2017/12/22

超新星ダストの形成と銀河ダストの物理
化学進化 －コンセンサスと課題－(Formation of SN-dust and Evolution of dustin galaxies －consensus and issues－)

野沢 貴也 （Takaya Nozawa）
National Astronomical Observatory of Japan

Special thanks:
Hirashita Hiroyuki (ASIAA), Hideyuki Umeda (Univ. of Tokyo),Takashi Kozasa, Asao Habe (Hokkaido Univ.),
Asano, S. Ryosuke, Takeuchi, T. Tsutomu (Nagoya University),
Keiichi Maeda (Kyoto Univ.), Masaomi Tanaka (NAOJ),
Ken’ichi Nomoto, Fukugita Masataka (Kavli IPMU)

1-1. Discovery of massive dust at z > 5The far-infrared and submm observations have confirmed thepresence of dust in excess of 108 Msun in 30% of z > 5 quasars
108-109 Msunof dust in
SDSS J1148+
5251 at z=6.4
Leipski+2010~106 Msun ofdust in a galaxy
at z = 8.4
Laporte+2017‐In the MW, AGB stars are considered to be major dust
sources ➜ too old to supply dust in the early universe‐0.1 Msun of dust per SN is needed to explain massive
dust at high-z (e.g. Morgan & Edmunds 2003; Maiolino+2006; Dwek+2007)

1-2. Depletion of gas metals in the present ISM10.1

OCMg, Si: 90-95 %SiMg

C, O: 30-70 %0.01
Fe: >99 %Fe0.001

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

1-3. Average extinction curve in the Milky Way〇 MRN dust model(Mathis, Rumpl, & Nordsieck 1977)- dust composition:
silicate and graphite- size distribution: power-lawn(a) ∝ a^{-q} with q=3.5,
amax = 0.25 μm
amin = 0.005 μm- mass ratio: Msil / Mgra ~ 2

astronomical silicate (Draine & Lee 1984)- hypothetical material to account for observed spectra from
UV to infrared (i.e. its optical constant is artificial)assumed chemical composition： Mg1.1Fe0.9SiO4

2-1. Key questions for dust formation in SNe
1. How much dust grains form?

2. What is the size distribution of dust?

3. When do the majority of grains form?

2-2. Observed dust mass in CC-SNe/SNRs
reverse shock
destruction??

??
NIR/MIR
Matsuura+2011
FIR/submm
Balow+2010
extinction

Gomez+2012

Dust mass formed in the ejecta is dominated by cold dust

2-3. Properties of dust ejected from SNe II-P
Nozawa+07, ApJ, 666, 955

SNe II

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)

2-2. Observed dust mass in CC-SNe/SNRs
reverse shock
destruction??
missing
cold dust?

Dust mass
increasingwith time?

??

NIR/MIR
FIR/submm
extinction

Dust mass formed in the ejecta is dominated by cold dust

2-4. Dust mass increases with time?
Dust mass estimated fromIR SEDs
Gall et al. (2014, Nature)Most of dust grains(> 0.1 Msun) form at~20 yr post-explosion
Evolution of dust mass in SN
1987A derived from extinctionof optical emission lines
Bevan & Barlow (2016)

2-5. Interpretation of Gall et al. (2014) paper
Gall+2014, Nature
Dust formed incool dense shell

Dust formed in
the ejecta
Pre-existing
circumstellar dust

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

2-6. Timescale of grain growth

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

2-7. Key questions for dust formation
1. How much dust grains form?
‐theoretical works ➜ 0.1-1 Msun
‐FIR/submm obs. ➜ 0.1-1 Msun

2. What is the size distribution of dust?
‐theory ➜ relatively large grains (>0.1 µm)‐obs.➜ very large (~1 µm) at the dust formation

3. When do the majority of grains form?
‐theory ➜ ~1-3 yr (within 5 yr; earlier is better)‐obs. ➜ ~20 yr (dust mass gradually increases with time)3-1. Cycling of interstellar dust in the universe
ビッグバン

分子雲分子雲中でのダストの成長

星間空間中でのダストの破壊・変性

原始惑星系円盤星の誕生

惑星系の形成
星間空間

超新星爆発
星の進化
星間空間へのダスト供給

晩期型星

3-2. Dust evolution model in a galaxy (1)Asano+2013, 2014

‐one-zone closed-box model (no inflow and no outflow)‐star formation rate (SFR)
Schmidt law with n = 1: SFR(t) = Mgas(t)/τSF with τSF = 5 Gyr‐initial mass function (IMF)
Salpeter IMF: φ(m) = m-q with q=2.35 for Mstar = 0.1-100 Msun
‐two-component dust modelgraphite (carbonaceous grains)astronomical silicate (silicate and the other grains species)‐two-phase ISM
WNM (warm neutral medium): T = 6000 K, n = 0.3 cm-3
CNM (cold neutral medium): T = 100 K, n = 30 cm-3
➜ ηWNM = ηCNM = 0.5

