Cas A 超新星残骸中のダストの一生
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 (甲南大), 梅田秀之 (東大),前田啓一, 野本憲一 (IPMU), Oliver Krause (MPIA)
Nozawa et al. (2010), ApJ, 713, 356(arXiv: 0909.4145)

1-1. Introduction○ Cassiopeia A SNR－ distance : d=3.4 kpc (Reed et al. 1995)－ age : t=330 yr (Thorstensen et al. 2001)－ ejecta mass : Meje=2-4 Msun (e.g. Willingale et al. 2002)－ SN type : Type IIb (Krause et al. 2008)(generated from a supergiant that had lost most of H-envelope)－ thermal emission from ejecta-dust (mainly silicates)➔ Mdust = 0.02-0.054 Msun (Rho et al. 2008)
・ formation process of dust in the ejecta
・ physical processes of dust in the shocked gas➔ erosion by sputtering and collisional heating
・ CCSNe are important sources of dust?

1-2. Aim of our study
・ Birth of dust in the ejecta of Cas A
dust formation calculation based on SN II model➔ composition, size, and mass of newly formed dust
➔ dependence of dust formation process on typesof SNe (on the mass of H-envelope)・ Brightening of dust in the shocked hot gas
dust evolution calculation in the SNR➔ IR emission from the shock-heated dust
➔ comparison with IR observations of Cas A・ Fate of dust in Cas A SNR➔ How much mass of the dust grains in Cas A cansurvive and can be injected into the ISM?

2-1. Dust formation calculation in the ejecta○ Dust formation calculation－ non-steady nucleation andgrain growth theory(Nozawa et al. 2003)○ SN IIb model(SN1993J-like model)－ MH-env = 0.08 Msun
MZAMS = 18 Msun
Meje = 2.94 Msun
－ E51 = 1－ M(56Ni) = 0.07 Msun
〇 SN II-P model : MH-env = 13 Msun, MZAMS = 20 Msun, E51 =1(Umeda & Nomoto 2002)

2-2. Birth of dust in the ejecta of Cas A
mass distribution

condensation time

－ condensation time of dust
300-700 d after explosion－ total mass of dust formed
・ 0.167 Msun in SN IIb
Mc=0.07 Msun
Msilcate=0.08 Msun
・ 0.1-1 Msun in SN II-P

2-3. Dependence of dust radii on SN typeSN IIb

SN II-P

0.01 μm

SN Ib (SN 2006jc)(Nozawa et al. 2008)

The radius of dust formedin H-stripped SNe is small－ SN IIb and SN Ib/Ic without
massive H-env➔ adust < 0.01 μm－ SN II-P with massive H-env➔ adust > 0.01 μm

3-1. Calculation of dust evolution in SNRs
○ Dust evolution calculations (Nozawa et al. 2006, 2007)－ spherical symmetric hydrodynamic calculation based on
the ejecta model of the SN IIb－ treating dust as a test particle
・ erosion by sputtering
・ deceleration by gas drag・ collsional stochastic heating－ density profile of CSMnH(r) = nH,1 (r / r1)-2 /cc= 1 /cc for nH < 1 /cc
r1 = r(at 10 yr) = 1.2x1018cm
nH,1 = 30, 120, 200 /cc(➔ dM/dt = 2.0, 8.0, 13x10-5 Msun/yr for vw=10 km/s)

3-2. Time evolution of IR SEDs in Cas A SNR

nH,1=30 /cc

nH,1=120 /cc

Dust evolutions andthus IR SEDs in SNRs
strongly depend on thegas density in the CSM
nH,1=200 /cc

3-3. Comparison with observations of Cas A－ MIR, d = 0.008 Msun
(Mshocked, d ~ 0.1 Msun)－ dM/dt = 8x10-5 Msun/yr➔ dM/dt ~ 2x10-5 Msun/yr for
Cas A (Chevalier & Oishi 2003)➔ dM/dt = (3-4)x10-5 Msun/yrfor 93J (Suzuki & Nomoto1995)

3-4. Contribution from circumstellar dust
〇 CSM dust model

C・ dust species
C and silicate
・ dust size distributionf(a) ∝ a^-3.5
amin = 0.001 μm
amax = 0.5 μm
・ dust-gas ratio: parameter
Silicate

・ CSM dust cannot
compensate the flux
densities at λ > 50 μm
green: ejecta dust
blue: CSM dust

3-5. Contribution from unshocked dust

Sibthorpe et al. 2009

observed IR SED canbe well reproduced！
↑・ Md,warm ~ 0.008 Msun
・ Md,cool ~ 0.07 Msun
with Tdust ~ 40 K

AKARI reduced 90μm image➔ centrally peaked cooldust component↓
Md,cool = 0.03-0.06 Msun
with Tdust = 33-41 K

4-1. Fate of dust in Cas A SNR
nH,1=120/cc

・ All of the dust grains in Cas A would be destroyed inthe shocked gas within the SNR before ~2x104 yr➔ small grain size of newly formed dust
➔ early arrival of the reverse shock at the He coreH-deficient SNe may not be major contributors of dust
・ 0.01-0.8 Msun of dust survive for SNe II-P (Nozawa+2007)

Summary1) Birth of Dust in the ejecta of Cas A
Dust formed in Cas A was formed at 300-700 days after
the explosion with adust < 0.01 μm and Mdust = 0.167 Msun

2) Brightening of dust in the shocked hot gas
Model of dust destruction and heating in Type IIb SNR
can reasonably reproduce the observed SED of Cas A;
Md,warm = 0.008 Msun, Md,cool = 0.07 Msun
dM/dt = ~8x10-5 Msun/yr3) Fate of dust in Cas A SNR
Small dust grains in Cas A will be completely destroyedin the shocked gas without being injected into the ISM