野沢貴也（ Takaya Nozawa ）国立天文台理論研究部 (Division of theoretical astronomy, NAOJ)

2018/10/15 超新星ダスト形成の課題と超新星でのSiC粒子の形成(Issues of dust formation in supernovae and Formation of SiC grains in supernovae) 野沢貴也（Takaya Nozawa）国立天文台理論研究部 (Division of theoretical astronomy, NAOJ) Special thanks: Masaomi Tanaka (Tohoku Univ.), Hidekazu Tanaka, Kyoko K. Tanaka (Tohoku Univ.), Takashi Yoshida, Hideyuki Umeda (Univ. of Tokyo), Yuki Kimura (Hokkaido Univ.),Shigeru Wakita (ELSI)

1-1. Discovery of massive dust at z > 5 The far-infrared and submm observations have confirmed the presence of dust in excess of 108 Msun in 30% of z > 5 quasars 108-109 Msun of dust in SDSS J1148+ 5251 at z=6.4 Leipski+2010 ~106 Msun of dust in a galaxy at z = 8.4 Laporte+2017 ‐In the MW, AGB stars are considered to be major dust sources➜ too old to supply dust in the early universe ‐0.1 Msun of dust per SN is needed to explain massive dust at high-z (e.g. Morgan & Edmunds 2003; Maiolino+2006; Dwek+2007)

1-2. Key questions for dust formation in SNe 1. How much dust grains form? 2. What is the size distribution of dust? 3. When do the majority of grains form?

1-3. Emission/absorption efficiency of dust ○ Thermal radiation from dust grains Fλ = Ndust 4πa2Qemis(a,λ) πBλ(Tdust) #Qemis = Qabs carbon silicate (Qemis/a) is independent of a Fλ = Ndust 4πa3(Qemis[a,λ]/a) πBλ(Tdust) = 4 Mdust κabs(λ) πBλ(Tdust) ➔ IR emission is derived given Mdust, κabs, and Tdust

2-1. Observed dust mass in CC-SNe/SNRs reverse shock destruction ?? ?? NIR/MIR FIR/submm extinction Matsuura+2011 Gomez+2012 Balow+2010 Dust mass formed in the ejecta is dominated by cold dust

2-2. Formation and processing of dust in SNe Nozawa 2014, Astronomical Herald Destruction efficiency of dust grains by sputtering in the reverse shocks depends on their initial size The size of newly formed dust is determined by physical condition (gas density and temperature) of SN ejecta

2-3. ALMA reveals dust formed in SN 1987A SED of 25-years old SN 1987A ALMA, 1.4 mm ALMA, 870 µm ALMA, 450 µm HST optical (HI) Chandra, X-ray Indebetouw+2014 ALMA spatially resolves cool (~20K) dust of ~0.5 Msun formed in the ejecta of SN 1987A ➔ SNe could be production factories of dust grains

2-4. Properties of dust ejected from SNe II-P Nozawa+07, ApJ, 666, 955 SNe II total mass of dust surviving the destruction in Type II SNRs; 0.07-0.8 Msun(nH,0 = 0.1-1 cm-3) size distribution of dust after the shock-destruction is domimated by large grains (> 0.1 μm)

2-5. Survival of dust within an old SNR Sagittarius A East SNR ・ age: ~10,000 yr ・ dust mass: ~0.02Msun ・ dust temperature: ~100 K Lau+2015, Science

3-1. Observed dust mass in CC-SNe/SNRs reverse shock destruction ?? missing cold dust? Dust mass increasing with time? ?? NIR/MIR FIR/submm extinction Dust mass formed in the ejecta is dominated by cold dust

3-2. Dust mass increases with time? Dust mass estimated from IR SEDs Gall et al. (2014, Nature) Most of dust grains (> 0.1 Msun) form at ~20 yr post-explosion Evolution of dust mass in SN 1987A derived from extinction of optical emission lines Bevan & Barlow (2016)

3-2-1. Dust mass from line profiles in SN 1987A OI 6300 Bevan & Barlow 2016 At 714 day ・ dust mass < 3x10-3 Msun (< 0.07 Msun if silicate) ・ grain radius > ~0.6 µm

3-3. Interpretation of Gall et al. (2014) paper Dust formed in the ejecta Gall+2014, Nature Dust formed in cool dense shell Pre-existing circumstellar dust The mass of newly formed dust increases with time? We should not discuss the mass of newly formed grains by integrating the formation of dust in the ejecta and CDS

3-4. Timescale of grain growth At 20 yr, the gas density is too low to form dust grains in the freely expanding ejecta

4-1. Key questions for dust formation 1. How much dust grains form? ‐theoretical works ➜0.1-1 Msun ‐FIR/submm obs. ➜0.1-1 Msun 2. What is the size distribution of dust? ‐theory ➜ relatively large grains (>0.1 µm) in SNe II ‐obs.➜ large (~0.1-1 µm) at the dust formation 3. When do the majority of grains form? ‐theory ➜~1-3 yr (within 5 yr; earlier is better) ‐obs. ➜ ~20 yr (dust mass gradually increases with time)

4-2. Observed dust mass in CC-SNe/SNRs reverse shock destruction ?? missing cold dust? Dust mass increasing with time? ?? NIR/MIR FIR/submm extinction Dust mass formed in the ejecta is dominated by cold dust

4-3. 3-D structure of Cas A SNR Orlando+2016 Milisavljevic+2013 Calculations of dust formation and destruction in 3-D simulations of SNe/SNRs would be highly useful.

