2014/02/18

Origin and Nature of Dust Grainsin the Early Universe
Takaya Nozawa(Kavli IPMU, University of Tokyo)
Main collaborators:
T. Kozasa, A. Habe (Hokkaido University)
K. Maeda (Kyoto University), K. Nomoto (Kavli-IPMU)
H. Umeda (University of Tokyo), H. Hirashita (ASIAA)
R. S. Asano, T. T. Takeuchi (Nagoya university)

1. Introduction

1-1. Discovery of massive dust at z > 5
The far-infrared and submm observations have confirmed thepresence of dust in excess of 108 Msun in 30% of z > 5 quasars

SDSS J1148+5251 at z=6.4‐ cosmic age : 890 Myr‐ stellar mass : ~1011 Msun
‐ SFR : ~3000 Msun/yr (Salpeter IMF)
‐ gas mass : ~3x1010 Msun (Walter+2004)‐ IR luminosity : (1-3)x1013 Lsun
‐ dust mass : (2-7)x108 Msun
‐ dust-to-gas mass ratio : ~0.01

stellaremission

dustemission‐ metallicity : ~solar ~ 0.02
‐ dust-to-metal mass ratio : ~0.5
Leipski+2010, A&A, 518, L34

1-2. What are dust sources in high-z quasars?
・ Type II supernovae (SNe II)‐dust evolution model: >0.1-1 Msun per SN(Morgan & Edmunds 2003; Maiolino+2006; Dwek+2007)‐theoretical studies of dust formation: ~0.1-1.0 Msun per SN(Todini & Ferrara 2001; Nozawa+2003, 2007; Bianchi & Schneider 2007)

・ AGB stars + SNe

Dwek & Cherchneff (2011)‐AGB stars supply more dust grains thanSNe II (Valiante+2009; Dwek & Cherchneff 2011)‐dust formation calculation: 0.01-0.05 Msunper AGB star (Zhukovska & Gail 2008)## no efficient dust formation in metal-poor AGB stars (Di Criscienzo+2013)

・ Grain growth in molecular clouds + AGB stars + SNe(Draine 2009; Michalowski+2010; Gall+2011a, 11b; Pipino+2011;
Mattsson+2011; Valiante+2011; Inoue 2011; Kuo & Hirshita 2012)

1-3. Sources of dust in 5 < z < 6.4
Michalowski+2010, A&A, 522, 15

Rapid grain growth is required for at least 3 out of 9 quasars at z > 5
Mdust = Mstar x fSN x Ydust= 1.5x108 Msun (Mstar / 1011 Msun) (fSN / 0.3) (Ydust / 0.005)

fSN = MSN / Mstar ~ 0.3 for Salpeter IMF
Ydust = mdust / mSN ~ 0.005 for mdust=0.1 Msun for mSN=20 Msun

1-4. Extinction curves for z=6.4 quasars
Maiolino+2004, Nature, 431, 533

SDSS J1048+4637 at z=6.2 :broad absorption line (BAL) quasars➔ different dust properties fromthose at low redshift1-5. Extinction curves at 3.9 < z < 6.4
high-z quasar extinction curves

Gallerani+2010, A&A, 523, 85

GRB 050904 at z=6.3

Stratta+2007, ApJ, 661, L9

GRB 050525A
at z=0.6
Heng+2008, ApJ,681, 1116

1-6. Summary of Introduction‐ There is clear evidence for a huge amount of dust grains at z > 5,but the main sources of such massive dust remain to be specified➔ SNe II evolving from short-lived massive stars must be sourcesof dust at the very early times of galaxy evolution➔ grain growth in molecular clouds seems to be needed to explain
the dust content observed for high-z quasars‐ Extinction curves at high z are different from those at low z➔ properties (composition & size) of dust at z > 4 are likely to bedifferent from those at low z➔ high-z quasars and GRB afterglows are good targets to probe
the extinction curves in their host galaxies## there might be possibility that we are seeing the properties of## dust in local environments around the quasars and GRBs

2. Properties of dust ejected fromPopulation III SNe II and PISNeDust Formation in the ejecta of SNe
at ~1 days
He-coreH-envelope

NS or BH
He–layer (C>O)
O–Ne-Mg layer
Dust formation
Si–Satlayer~1-3 years
afterlayer
explosion
Fe–Ni2-1. Dust formation in primordial SNe
Nozawa+2003, ApJ, 598, 785〇 Population III SNe model (Umeda & Nomoto 2002)‐SNe II ： MZAMS = 13, 20, 25, 30 Msun (E51=1)‐PISNe ： MZAMS = 170 Msun (E51=20), 200 Msun (E51=28)‐nucleation and grain growth theory (Kozasa & Hasegawa 1987)‐no mixing of elements within the He-core‐complete formation of CO and SiO

2-2. Dust formed in Type II-P SNeaverage radius

0.01 μm

condensation time‐a variety of grain species cancondense according to elemental
composition in each layer‐ condensation time:
300-600d after explosion‐ average grain radii: >~0.01 μm
Nozawa+03, ApJ, 598, 785

