 HE0107-5240 CNO-rich: HE1327-2326 (1D LTE) HE1327-2326 (3D correction) Origin of CEMP Iron group: HE0557-4840 Supernova models SDSS J102915+172927 SMSS J0313-6708 Pollution & accretion Na Al S Ca Ti Cr Fe Ni Zn Sr -4 -5 -6 -7 -8 N 5 Mg Si 10 15 Sc 20 Mn Co 25 Neutron-capture elements: Origin of CEMP-s/no 30 35 40 Atomic Number (Z) Ba 45 50 55 60 Eu 65 SAGA viewer • • Proposed Scenarios for the Origins of CEMP Stars Origin of EMP stars • Binary Scenario Star formation from the gas influenced by SNe in the very early universe. Origin of CEMP stars • • • Mass transfer from AGB stars in binary systems (TS+04) • CEMP-s stars are thought to belong to binary systems (Lucatello+05), but not for CEMP-no. Star formation from gas affected by peculiar supernovae in the earliest generation of massive stars (Umeda+03, Limongi+04) • Abundance patterns are well reproduced by mixing and fallback models. Star formation affected by massive fast-rotating stars (Meynet +06) • Abundance patterns are well reproduced by rotational mixing. TS+04 Spinstar Scenario Faint-SN Scenario Meynet+06 Umeda+Nomoto03 Binary Scenario for the Origin of CEMP Stars TS+Fujimoto10, see also Fujimoto+00 -1 CHCase stars IV (Population I, II) -2 -3 [Fe/H] He-FDDM Case II -4 0.1 -5 10-2 10 -5 10-8 0.1 0 10-2 CEMP-s 10-3 10-6 10-5 10-7 0 Case IV’ CEMP-no C burning Case II’ It is expected that the typical mass of stars are more massive than that expected Case IIIfrom the Case I present day IMF (Komiya+07, Lucatello+06). Z=0 0.8 1.0 1.2 Population III 1.5 2.0 Ritossa+99 Gil-Pons+Doherty10 2.5 3.0 4.0 5.0 6.0 7.0 8.0 9.0 Mini He-Flash Driven Deep Mixing: H-ingestion into the He-flash convective zone Fujimoto+90, Hollowell+90, Cassisi+96, Fujimoto+00, Schlattl+02, Suda+04, Iwamoto +04, Picardi+04, Herwig+05, Campbell+Lattanzio+08, Lau+09, Cristallo+09, Iwamoto09, Campbell+09, Suda+Fujimoto10, Cruz+13 Stellar Evolution & Binary Evolution C, N, s-elements Roche Lobe overflow or Wind accretion? -> depends on separation and mass ratio. The fraction of CEMP (or NEMP) stars can be estimated by assuming Initial mass function distribution function of binary mass ratio distribution function of binary period Binary Population Models and Comparisons with Observed CEMP Fractions Fraction of C-rich stars 炭素過剰星の割合 1.0 [C/Fe]>0.7 Observations 0.6 High-mass IMF 0.2 Salpeter IMF -4 Fraction of C-rich stars IMF transition 0.4 1.0 炭素過剰星の割合 SAGA Database SEGUE (Lee+2013, Outer halo) High-Mass IMF Salpeter IMF 0.8 0.0 Aoki+07 TS+11 Giants Dwarfs 0.8 -3 -2 -1 [Fe/H] SAGA Database SEGUE (Lee+13) High-Mass IMF Salpeter IMF statistical uncertainty? sampling effect? Observations 0.6 High-mass IMF 0.4 0.2 TS+13 Lee, TS+14 Salpeter IMF 0.0 -4 -3 -2 [Fe/H] -1 CNO, 軽元素, 中性子捕獲元素の起源 Hydrogen Ingestion Into the He-Flash Convective Zone 0.640 2M , [Fe/H]=-4 4 0.635 0.625 M1 0.620 Mbhs 0.615 Proton Ingestion 2 1 [N/Fe] 0.610 0 [C/Fe] 0.605 0.600 3 [X/Fe] Mr(Msun) 0.630 MCO 20 40 60 80 100 110 TS+Fujimoto10 112 114 116 Time (year) 118 120 500 1000 -1 Campbell+Lattanzio08 Proton Ingestion He対流層への水素の混入。