Nature of Dustin the early universe
Takaya Nozawa
IPMU (Institute for the Physics and Mathematicsof the Universe, Univ. of Tokyo)

Collaborators
T. Kozasa, A. Habe (Hokkaido Univ.), Eli Dwek（NASA）
H. Umeda（Univ. of Tokyo）, N. Tominaga（NAOJ）
K. Maeda（IPMU）, K. Nomoto（IPMU/Univ. of Tokyo)

Contents
1. Introduction
2. Dust formation in primordial SNe
3. Dust evolution in primordial SNRs
4. Extinction curve expected at high-z2

1-1. A large amount of dust at z > 5・ The presence of large amounts of dust grains with mass of>10^8 Msun has been confirmed for ~30% of z > 5 quasars(Bertoldi et al. 2003; Priddey et al. 2003; Robson et al. 2004;
Beelen et al. 2006; Wang et al. 2008a, 2008b)
SDSS J1148+5251 at z=6.4
LIR>10^13 Lsun
180 K, β=040 K, β=2a rapid enrichment with dust
formed in the ejecta of SNe
0.1-1 Msun of dust per SN isrequired to form to explain alarge content of dust at high-z
galaxies

Robson et al. (2004, MNRAS, 351, L29)

(Morgan & Edmunds 2003,Maiolino et al. 2006;
Dwek et al. 2007)

1-2. Extinction curves at high-z
Broad absorption line (BAL) quasars at low-z➔ reddened by dust
SDSS J1048+4637 at z=6.2
GRB 050904 at z=6.3

Maiolino et al. (2004, Nature, 431, 533)

Stratta et al. (2007, ApJ, 661, L9)

Source and evolution of dust at high redshift (z > 5)
are different from those at low redshift (z < 4)

1-3. Role of dust in the early universe
・ Dust has great impacts on the formation processes of stars－ forming molecules (mainly H2) on the surface－ providing additional cooling pathways of gas throughthermal emission (e.g., Omukai et al. 2005, Schneider et al. 2006)
・ Dust absorbs stellar light and re-emits it by thermal radiation➔ plays a crucial role in interpreting the SFR and the IMFof the early generation of stars from observations

It is essential to clarify the properties ofdust in the early epoch of the universe!
We aim at revealing the composition and size,amount of dust by treating self-consistently theformation and destruction processes of dust

2. Dust Formation in primordial SNe
at ~1 days
He-coreH-envelope

NS or BH
He–layer (C>O)
O–Ne-Mg layer
Dust formation
Si–Slayeryears
at ~1-3
after explosion
Fe–Ni layer

2-1. Calculations of dust formation○ nucleation and grain growth theory(Kozasa & Hasegawa 1987)○ models of Pop III SNe (Umeda & Nomoto 2002)－ SNe II ： Mpr = 13, 20, 25, 30 Msun (E51=1)－ PISNe ： Mpr = 170 Msun (E51=20), 200 Msun (E51=28)○ formation of CO and SiO molecules ➔ complete○ time evolution of gas temperature－ derived by the radiative transport calculations taking
account of energy deposition from 56Ni and 56Co
○ mixing of elements within the He-core－ unmixed case (onion-like composition)－ uniformly mixed case (retaining the density profile)2-2. Dust formed in the unmixed ejecta

・ In the unmixed ejecta, various dust species form, reflecting
the difference of elemental composition in each layer

・ C, SiO2, and Fe grains have lognormal-like size distribution,
while the other grains have power-law-like size distribution

2-3. Total mass of dust formed(Nozawa et al. 2003, ApJ, 598, 785)
SNe II・ Total dust mass increases with increasing progenitor mass
SNe II ： Mdust = 0.1-2 Msun, fdep = Mdust / Mmetal = 0.2-0.3
PISNe ： Mdust = 10-60 Msun, fdep = Mdust / Mmetal = 0.4-0.5

