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 andFormation 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 thepresence of dust in excess of 108 Msun in 30% of z > 5 quasars
108-109 Msunof dust inSDSS J1148+
5251 at z=6.4
Leipski+2010~106 Msun ofdust 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 4πa2 Qemis(a,λ) πBλ(Tdust) # Qemis = Qabs
carbonsilicate(Qemis/a) is independent of aFλ = 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
Matsuura+2011
FIR/submm
Balow+2010
extinctionGomez+2012

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 thereverse shocks depends on their initial size

The size of newly formed dust is determined by physicalcondition (gas density and temperature) of SN ejecta

2-3. ALMA reveals dust formed in SN 1987A
ALMA, 1.4 mm

ALMA, 870 µm

ALMA, 450 µm

HST optical (HI)Chandra, X-ray

SED of 25-years old SN 1987A

Indebetouw+2014

ALMA spatially resolves cool(~20K) dust of ~0.5 M sun formedin 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 thedestruction in Type II SNRs;
0.07-0.8 Msun (nH,0 = 0.1-1 cm-3)

size distribution of dust after theshock-destruction is domimatedby large grains (> 0.1 μm)

2-5. Survival of dust within an old SNR
Sagittarius A East SNR・ age: ~10,000 yr

・ dust mass: ~0.02 Msun・ dust temperature: ~100 K
Lau+2015, Science3-1. Observed dust mass in CC-SNe/SNRs
reverse shock
destruction??
missing
cold dust?

Dust mass
increasingwith time?

??

NIR/MIR
FIR/submmextinction

Dust mass formed in the ejecta is dominated by cold dust

3-2. Dust mass increases with time?
Dust mass estimated fromIR 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 extinctionof 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
Gall+2014, Nature
Dust formed incool dense shell

Dust formed in
the ejecta
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 theformation of dust in theejecta 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??
missingcold dust?

Dust mass
increasingwith 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

Milisavljevic+2013

Orlando+2016

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 fromoptical/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
http://presolargrains.net/
・ 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 …

1-2. Presolar Type X SiC grains○ Presolar SiC 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

Nittler 2003

1-3. Long-lasting questions〇 FactA fraction of presolar SiC grains is highly likely
SN-origin〇 Question
How do these SiC grains form in the ejecta ofcore-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?
44Ti

28Si rich

12C rich

Si isotopes

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 richrequire special condition of ejecta mixing

2-2. Possible formation site of SiC grains in SNe
16O

4He

○ Moderately energetic SNe

12C

Ekin = (3-5)x1051 erg(normal SNe : Ekin ~ 1x1051 erg)

28Si

explosive burning happens at theboundary between O-rich regionand He-rich region➜ producing 12C-rich, 28Si-rich,(44Ti-rich) region## 3(4He) ➔ 12C## 12C + n(4He) ➜ α-elements

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 gasphase C atoms〇 Formation path of grainscool downMore efficient destruction ofC 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

rate coefficients of radiative
association of molecules ki,j

➜ accretion of Si/C atoms〇 This work
‐accretion of SiC molecules‐coagulation
Andreazza+2009

3-1. Formation of SiC molecules
Element# abundance

He0.3

C0.3

O

0.001

Ne0.001

Mg0.002

Si0.2

S

0.19

Ar0.006

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 radiicannot 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 talkWe investigate the formation of SiC grains in theejecta 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 formationof 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