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野沢 貴也 （ Takaya Nozawa ） 国立天文台 （ NAOJ ）　 理論研究部

2015/04/15. 高赤方偏移クェーサー母銀河中の 星間ダスト進化と減光曲線 (Evolution of grain size distribution in high-redshift dusty quasars: integrating large amounts of dust and unusual extinction curves). 野沢 貴也 （ Takaya Nozawa ） 国立天文台 （ NAOJ ）　 理論研究部. 共同研究者 浅野 良輔、竹内 努 ( 名古屋大学 ) 、平下 博之 (ASIAA). References

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野沢 貴也 （ Takaya Nozawa ） 国立天文台 （ NAOJ ）　 理論研究部

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  1. 2015/04/15 高赤方偏移クェーサー母銀河中の星間ダスト進化と減光曲線(Evolution of grain size distribution in high-redshift dusty quasars: integrating large amounts of dust and unusual extinction curves) 野沢 貴也 （Takaya Nozawa） 国立天文台 （NAOJ）　理論研究部 共同研究者 浅野 良輔、竹内 努 (名古屋大学)、平下 博之 (ASIAA) References ・ Asano, Takeuchi, Hirashita, Nozawa (2013, MNRAS, 432, 637) ・ Asano, Takeuchi, Hirashita, Nozawa (2014, MNRAS, 440, 134) ・ Nozawa, Asano, Hirashita, Takeuchi (2015, MNRAS, 447, L15)

  2. 1-1. A large amount of dust in high-z quasars ○ Discovery of massive dust in excess of 108 Msun in quasar hosts at z > 5 (Bertoldi+2003, Priddey+2003, Robson+2004, Beelen+2006) e.g.,SDSS J1148+5251 at z=6.4 - cosmic age : 890 Myr - stellar mass : ~1011 Msun -SFR : ~3000 Msun/yr (Salpeter IMF) -gas mass : >~3x1010 Msun -IR luminosity : (1-3)x1013 Lsun -dust mass : (2-7)x108 Msun - dust-to-gas mass ratio : ~0.01 Bertoldi+2003 dust emission stellar emission ○ Sources of dust in the early universe ➜ core-collapse supernovae (CCSNe) ‐dust evolution model : >0.1-1 Msun per SN (Morgan & Edmunds 2003; Maiolino+2006; Dwek+2007) ‐theoretical studies of dust formation :~0.1-1.0 Msun per SN (Todini & Ferrara 2001; Nozawa+2003, 2007; Bianchi & Schneider 2007) Leipski+2010

  3. 1-2. Extinction curves in high-z quasars SDSS J1048+4637 at z=6.2 : broad absorption line (BAL) quasars UV extinction curve Maiolino+2004, Nature, 431, 533 The interstellar dust in the epoch as early as z=5 was predominantly supplied by CCSNe?

  4. 1-3. What are dust sources in quasars at z > 5? Dust mass (Msun) Dust-to-gas mass ratio Gas mass (Msun) Gas mass (Msun) Calura+2014 ○AGB stars+ SNe ‐AGB stars contribute more dust grains than CCSNe (Valiante+2009; Dwek & Cherchneff 2011) ‐dust formation calculation: 0.01-0.05 Msun per AGB star (Zhukovska & Gail 2008) ○ Grain growth in molecular clouds+ AGB stars +SNe (Draine 2009; Michalowski+2010; Gall+2011a, 11b; Pipino+2011; Mattsson+2011; Valiante+2011; Inoue 2011; Kuo & Hirshita 2012; Calura+2014; Michalowski 2015) Dwek & Cherchneff(2011)

  5. 1-4. Inconsistency in the origin of high-z dust unusual extinction curve huge amounts of dust grains Can we explain self-consistently the massive dust and unusual extinction curve observed for high-z quasars? ??? SN dust only ! SN dust + AGB dust anddust growth

  6. 1-5. Life-cycle of interstellar dust ビッグバン 分子雲中での ダストの成長 星間空間中での ダストの破壊・変性 星間空間 原始惑星系円盤 分子雲 惑星系の形成 星の誕生 星間空間への ダスト供給 大質量星 超新星爆発 質量放出 中小質量星 ダストは様々な天体現象と密接に関わっており、銀河中のダストの サイズ分布・存在量は星形成活動とともに時々刻々と変化する

  7. 1-6. Aim of our study In the past dust evolution models, the size distribution of dust is assumed to be - a single size (e.g., a=0.01 µm or 0.1 µm) or - that in our Galaxy, with no time evolution Recently, we constructed, for the first time, the evolution model of dust size distribution, which considers the following dust processes: - production of dust in CCSNe and AGB stars - destruction of dust by interstellar shocks - grain growth due to metal accretion in molecular clouds -shattering and coagulation due to grain-grain collisions (Asano, Takeuchi, Hirashita, TN 2013) We apply this dust evolution model to study the evolution of dust size distribution and the extinction curves in high-z dusty quasars Gall+2011a