3. Dust Evolution in Primordial SNRs
T = (1-2) x104 K
nH = 0.1-1 cm-3

He coreFSRSCD

3-1. Calculation of dust destruction○ SN ejecta models (Umeda & Nomoto 2002)
・ SNe II : Mpr=13, 20, 25, 30 Msun (E51=1)
・ PISNe : Mpr=170 (E51=20), 200 Msun (E51=28)○ The ambient medium (homogenious)
・ gas temperature ; T = 104 K・ gas density ; nH,0 = 0.1, 1, and 10 cm-3

○ Dust (test particle)
・ deceleration by the gas drag, erosion by sputtering← initial size distribution and spatial distribution of dust
The calculation is performed from 10 yr up to ~106 yr

3-2.Temperature and density of gas
Model : Mpr=20 Msun (E51=1)
nH,0 = 1 cm-3
Downward-pointing arrows:
forward shock in upper panel
reverse shock in lower panel

The temperature of the gas
swept up by the shocks➔ 106-108 K↓
Dust grains residing in this hot
gas are eroded by sputtering3-3. Evolution of dust in SNRs
Model : Mpr=20 Msun (E51=1)
nH,0 = 1 cm-3
Dust grains in the He core collidewith reverse shock at (3-13)x103 yr

The evolution of dust heavily
depends on the initial radiusand composition(Nozawa et al. 2007, ApJ, 666, 955)

aini = 0.01 μm (dotted lines)➔ completely destroyedaini = 0.1 μm (solid lines)➔ trapped in the shellaini = 1 μm (dashed lines)➔ injected into the ISM

3-4. Size distribution of surviving dust

The size distribution of surviving dust is greatly deficient insmall-sized grains, compared with that at its formation➔ Dust grains in the early universe are dominated by largesized grains of > 0.01 μm

3-5. Total mass of surviving dust
~70%
~30%
~10%

Total mass of dust surviving the destruction for Type II SNRs;
0.01-0.8 Msun for SNe II (nH,0 = 0.1-1 cm-3)
0.001-15 Msun for PISNe (nH,0 = 0.1 cm-3)➔ high enough to explain dust content in high-z galaxies(Morgan & Edmunds 2003, Maiolino et al. 2006; Dwek et al. 2007)

4. Extinction curve expected at high-z
・ Evolution of dust within SNRs
➔ small-sized grains are destroyed more efficiently➔ for the higher ambient gas density, the averageradius of surviving dust shifts toward larger size・ 2 π a / λ > 1 ➔ Qext ~ const

4-1. Flattened extinction curves

flat extinction curve at high redshifts !

Hirashita et al. (2008, 384, 1725, MNRAS)

4-2. Extinction in high-z BAL quasars

Priddey et al. (2003, MNRAS, 344, L74)

Maiolino et al. (2004, A&A, 420, 889)

4-3. Extinction curves of low-z AGNs
coagulation of grains?
sublimation of small grains?
(Maiolino et al. 2001)

Gaskell et al.
(2004, ApJ, 616, 147)

Willot (2005, ApJ, 627, L201 )Gaskell & Benker (2008, astro-ph/0711.1013)

4-4. Extinction curves from GRBs
GRB 020405 at z=0.69

Stratta et al. (2005, A&A, 441, 83)

coagulation of grains in dense clouds
evaporation of small grains by GRB
destruction of small grains by shock
Li et al. (2008, ApJ, 678, 1136)

Summary・ The fates of dust grains within SN remnants dependon their initial radii and compositions
・ The size distribution of dust surviving the destruction
is weighted to relatively large size (> 0.01 μm)

・ The mass of surviving dust decreases with increasing
the ambient gas density (and explosion energy of SNe)for nH,0 = 0.1-1 cm-3
SNe II ➔ Mdust = 0.1-0.8 Msun
PISNe ➔ Mdust = 0.1-15 Msun
・ Extinction curves in the early universe are expected tobe flat.