2019/11/07

Dust destruction insupernova remnants
Takaya Nozawa(National Astronomical Observatory of Japan)

Are core-collapse supernovae (CCSNe)
dust producers or dust destroyers?
SN 1987A, submm
ALMA, 870 µm

ALMA, 450 µm

HST optical (HI)Chandra, X-ray

SN 1987A, MIR
Gemini T-ReCS
10.36 μm

Cas A, composite
red : MIR

Bouchet+2004
Indebetouw+2014

Cool dust (~20 K) of ~0.5
Msun formed in the ejecta

Forward shock hits
and destroys dustin equatorial ringReverse and forward
shocks, respectively,
destroy the ejecta dust
and interstellar dust1-1. Depletion of gas metals in the ISM
10.1

OC

Mg, Si: 90-95 %SiMg

C, O: 30-70 %0.01

Fe: >99 %Fe0.001

Savage & Sembach (1996, ARAA, 34, 270)

1-1. Depletion of gas metals in the ISM
Most of refractory elements are locked
up1 in interstellar dust grainsO
Mg, Si: 90-95 %C0.1
Dust-to-gas
mass ratio : D ~ 0.01 Si

C, O:
30-70 % of interstellar dust
➜ TheabundanceMg
0.01 is almost saturated
Fe: >99 % Fe0.001
Formation and destruction processes ofinterstellar dust should be balanced out
Savage & Sembach (1996, ARAA, 34, 270)

1-2. Paradox of interstellar dust mass
〇 Injection rate of dust from CCSNe/AGB stars

SFR = stellar
death rate

SNe0.006 Msun/yr

Fraction ofMass fraction Condensationstars evolving of gas ejected efficiency of dust
to SNe/AGBfrom SNe/AGB

AGB stars〇 Destruction rate of interstellar dust by SN shocks 0.004
Msun/yr

SN rateGas mass
swept by aSN shock

Dust-to-gas
mass ratio

Destruction
efficiency of dust

Formation rate of dust in stellar sources islower than destruction rate of dust
➜ Interstellar dust must decrease with time

1-3. What is wrong?
〇 Underestimate dust condensation efficiency- CCSNe eject ~10 Msun gas and ~0.5 Msun dust
fdust,form = 0.05
~90% of dust destroyed by reverse shocks

fdust,form = 0.005 (Mdust,form ~ 0.05 Msun per SN)〇 Overestimate dust destruction efficiency- Mdust, dest ~ 6 Msun per SN ~ 2000 Msun x 0.01 x 0.3
There is uncertainties in destruction efficiency〇 Other sources of interstellar dust?
- RGs, RSGs, sAGB stars, LBVs, WR stars, novae, …
- Grain growth in molecular clouds

2-1. Observed dust mass in CCSNe/SNRs

NIR/MIR
FIR/submm
extinction

Balow+2010

Gomez+2012

Indebetouw+2014

Dust mass formed in the ejecta is dominated by cold dust

2-1. Observed dust mass in CCSNe/SNRs

Optical depth
effects?

Dust mass
increasingwith time?

NIR/MIR
FIR/submm
extinction

Tanaka, TN, et al.
(2012, ApJ, 749, 173)

Dust mass formed in the ejecta is dominated by cold dust

2-2. Mass of SN dust increases with time?
Gall+2014, Nature
Dust formed incool dense shell

Dust formed inthe ejecta
Pre-existing
circumstellar dust
(Van Dyk 2013)

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

2-3. Timescale of grain growth

At 20 yr, the gas density is too low to form
dust grains in the freely expanding ejecta

2-4. Optical depth effects?
Apparent dust mass from IR emission

optically
thick

opticallythin

Dwek+2019- Dust formation can be completed until a few years- The apparent increase in dust mass may be due toopacity effects of dust thermal emission

3-1. Observed dust mass in CCSNe/SNRs
reverse shock
destruction??
Optical deptheffects?

Dust mass
increasing
with time?

??

NIR/MIR
FIR/submm
extinction

Tanaka, TN, et al.
(2012, ApJ, 749, 173)

Dust mass formed in the ejecta is dominated by cold dust

3-2. 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

3-3. Dust mass and size ejected from SNe
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)

3-4. Destruction of dust in Cas A SNR
Dust mass for SNe IIb model

0.008Msun of shocked
warm dust

0.07Msun of unshocked
cool dust

330 yrNozawa+2010- All newly formed grains aredestroyed by reverse shock- FIR observations
Md,cool ~ 0.06 Msun
Tdust ~ 35 K
Balow+2011

Sibthorpe+2010

3-5. Dust destruction in clumpy gas
a = 0.001 a = 0.01

a = 0.1 a = 1 µm

Kirchschlager+2019

3-6. How much dust grains are destroyed?
- Theoretical studies predict that too much dust
grains would be destroyed in the shocked gas➜ destruction fraction : fdest = 0.3-1.0- Dust destruction efficiency heavily depends on
the initial grain size and gas density➜ need the dust formation and destruction
calculations based on 3D ejecta structures- There are uncertainties in the efficiency of dust
destruction by sputtering➜ need the re-evaluation of sputtering yields
theoretically and observationallySummary of this talk
- Are CCSNe producers or destroyers of dust?
➜ Mdust, form = 0.01-0.1 Msun per SN➜ Mdust, dest = 5-10 Msun per SNR- When do dust grains form in the SN ejecta?
➜ observationally : ~20 yr (increase with time)➜ theoretically : ~2-3 yr- What fraction of dust can be destroyed by thereverse shock?
➜ fdest = 0.3-1.0 (surviving dust mass: fsurv = 0-0.7)➜ need the 3-D dust formation/destruction
and re-evaluation of sputtering yield