  8. 2-1. Formation/destruction processes of dust Dust ejected from CCSNe Dust ejected from AGB stars coagulation Yasuda & Kozasa 2012 Nozawa+2007 shattering grain growth: accretion of gas-phase heavy elements onto pre-existing dust Sirono+2013 Hirashita & Yan+2009

  9. 2-2. Dust evolution model in a galaxy (1) ‐one-zone closed-box model (no inflow and no outflow) ‐SFR(t) = Mgas(t)/τSF(Schmidt law with n = 1) ‐Salpeter IMF: φ(m) = m-qwith q=2.35 for Mstar = 0.1-100 Msun ‐dust processes - production of dust in SNe II and AGB stars - destruction of dust by interstellar shocks - grain growth due to metal accretion in molecular clouds -shattering and coagulation due to grain-grain collisions ‐two dust species: - graphite (carbonaceous grains) - silicate (grains species other than carbonaceous grains) ‐multi-phase ISM - WNM (warm neutral medium): T = 6000 K, n = 0.3 cm-3 - CNM (cold neutral medium): T = 100 K, n = 30 cm-3

  10. 2-3. Dust evolution model in a galaxy (2) xSFR(t), astration ‐evolution of dust mass ΔMd(a,t)with radii between a and a+da dust production by SNe II and AGB stars shock destruction grain growth shattering coagulation

  11. 2-4. Evolution of extinction curvesin galaxies grain size distribution dust amount extinction curve MRN τSF=5 Gyr WNM=0.5 CNM=0.5 Asano, Takeuchi, Hirashita, TN+2013, 2014 ‐early phase:formation of dust in SNe II and AGB stars 　➔ large grains (>0.1 μm） are dominant➔ flat extinction curve ‐middle phase: shattering, grain growth due to accretion of gas metal ➔ small grains (< 0.03 μm） are produced➔ steep extinction curve ‐late phase: coagulation of small grains ➔ shift of peak of size distribution ➔ making extinction curve flatter Asano+12

  12. 2-5. Life-cycle of interstellar dust ビッグバン 分子雲中での ダストの成長 星間空間中での ダストの破壊・変性 星間空間 小さいダスト の支配的成長 原始惑星系円盤 乱流中の衝突破砕に よる小さいダストの生成 分子雲 惑星系の形成 星の誕生 星間空間への ダスト供給 大質量星 超新星爆発 比較的大きいダストの供給 質量放出 中小質量星 ダストは様々な天体現象と密接に関わっており、銀河中のダストの サイズ分布・存在量は星形成活動とともに時々刻々と変化する

  13. 3-1. Reproducing the MW extinction curve ‐two-phase ISM ・ WNM (T = 6000 K, n = 0.3 cm-3) ・ CNM (T = 100 K, n = 30 cm-3) WNM=0.5 CNM=0.3 MC=0.2 ‐three-phase ISM ・ WNM (T = 6000 K, n = 0.3 cm-3) ・ CNM (T = 100 K, n = 30 cm-3) ・ MC (molecular clouds) ➜ T = 25 K, n = 300 cm-3 Nozawa+2015 - three-phase ISM model including the MC phase can reproduce the average extinction curve in the MW - ISM phase is one of the important quantities in constructing the evolution model of interstellar dust

  14. 3-2. Explaining massive dust in high-z quasars high-z quasar host: starburst galaxies ➜ indicating a high fraction of MC MH2/MH,total ~ 0.7-0.97 (Calura+2014) ‐two-phase ISM: WNM=0.3 and MC=0.7 ‐τSF = 0.5 Gyr Grain growth is necessary to achieve the observed high D/G Nozawa+2015

  15. 3-3. Explaining the high-z extinction curves The presence/absence of 2175 A bump may be related to the dust composition of dust rather than the dust evolution model - graphite and silicate - amorphous carbon & silicate ➜ the derived extinction curve well match the observed high- z extinction curve Nozawa+2015 The origin of the 2175 A bump is still unclear ➜ small size (<0.02 µm) of graphite? (e.g., Draine & Lee 1984) ➜ PAHs (polycyclic aromatic hydrocarbon?) (e.g., Joblin+1992) ・ formation site of PAHs - AGB stars? (bottom-up scenario) (e.g., Cherchneff+1993) - shattering of C grains? (up-down scenario) (e.g., Seok+2014)

  16. 4. Summary We investigate the evolutions of grain size distribution and the extinction curves in high-z dusty galaxies ・ our dust evolution model can reproduce the average extinction curve in the MW by considering - three-phase ISM (WNM=0.5, CNM ~ MC ~ 0.25) - graphite & silicate ・ a large amount of dust grains and the unusual extinction curve observed for high-z quasars can be explained by considering - a large mass fraction of MC (>0.5) in the ISM ➜ efficient growth/coagulation of dust grains - amorphous carbon & silicate ➜ different properties of carbonaceous dust ## It is possible that the quasar extinction curves reflect the properties ## of dust in circumnuclear (AGN) torus, not those of interstellar dust

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