超新星残骸中でのダストの物理進化過程
野沢 貴也
東京大学数物連携宇宙研究機構（ＩＰＭＵ）
共同研究者
小笹 隆司(北大), 冨永望 (国立天文台), 前田啓一(IPMU),
梅田秀之 (東大), 野本憲一 (IPMU/東大)1-1. Introduction○ Dust in SNRs
・ CCSNe are main sources of interstellar dust?
－ formation of dust in the ejecta of SNe－ destruction of dust by the reverse shock➔ What kind and how much amount of dust aresupplied by CCSNe?

・ physical processes of dust in the shocked gas－ erosion by sputtering and collisional heating・ IR thermal emission from shock-heated dust
➔ structure of circumstellar medium and mass-loss
history of progenitor staryoung remnants of CCSNe!

1-2. Cassiopeia A SNR○ Cas A SNR－ age: ~340 yr (Thorstensen et al. 2001)－ distance: d=3.4 kpc(Reed et al. 1995)－ shock radius
forward shock : ~150” (~2.5 pc)
reverse shock : ~100” (~1.7 pc)－ oxygen-rich SNR
dense O-rich fast-moving knots (O, Ar, S, Si, Fe …)
thermal emission from ejecta-dust➔ Mdust = 0.02-0.054 Msun (Rho et al. 2008)－ SN type : Type IIb (Mstar=15-20 Msun)(Krause et al. 2008)

1-3. Aim of our study
・ Formation of dust in the ejecta of Type IIb SN➔ composition, size, and mass of newly formed dust

・ Evolution of dust in the hot plasma in the SNR➔ dynamics and destruction of dust
➔ What fraction of newly formed dust can survive
and is injected into the ISM?

・ Thermal emission from shock-heated dust
➔ comparison with IR observations of Cas A➔ dependence of thermal emission from dust on
the ambient density

1-4. Composition and mass of dust formed
Mass of dust formed

average radius・ various kinds of dust cancondense in each layer

Because of the low gas
density in SN IIb, the radiusof newly fomred dust grains
is small (< 0.01μm)

・ Total dust mass : 0.167 Msun

Dust Evolution in SNRs
T = (1-2) x104 K
nH,0 = 0.1-1 cm-3

He coreFSRSCD2-1. Calculation of dust evolution in SNR○ Model of calculations(Nozawa et al. 2006, 2007)

・ejecta model－ hydrodynamic model fordust formation calculation
・ISM－ homogeneous, Tgas=104 K－ nH = 1.0 and 10.0 cm-3
－ solar composition of gas
・treating dust as a test particle－ erosion by sputtering－ deceleration by gas drag－ collsiional heating

2-2. Dynamics of dust
・ dust model : results of dust formation calculations
・ treating (spherical) dust grains as test particles
・ neglecting the effects of charge of dust

2-3. Erosion rate of dust by sputtering・ da / dt ～ 10-6 nH μm yr-1 cm3 at T > 106 K

2-4. Evolution of dust in Cas A SNR
n=1.0 /cc

n=10.0 /cc

2-5. Time evolution of dust mass
n=1.0 /cc

n=10.0 /cc

Mdust ~ 10-4 Msun at 105 yr

Mdust = 0 Msun at 105 yr

Core-collapse SNe with thin H-envelope cannot be themain sources of dust

3-4. Thermal emission from dust

3-5. Comparison with Cas A observation (1)Data: Hines et al. (2004)
red: with SH
green: without SH

3-6. Comparison with Cas A observation (2)Data: Hines et al. (2004)
red: with SH
green: without SH4-2. Dependence of IR SED on ambient density
ρx1

ρ x 3.3

Md = 0.06 Msun・ dust species ρ x 5
C and Mg2SiO4・ dust size distributionf(a)∝a^-3.5
amin = 0.001 μm
amax = 0.5 μm
・ MC : Msil = 3 : 7

ρ x 10

Data: Hines et al. (2004)
red: ejecta dust
red: with SH
blue: CSM
dust
green:withoutSHSummary1) Small dust grains formed in Type IIb SN cannot survive
destruction by the reverse shock2) IR SED well reflects physical processes of destruction
and stochastic heating of dust
➔ properties (size and composition) of dust
➔ density structure of circumstellar medium3) Model of dust destruction and heating in Type IIb SNR
to reproduce the observed SED of Cas A isMd,eje = 0.06 Msun, Md,ism = 0.03-0.07 Msun
dM/dt = 6.6x10-5 Msun/yr➔ ejecta-dust in denser clump?