2-3. Size distribution of newly formed dust
Nozawa+2003, ApJ, 598, 785‐C, SiO2, and Fe grains have lognormal-like size distribution,
while the other grains have power-law size distribution‐The composition and size distribution of dust formed are almost
independent of types of supernova## average grain radius is smaller for PISNe than SNe II-P

2-4. Total mass of dust formed in the ejecta
SNe II‐Total mass of dust is higher for a higher progenitor mass (MZAMS)
SNe II ： mdust = 0.1-1.5 Msun, mdust / mmetal = 0.2-0.3PISNe ： mdust = 10-30 Msun, mdust / mmetal = 0.3-0.4‐almost all Fe, Mg, and Si are locked up in dust grains, whilemost of C and O remain in the gas-phase (such as CO)➔ dust-to-metal mass ratio is not high for SNe II

Evolution of dust in SN remnants
T = (1-2)x104 K
nH,0 = 0.1-1 cm-3He coreFSRSCD2-5. Evolution of dust in SNRs
Nozawa+07, ApJ, 666, 955

Model : Mpr= 20 Msun (E51=1)
nH,0 = 1 cm-3
Dust grains in the He core
collide with reverse shockat (3-13)x103 yr
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 shellaini = 1 μm (dashed lines)➔ injected into the ISM

2-6. Dust mass and size ejected from SN II-PPISNe
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 (> 0.01 μm)

Nozawa+07, ApJ, 666, 955
at time of dust formation

after destruction of dust
by reverse shock2-7. Summary of dust production in Pop III SNe‐Various grain species can condense in the ejecta➔ almost all Fe, Mg, and Si are locked up in grains‐The fate of newly formed dust within SNRs strongly
depends on the initial radii and compositions‐The size distribution of dust surviving the destructionin SNRs is weighted to relatively large size (> 0.01 μm).

‐The total mass of dust injected into the ISM decreases
with increasing the ambient gas densityfor nH,0 = 0.1-1 cm-3
SNe II-P ➔ Mdust = 0.1-0.8 Msun
➔ significant contribution to dust budget at high z

3. Extinction curves expected inhigh-z galaxies

3-1. Flattened extinction curves at high-z
Hirashita, TN+08, MNRAS, 384, 1725

Gallerani+10, A&A, 523, 85

z=5.8, BAL

z=5.1, BAL

Maiolino+04, A&A, 420, 889

3-2. Discussion on high-z extinction curves
average radii of dust grains ejected from SNe are large (~0.1 μm)‐extinction curve expected from SN dust is flat‐consistent with a tendency that the extinction curves observedfor high-z objects are flat
➔ these seem to support the idea that SNe II are the main dust
sources in the early universe〇 concerns and questions‐too flat extinction curves, compared with the observations?
‐only SN dust can explain a massive amount of dust observed
at high redshifts?
‐grain growth is needed? (which enhances the size of grains)➔ extinction curves become much flatter?
➔ grain growth can take place efficiently in such an early epoch?

3-3. Rapid grain growth at high-z objects?
## grain growth : accretion of gas-phase metals onto pre-existing dust,##
which works more efficiently in denser molecular clouds〇 timescale of grain growth (gas accretion timescale onto dust)τacc = [ (1/a)(da/dt) ]-1 = [ (1/a) αs nmetal V0 <v> ]-1~ 5x107 yr (αs / 0.2)-1 (a / 0.01μm) (Z / 0.02)-1 (ngas / 30cm-3)-1➔ grain growth is more efficient for higher metallicity andsmaller grains〇 high-z quasars (age: ~0.5 Gyr)‐metallicity ~ solar‐average radius of SN dust ~ 0.1 µm

τacc ~ 5x108 yr ➔ grain growth is not effective??

3-4. Effect of size distribution on grain growth
w/o shattering

shattering

Kuo & Hirashita+12,
MNRAS, 424, L34

w/ shattering‐w/o shattering : grain growth becomesefficient at super-solar metallicity‐w/ shattering : grain growth becomesefficient at sub-solar metallicity➔ production of small grains due toshattering is needed for grain growth3-5. Evolution of extinction curves in galaxies
dust amount

grain size distribution

extinction curve

MRN

Asano, Takeuchi, Hirashita, TN+13, MNRAS, 432, 637
Asano, Takeuchi, Hirashita, TN+14, accepted for MNRAS, arXiv/1401.7121‐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
Steep extinction curve is due to thepresence of too much small grains

WNM=0.5
CNM=0.3
MC=0.2

WNM=0.1
MC=0.9Asano, Takeuchi, Hirashita, TN+14

3-7. Summary of dust properties at high z‐Large grains (~0.1 µm) that are supplied by SNe II can produce flat
extinction curves as observed for high-z quasars➔ but, it seems only the contribution from SNe II cannot explaina large amount of dust grains observed for high-z quasars➔ growth of large grains is inefficient‐Shattering + grain growth can produce the dust mass as high as
observed for high-z quasars➔ but, the expected extinction curves are too steep‐The dust model which can explain the dust mass and extinction
curve simultaneously is necessary
If coagulation of dust works very efficiently, it is likely that theextinction curves in both MW and high-z can be explained