2016/02/29

Dust formation and ejection
by supernovae
Takaya Nozawa(National Astronomical Observatory of Japan)

Contents:- Introduction- Production of dust in the ejecta of supernovae- Ejection of dust from the supernova remnants- Formation and survival of presolar grains

1-1. Introduction〇 Supernovae (SNe) are major sources of dust?
- abundant metal (metal : N > 5)
- low temperature (T < ~2000 K)- high density (ni > ~106 cm-3)- mass-loss windsof AGB stars- expanding ejectaof SNe‐ contribution of dust mass from AGB stars and SNe
N(SNe) / N(AGB stars) ~ 0.05-0.1 (Salpeter IMF)

Mdust = 0.01-0.05 Msun per AGB star (e.g., Zhukovska & Gail 2008)
Mdust = 0.1-1.0 Msun per SN (e.g., Nozawa+2003, 2007)‐ huge amounts of dust grains (>108 Msun) at redshift z > 5➔ 0.1 Msun of dust per SN is needed to be ejected (Dwek+2007)
what composition, size, and mass of dust are ejected by SNe?

1-2. Summary of observed dust mass in CCSNe

missing cold dust?

young SNRs

Matsuura+2011

Type II-P SNeBalow+2010

Gomez+2012

swept-up IS dust?

Far-IR to sub-mm observations are essential for revealing
the mass of dust grains produced in the ejecta of SNe

1-2. Summary of observed dust mass in CCSNe

missing cold dust?

young SNRs

Type II-P SNe

swept-up IS dust?

There are increasing pieces of evidence that massive
dust in excess of 0.1 Msun is formed in the ejecta of SNe

1-3. Formation and processing of dust in SNe
Nozawa 2014, Astronomical Herald~1-3 yrs~1000 yrs

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

1-4. Achievement and issues on SN dust
〇 What we have understood isCore-collapse supernovae can produce a large amountof dust in excess of ~0.1 Msun in the expanding ejecta〇 What we have not understood yet is1) when the observed massive dust was formed?
➜ Cause of difference in dust mass in MIR and FIR2) What composition and size distribution of dust are?
➜ Critical to the yield of dust finally ejected from SNe2. Formation of dust in the ejectaof supernovae

2-1. Dust formation in Type II-P SNe
Nozawa+2003, ApJ, 598, 785〇 SN model (Population III SNe) (Umeda & Nomoto 2002)‐SNe II ： MZAMS = 13, 20, 25, 30 Msun (E51=1)
after 600 days

‐layered elemental distribution in the metal-rich He core‐no mixing of elements within the He-core‐gas density: ρ ~ 10-14-10-13 g/cm3 ➜ n ~ 108-1010 /cm3

2-2-1. Grain species considered in this study〇 dust formation theory‐nucleation‐grain growth
taking account of chemical
reaction at condensation(Kozasa & Hasegawa’87)# key species：
gas species with theleast collision frequency
among reactants

key species controls thekinetics of the nucleationand grain growth2-2-2. Nucleation rate
Steady-state nucleation rate: Js

Supersaturation ratio: S

2-2-3. Basic equations for dust formation
・ Equation of mass conservation

・ Equation of grain growth

Growth rate is independent of grain radius

2-3. Dust formed in Type II-P SNeaverage radius

0.01 μm

C / O < 1 ➔ all C atoms are locked up in CO
C / O > 1 ➔ all O atoms are locked up in CO
condensation time‐a variety of grain species cancondense according to elemental
composition in each layer‐ condensation time:
300-600d after explosion‐ average grain radii: >~0.01 μm
Nozawa+03, ApJ, 598, 785

2-4. Size distribution of newly formed dust
Nozawa+2003, ApJ, 598, 785‐C, SiO2, and Fe grains have lognormal-like size distribution,
while the other grains have power-law size distribution‐Size distribution summed up over all grain species is roughly
described by a broken power-law with the index of -2.5 and -3.5
‐Size distribution of dust in mass has a peak around 0.1-1 µm

3. Destruction of dust grains bySN reverse shocks
T = (1-2)x104 K
nH,0 = 0.1-1 cm-3

He coreFSRSCD

3-1-1. Time evolution of SNRs

3-1-2. Dynamics of dust

3-1-3. Erosion rate of dust by sputtering3-2. Temperature and density of gas in SNRs
Nozawa+07, ApJ, 666, 955