水素層との entropy barrierが少ないために起こ る。水素flashを伴い、その後の表面対 流層の侵入によってCNが増大。 1.5M [Fe/H]=-3.3 Lau+09 CNO, 軽元素, 中性子捕獲元素の起源 Nucleosynthesis models • One zone approximation during the He shell flashes (Fujimoto+99, • p-, α-, β-, n-reactions up to Aikawa+01) log THe,conv He flash対流層の底の温度 are included in nuclear network (Aikawa+01, Nishimura+08, Yamada+, in prep.). Proton Ingestion Initial Z=0 1.5-7 M AGB phase 8.6 84Po model 1 model 2 model 3 model 4 8.5 8.4 8.3 3 4 5 6 7 8 9 10 11 12 log t (sec) after the appearance of He-convection CNO, 軽元素, 中性子捕獲元素の起源 Comparisons of Models with Observations Case: HE 0107-5240 0 -1 -2 [X/H] -3 -4 log(Tmax) = 8.52 (model 3) 8.45 (model 4) HE0107-5240(Christlieb+02) 12 dtmix=1e+8, 13 C/ C=0.002 (Model 3) 13 12 dtmix=1e+8, C/ C=0.002 (Model 4) C-abundanceで規格化 Na Mg Al Sr Ba -5 -6 -7 -8 5 6 7 8 9 10 11 12 13 14 15 16 17 20 25 30 35 40 45 50 55 60 65 70 75 80 Atomic Number (Z) see also 少量の水素混合 He-FDDMによるNa, Mg, Alの生成(TS+04) low- or intermediate-mass AGB stars TS+04 CNO, 軽元素, 中性子捕獲元素の起源 Comparisons of Models with Observations Case: HE 1327-2326 0 HE1327-2326(1D,Aoki+06) HE1327-2326(3D,Frebel+08) 12 dtmix=1e+7, 13 C/ C=0.03 (Model 3) 13 12 dtmix=5e+6, 13C/12C=0.03 (Model 3) dtmix=5e+8, C/ C=0.02 (Model 2) -1 -2 Na [X/H] -3 -4 Mg Al Sr Ba -5 -6 -7 -8 5 6 7 8 9 10 11 12 13 14 15 16 17 20 25 30 35 40 45 50 55 60 65 70 75 80 Atomic Number (Z) 大量の水素混合 He-FDDMによるNa, Mg, Alの生成、Sr/Ba大 low-mass AGB stars CNO, 軽元素, 中性子捕獲元素の起源 Comparisons of Models with Observations Case: SMSS J0313-6708 -2 -3 Na SMSS J0313-6708 (Keller+14) dtmix=1e+6 (Model 1) dtmix=1e+6 (Model 2) Mg -4 [X/H] -5 Al -6 Sr Ba -7 -8 -9 -10 5 6 7 8 9 10 11 12 13 14 15 16 17 20 25 30 35 40 45 50 55 60 65 70 75 80 Atomic Number (Z) 22Ne(α,n)25Mg起源のs-process high-mass AGB stars (core mass大 or log T > 8.5) 22Neを効率よく燃やさない限り23Naがoverproduction 鉄属元素の起源 Hierarchical clustering scenario chemical evolution pre-enrichment of IGM First stars Mini-halo 106M First supernova surface pollution in ISM Proto-galaxy Milky Way IGM: inter-galactic medium, SN ejecta can pollute other mini-halos ISM: inter-stellar medium, SN ejecta can pollute other stars within the mini-halo 鉄属元素の起源 Pollution and Accretion SN ejecta pollute the IGM and potentially pollute other mini-halos. SN ejecta pollute the ISM and the stellar envelopes with metals. Ingredients