2010/12/16

Properties of interstellar andcircumstellar dust as probed by mid-IR
spectroscopy of supernova remnants(超新星残骸の中間赤外分光から探る星間・星周ダスト)

Takaya Nozawa(IPMU, Univ. of Tokyo)
Masaomi Tanaka, Keiichi Maeda (IPMU)
Itsuki Sakon (Univ. of Tokyo)

1-1. Motivation : unsolved problems
・ How has the cosmic dust evolved in galaxies?
－ origin of dust : SNe, AGB stars, any other sources－ destruction of dust : SN blast wave

・ Galactic dust model
MRN model (Mathis et al. 1977, Draine & Lee 1984)－ carbonaceous : graphite or amorphous?
－ silicate : astronomical silicate?
－ size distribution : f(a) ∝ a^-3.5 (0.005 μm < adust < 0.25 μm)

・ SMC and LMC dust model－ only silicate grains (Pei 1992)－ small grains are abundant (Weingartner & Draine 2001)

1-2. Why dust in SNRs?
・ interstellar dust in diffuse medium
Tdust ~ 15-30 K ➔ far-IR emission (> 50 μm)
poor information on composition and size of dust

・ interstellar dust swept up by SNRs
Tdust ~ 50-200 K ➔ mid-IR emission (5-50 μm)－ 9.8 μm and 18 μm features of silicate－ 30 μm broad feature of graphite➔ dust composition# shocked dust is destroyed by
sputtering in the hot plasma－ dust temperature➔ gas density ➔ dust radius➔ dust destruction efficiency

1-3. Strategy chart
initial dust size distribution
pre-shock dust-to-gas ratio

mid-IR spectraof SNRs

shocked dust massand size distribution

dust temperature

dust composition

destruction
rate of dust

gas density(X ray obs.)(if CSM origin)mass-loss rate and stellar mass of the SN progenitor

2-1. Spitzer observations of SNRs in LMCType Ia

24 μm 70 μm

HαX-ray

Borkowski et al. (2006)

DEM L714400 yr

Tdust = 55-65 K
Mdust = 0.034 Msun
ne = 2.7 cm-30548-70.4
7100 yr

Tdust = 53-62 K
Mdust = 0.0018 Msun
ne = 2.0 cm-30509-67.5
400 yrTdust = 66-70 K
Mdust < 0.0011 Msunne > 1.6 cm-30519-69.0
600 yrTdust = 72-86 K
Mdust < 0.0033 Msunne > 3.4 cm-3

24μm / 70μm flux ratio, LMC dust model➔ dust-to-gas mass ratio is less than 0.3 %see also Williams et al. (2006) for CCSN remnants in LMC

2-2. AKARI observations of G292.0+1.8
Lee, ..,TN, .. et al. (2009)

・ O-rich SNR (Type II-P)・ SNR age : ~3000 yr

IR three-color image

10μm20μm

・ Galactic size distribution
・ nH,0 = 0.5 cm-3
・ silicate (CSM origin)・ Tdust ~ 45-65 K・ dust-to-gas ratio ~ 0.1%

2-3. IR observations of middle-aged SN 1987A
Dwek et al. (2008)

Bouchet et al. (2006)

・ O-rich SNR (Type II-P)・ SNR age : ~20 yr

・ ne = (0.3-1)x104 cm-3
・ Tdust ~ 180 K
・ silicate (CSM origin)
・ 0.02 μm < adust < 0.2 μm
・ dust-to-gas ratio ~ 0.3%
see also Dwek et al. (2010)

3-1. Temperature of dust in the hot plasma
Dwek et al. (2008)

・ dust temperature well reflects the plasma density

3-2. Stochastic heating of small grains
Cas ANozawa et al. (2010)

dust formation calculations
・ silicate dominated・ adust < ~0.01 μmemission spectra at shorter
mid-IR are good probes ofabundance of small grains!
・ aC and silicate (Mg2SiO4)・ dust size distributionf(a) ∝ a^-3.5
amin = 0.001 μm
amax = 0.5 μm
・ dust-gas ratio: parameter3-3. Dust in Cas A

AKARI corrected 90 μm image

Nozawa et al. (2010)

・ Md,warm ~ 0.008 Msun
・ Md,cool ~ 0.072 Msun
with Tdust ~ 40 K・ mass-loss rate
dM/dt = 8x10-5 Msun/yr

AKARI observation
Md,cool = 0.03-0.06 Msun
Tdust = 33-41 K(Sibthorpe et al. 2010)

Herschel observation
Md,cool = 0.075 Msun
Tdust ~ 35 K
(Barlow et al. 2010)

4. AKARI observations of SN 2006jc
Sakon, .., TN, .., et al. (2009)

800K aC
800K aC

820K silicate

320K aC・ dust species
newly formed hot aC
CSM origin cool aC・ progenitor : WR star
simultaneous observations
at 5-40 μm are necessary!

5. Detectability of IR emission from SNRs
IR SED of Cas A-like SNR

IR SED of G292-like SNR(SNR age = 330 yr, Tdust ~ 100 K)(SNR age = 3000 yr, Tdust ~ 50 K)・ enable to obtain the IR spectra of individual parts ofSNRs in LMC and SMC・ possible to detect the mid-IR emission from shocked
dust in very nearby (~a few Mpc) extragalactic SNRs

Summary on IR spectroscopy of SNRs
・ Targets for accomplishing this science－ SNR age: up to ~10000 yr－ SN type : both SNe Ia and CCSNe－ SNRs in MW, LMC, SMC, nearby galaxies

・ What we learn from IR spectroscopy of SNRs
－ composition and size distribution of ISM/CSM dust

－ dust-to-gas mass ratio, dust destruction efficiency－ gas density around SNe ➔ mass-loss rate of progenitor

・ Instrument for accomplishing this science－ mid-IR spectroscopy at 5-40 μm is essential－ low/mid-resolution, simultaneous observations