4-4. 3D-structure of CO and SiO emission Abellan+2017

4-5. Formation condition of presolar Al2O3 presolar Al2O3 grains Al2O3 (Nittler+1997) Nozawa+2015, ApJ, 811, L39 Submicron-sized presolar Al2O3 grains identified as SN-origin were formed in dense clumps in the ejecta

4-6. How we tackle unsolved problems? 2. What is the size distribution of dust? ‐would not easy to constrain grain sizes from optical/NIR extinction ➜ Calculations of dust formation/destruction in 3-D SN simulations are critical to predict grain sizes ➜ SN-origin presolar grains are useful tools to probe the condition of SN ejecta 3. When do the majority of grains form? ‐JWST will not do a good job to answer this question ➜ SPICA will be able to resolve this problem ➜ We just expect that a supernova explosion occurs in MW/LMC/SMC in near future

1-1. Presolar grains ○ Presolar grains ‐ discovered in primitive meteorites and IDPs ‐ showing peculiar isotopic compositions (different from the solar system’s materials) ‐ thought to have formed in stars before the Sun was formed ➜ offering key information on ・ nuclear processes in the parent stars ・ physical conditions in which they formed ‐ abundance (volume fraction): ~100-500 ppm (~0.01-0.05 %) ‐ mineral composition graphite, SiC, TiC, Si3N4, Al2O3, MgAl2O4, Mg2SiO4, MgSiO3 … http://presolargrains.net/

1-2. Presolar Type X SiC grains Nittler 2003 ○ PresolarSiC grains (~10 ppm) Nittler & Hoppe 2005 〇 Type X SiC grains (~0.1 ppm, size: 0.1-20 µm) ‐ 12C and 28Si rich, with excesses in 44Ca (44Ti), 49Ti (49V) ➜ originated from core-collapse supernovae

1-3. Long-lasting questions 〇 Fact A fraction of presolar SiC grains is highly likely SN-origin 〇 Question How do these SiC grains form in the ejecta of core-collapse supernovae? ## Any theoretical studies have not yet realized the ## formation of SiC grains in supernovae

2-1. Where SiC grains form in the ejecta? Si isotopes 44Ti 28Si rich 12C rich C (N) isotopes Yoshida 2007; 4 Msun He-core model (Mstar ~ 18 Msun) O-rich (O/C >> 1) 29, 30Si rich 29, 30Si solar 14N rich require special condition of ejecta mixing

2-2. Possible formation site of SiC grains in SNe 16O 4He 12C ○ Moderately energetic SNe Ekin = (3-5)x1051 erg (normal SNe : Ekin ~ 1x1051 erg) explosive burning happens at the boundary between O-rich region and He-rich region ➜ producing 12C-rich, 28Si-rich, (44Ti-rich) region ## 3(4He)  12C ## 12C + n(4He) ➜ α-elements 28Si Pignatari+2013 Umeda & Nomoto 2002

2-3. No formation of SiC in the calculations 〇 Condensation temperature ‐C grains : Tcon = 1700-2200 K ‐SiC grains: Tcon = 1300-1800 K ➜ In C/Si-rich gas, C grains first condense to use up the gas- phase C atoms 〇 Formation path of grains cool down More efficient destruction of C grains (clusters)? UV radiation, high-energy e, chemical reaction, … ➜ this may not do a good job

2-4. Formation of SiC grains via molecules 〇 Previous works ➜ accretion of Si/C atoms 〇 This work ‐accretion of SiC molecules ‐coagulation rate coefficients of radiative association of molecules ki,j Andreazza+2009

3-1. Formation of SiC molecules Pignatari+2013

3-2. Equation of dust formation 〇 Master equations of dust growth taking account of nucleation and grain growth through gas accretion and coagulation between grains simultaneously!

3-3. Can SiC grains form in the SN ejecta? behavior of dust formation size distribution of dust Yes,the formation of SiC grains is possible !

3-4. Size distribution of SiC grains formed ‐ Radius of newly formed grains is larger for higher gas density ‐ For the gas densities considered in this study, grain radii cannot reach ones (> 0.1 µm) observed in presolar SiC grains

3-5. Dependence of grain radius on density Average radius of dust grains Mass fraction of dust grains ‐ Radius of newly formed grains is larger for shorter τ_cool ‐ Radius and mass of SiC grains are lower than those of C grains by factors of ~5 and ~10, respectively.

4-1. Formation process of SiC grains 〇 Formation of SiC grains is possible !! ‐ Condensation temperature is higher for higher gas density ‐ Dust growth proceeds on a short timescale through rapid accretion of molecules ‐ Coagulation makes the average radius by about a factor of 2

4-2. Effect of grain-grain coagulation Size distribution of dust grains Average radius of dust grains ‐ Radius of newly formed grains is larger for shorter τ_cool ‐ Radius and mass of SiC grains are lower than those of C grains by factors of ~5 and ~10, respectively.

5. Summary of the latter part of this talk We investigate the formation of SiC grains in the ejecta of supernovae, self-consistently treating ‐formation of SiC molecules ‐growth of SiC grains via accretion of molecules ‐growth of SiC grains via grain-grain coagulation We have realized, for the first time, the formation of SiC grains in the ejecta of supernovae but… formation of large presolar Type-X SiC grains above 0.1 µm is still difficult ➜ >30 times higher gas density ➜ efficient dust growth by grain-grain coagulation

野沢貴也（ Takaya Nozawa ）国立天文台理論研究部 (Division of theoretical astronomy, NAOJ)