for galaxy/star formation/evolution Extended Press-Schechter theory High-mass IMF w. const. SF rate 2 log (m1 /10M ) (log m1 ) exp 2 0.42 Binary evolution mass ratio function period distribution mass transfer Chemical evolution semi-closed boxes in each mini-halo Accretion of SN ejecta Bondi-Hoyle accretion Accretion onto binaries IGM pollution/accretion outflow from proto-galaxies evolution of the Galactic wind pre-enrichment of proto-galaxies 鉄属元素の起源 With accretion Pollutionを考慮しないと Pop.IIIが多くなりすぎる！ No accretion Polluted EMP Polluted Pop.III 第二世代は [Fe/H]<-5がほと んど存在しない。 stellar column density number of stars covered by HES Surface pollution by interstellar medium Komiya+in prep. 鉄属元素の起源 Pre-enrichment of host halo due to pollution by external SN ejecta 外部のFirst SNによって星表面へ の降着を受けた第一世代星。 外部のFirst SNによって汚染され たpre-enrichmentを受けたminihaloの第一世代星。 1st and 1st gen. 2nd gen. ISM pollution IGM pollution Komiya+in prep. Open Questions: CEMP-no/CEMP-s ratio (1)[Fe/H] < -3.5でCEMP-noが支配的 • CEMP-s が [Fe/H] < -3.5で消滅!? • CEMP-no は[Fe/H] = -3.5から増加 • CEMP-s + CEMP-noは連続 s-processが[Fe/H] 依存性を持ってい ると考えるのが妥当 (2)[Fe/H]<-3.5でCの増大量が異なる • [C/H] 0 at [Fe/H] > -3. • [C/H] < -1 at [Fe/H] < -3.5. • TDUの効率が減少 • [Fe/H] < -4でflashが弱くなる(TS+10) [C/Fe] and [C/H]➡ with [Fe/H]➡ 2.0 CEMP-s 862 の 率 効 p u ge 0.0 ed r d -1.0 binarity unlikely for CEMP-no ? 少 減 C-normal CEMP CEMP-s CEMP-no 1.0 [C/H] Fraction 28+-9% below [Fe/H]=-3.1 -2.0 -3.0 4/5 for UMP/HMP CEMP-no -4.0 -5.0 -5 -4 [Fe/H] fit: [C/H]=0.876[Fe/H]-0.175 -3 -6.0 -6.0 Norris+13 -5.0 -4.0 -3.0 [Fe/H] -2.0 -1.0 0.0 TS+11 s-process efficiency dependent on metallicity? 2.0 1.0 CEMP,RGB CEMP,MS CEMP-s,RGB CEMP-s,MS CEMP-no,RGB CEMP-no,MS [Ba/C] 0.0 171 CEMP: [C/Fe] > 0.7 CEMP-s/no: [Ba/Fe] = 0.5 s-processの 金属量依存性 -1.0 -2.0 r-processの寄与 Komiya,TS+14 -3.0 -4.0 -6.0 -5.5 -5.0 -4.5 -4.0 -3.5 [Fe/H] -3.0 -2.5 -2.0 -1.5 -1.0 SAGA: ver. 2015-01-07 まとめと議論 超金属欠乏(EMP)星([Fe/H] < -2.5)の特徴 炭素過剰星(CEMP)星の割合が大きい。 CEMP星はCEMP-s (s-processの増大あり)とCEMP-no (s-process増大なし)に分類される。 EMPに対するCEMP-s / -no割合に[Fe/H]依存性が見られる。 連星として確認された割合が異なり、CEMP-sはAGBからの質量輸送で説明可能。 なぜ金属欠乏星には炭素過剰(CEMP)星が多いのか？ 炭素過剰星の割合はAGB星からの質量輸送とhigh-mass IMFで説明可能。 炭素過剰星割合の変化から、初期質量関数は[Fe/H]~-2の時代に変遷があった可能性がある。 いわゆるHyper Metal-Poor Stars ([Fe/H] < -5)はAGB星からの質量輸送の影響を受け、かつ星間 空間で汚染を受けた星である可能性が高い。 特異な元素組成パターンの再現。 極端に少ない鉄属元素量の実現。 なぜCEMP-no/CEMP比は[Fe/H] < -3.5で大きくなるのか？ 通常のモデルでは、intermediate-mass AGBでCEMP-noが作られると仮定すると(Suda et al. 2004, 2010)、CEMP-no/CEMP~0.2 (High-mass IMF) となり、観測値を説明するのは困難。 Low-mass IMFでは、CEMP-no/CEMP<0.02とさらに少ない。 EMP AGB星におけるs-processが金属量依存性を持つ可能性がある。 EMP星では短周期連星が作られやすい？(Aoki, TS+15) metal-poor stars (not EMP)では1000日以下の連星が最も多い(Rastegaev10)
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