Model : Mpr= 20 Msun (E51=1)
nH,0 = 1 cm-3

Downward-pointing arrows:
forward shock in upper panel
reverse shock in lower panel
The temperature of the gas
swept up by the shocks➔ 106-108 K↓
Dust grains residing in theshocked hot gas are erodedby sputtering3-3. Evolution of dust in SNRs
Model : Mpr= 20 Msun (E51=1), nH,0 = 1 cm-3
dust trajectories

The evolution of dust heavily
depends on the initial radiusand compositionaini = 0.01 μm (dotted lines)➔ completely destroyedaini = 0.1 μm (solid lines)➔ trapped in the shellevolution ofdust radiiaini = 1 μm (dashed lines)➔ injected into the ISM
Nozawa+07, ApJ, 666, 9553-4. Dust mass and size ejected from SNe II
Nozawa+07, ApJ, 666, 955

SNe II-P

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)

3-5. Conclusions from theoretical works
1) When the observed massive dust was formed?
➜ within 3 years after SN explosion
2) What composition and size distribution of dust are?
‐composition: carbon, silicate, oxide, pure iron …
‐size (distribution)- at the formation ➜ a few A to ~1 µm (broken power-law)- after destruction ➜ biased to larger than ~0.1 µm‐dust mass
- at the formation: 0.1-1.3 Msun
➜ after destruction: 0.07-0.8 Msun

4. Formation and survival ofpresolar grains

4-1. No formation of SiC in the calculations

The earlier formation of C grains
prevents condensation of SiC

4-2. Isotopic composition of presolar oxides○ Oxygen isotopic composition of presolar oxide grainspresolar Al2O3 grains

Group 2
AGB stars

Choi+1998

Group 1RGsGroup 3 / 4
unspecifiedor SNe?

SNeA few particles
of presolar Al2O3
Clayton & Nittler 2004
grains with radii > 0.25 µm
are believed to have been produced in the ejecta of SNe4-3. Why we focus on presolar Al2O3 grains?
○ Evidence for Al2O3 formation in SNe‐ Infrared spectra of Cassiopeia A (Cas A) SNR➜ Al2O3 is one of the main grain species(Douvion et al. 2001; Rho et al. 2008)〇 Dust formation calculations‐ the first condensate among oxide➜ sizes of Al2O3 grains : < ~0.03 µm

Douvion+2001(e.g., Nozawa+2003; Todini & Ferrara+2001)

Nozawa+2003

destructionin SNRs

Nozawa+2007

4-4. Formation condition of presolar Al2O3
Nozawa+2015, ApJ, 811, L39
density of Al atoms at dust
formation must be > ~109 cm-3➜ at least 10 times higher gas
density than those predictedby 1-D SN models

Submicron-sized presolar Al2O3 grains identified as
SN-origin were formed in dense clumps in the ejecta

4-5. Newly formed grains can survive in SNR?
Model of the calculation:
MSN= (3 + 12) Msun, Eexp=1.8x1051 erg,nISM = 1 cm-3

Nozawa+2015, ApJ, 811, L39

Evolution of dust in SNRs
depends on the initial radii- aini < 0.01 μm➔ completely destroyed- 0.02 μm < aini < 0.1 μm➔ eroded in dense shell- aini > 0.1 μm➔ injected into the ISM

4-6. Lifetimes of presolar grains in the ISM○ Lifetimes of large grains against
shattering in the ISM

Hirashita, TN+2016,
accepted, arXiv:1602.07094‐Lifetimes of large grains increase
with their initial radii‐SiC has a much longer timescale ofdestruction than silicate and graphite

4-7. Summary1) SiC grains cannot form in the calculations because
earlier formation of C grains consumes up the carbon
atoms available for the formation of SiC.
2) Presolar Al2O3 grains with radii above 0.25 µm can beformed only in the gas with more than 10 times higher
density than those estimated by 1-D SN models.
➜ indicating the presence of dense clumps in the SN ejecta

3) Lifetimes (shatterring timescale) of SiC grains above
0.1 µm in the ISM are longer than 10^8 year.

## The measured sizes of presolar grains are powerfulprobes for constraining the physical conditions andprocesses in which they experienced.