3-3. Dust evolution model in a galaxy (2)Asano+2013, 2014

‐mass evolution of dust ΔMd(a,t) with radii between a and a+daxSFR(t), astration
dust production by SNe II and AGB stars

shock destruction
grain growth

shattering

coagulation

3-4. How dust mass increases in the ISM
Shattering and grain growthnecessary for achieving theobserved high dust content

Growth of small grains via
accretion of gas in the MCs
Asano+2013

Ejection of large grainsfrom SNe/AGB stars

Production of small grains
via shattering in the ISM

3-5. Evolution of extinction curves in galaxies
dust amount

grain size distribution

extinction curve

MRN

Asano+2014‐early phase : formation of dust in SNe II and AGB stars➔ large grains (>0.1 μm） are dominant ➔ flat extinction curve

Asano+12‐middle phase : shattering, grain growth due to accretion of gas metal➔ small grains (< 0.03 μm） are produced ➔ steep extinction curve‐late phase : coagulation of small grains➔ shift of peak of size distribution ➔ making extinction curve flatter3-6. Reproducing the MW extinction curve‐two-phase ISM
・ WNM (T = 6000 K, n = 0.3 cm-3)

WNM=0.5
CNM=0.3
MC=0.2

・ CNM (T = 100 K, n = 30 cm-3)‐three-phase ISM
・ WNM (T = 6000 K, n = 0.3 cm-3)
・ CNM (T = 100 K, n = 30 cm-3)・ MC (molecular clouds)➜ T = 25 K, n = 300 cm-3Nozawa+2015- three-phase ISM model including the MC phase can reproduce
the average extinction curve in the MW- ISM phase is one of the important quantities in constructing theevolution model of interstellar dust

3-7. Explaining massive dust in high-z quasars‐two-phase ISM:
WNM=0.3 and MC=0.7‐τSF = 0.5 Gyrhigh-z quasar host: starburst galaxies➜ indicating a high fraction of MC
MH2/MH,total ~ 0.7-0.97 (Calura+2014)

Nozawa+2015

4-1. Issues of dust evolution model (1)〇 What is property of C grains?
‐Asano dust evolution model
high-z : amorphous carbon
present : graphite

silicate and graphite (am.car)➜ three-component dust model
consisting of silicate, am.car, PAH## cannot explain the SMC dust

Nozawa+2015

Asano+2014

4-2. Issues of dust evolution model (2)〇 Too much (small) C grains

Nozawa+2015‐stronger (sharper) 2175A bumpthan observed in the MW➜ larger amount of (small) C grains‐dust evolution model
efficient grain growth in MCs➜ almost all C atoms (>90%) accrete
onto dust grains‐depletion of C atoms in the ISM
50-70% of C locked in dust grains
Aoyama+2017; Hou+2017

4-3. Issues of dust evolution model (3)〇 Gas accretion onto dust
grains in MCs really works?
‐selective accretion (coagulation)
Si, Mg, Fe, O ➜ silicate grainsC➜ carbon grains## heterogeneous dust grain model(Jones+2013, 2016, 2017)‐formation of ice mantle in MCs➜ ice mantle would form before
efficient accretion of metal gas(Ferrara+2016)## high CMB temperature would
suppress grain growth at high z
Jones+2013

4-4. Issues of dust evolution model (4)〇 Fe-missing problem

Fe 0%‐two-component dust model
Si, Mg, Fe, O ➜ silicate grains## astronomical silicate: Mg1.1Fe0.9SiO4

Fe 1%Brommaert et al. (2014)‐no evidence for Fe-rich silicate grains‐no evidence for formation of pure Fe
grains in Type Ia SNe

Herschel 100 µm image

Tycho## 99% of Fe locked up in the ISM‐Fe atoms must be incorporated into
dust grains in dense MCs (Dwek 2016)
Gomez+2012

4-5. Consensus and issues for dust evolution
Consensus
Grain growth is needed to account for a large amountof interstellar dust in both high-z and nearby galaxies(Draine2009; Michalowski+2010; Gall+2011a, 2011b; Pipino+2011;
Mattsson+2011; Inoue2011; Valiante+2011, 2014; Kuo & Hirashita 2012;
Asano+2013a, 2013b, 2014; Calura+2014; Dwek+2014; Nozawa+2015;
Michalowski+2015; Aoyama+2017; Hou+2017; Hirashita & TN 2017)

Issues‐Grain growth efficiently takes place in the MCs?
‐Grain growth is an important process to regulate thecomposition, size, and mass of interstellar dust?
‐Grain growth naturally explain the properties ofinterstellar dust extracted from observations?