2014/02/24

Our recent achievements andongoing works
Takaya Nozawa
Kavli IPMU, Univeristy of Tokyo(➔ moving to the theory group of NAOJ from this April)Contents‐Dust formation in supernovae (and RSG winds)‐Grain growth and formation of HMP stars‐Evolution of grain size distribution in the ISM

1-1. Summary of observed dust mass in CCSNe
SN1987A
Crabtheory
missing cold dust?

Cas A

young SNRs
Gomez+2012

Matsuura+2011
Balow+2010

swept-up IS dust?

young SNeby courtesy of M. Tanaka

Far-IR to sub-mm observations are essential for revealingthe mass of dust grains produced in the ejecta of SNe

1-2. ALMA reveals dust and CO in SN 1987A
SED of 25-years old SN 1987A

Herschel spatialresolution: >10 arcsec

2 arcsec

Indebetouw+2014

detection of COin the ejecta
MCO : >0.01 Msun

ALMA resolves cold (~20 K) dustof ~0.5 Msun (C dust ~ 0.2 Msun)
formed in the ejecta of SN 1987A➔ SNe could be production
factories of dust grains

1-3. Dust formation in Type IIn SN 2010jl
carbonT = 1300 K

MgSiO
3 grains
silicate
T = 1450 K

Dust in SN 2010jl・ dust species: carbon grains

・ grain radius: <0.1μm(possibly <0.01 µm)
・ dust mass: ~10-3 Msun
Maeda, TN, Sahu+2013

1-4. Scaling relation of average grain radius
CMgSiO3

Λon > 30

Λon > 30

TN & Kozasa 2013

Λon = τsat/τcoll : ratio of supersaturation timescale to gas
collision timescale at the onset time (ton) of dust formation

Λon = τsat/τcoll ∝ τcool ngas
・ fcon,∞ and aave,∞ are uniquely determined by Λon・ steady-state nucleation rate is applicable for Λon > 30

1-5. Dust formation in very massive Pop III star
non-rotating stars with >250 Msun
undergo convective dredge-up ofC and O during the RSG phase∝ Mdot0.88

m500vk00

Yoon+2012

TN, Yoon, Maeda, submitted‐1.7 Msun of C grains is produced over the lifetime of the RSG➔ Dust grains formed in the winds are unlikely to be destroyedby the SN shocks because the central star collapses into the BH‐Very massive Pop III RSGs could be sources of carbon grains➔ carbon grains enable the formation of low-mass HMP stars
whose chemical compositions are highly enriched with CNO2-1. Formation conditions of Caffau star
dust mass and composition

thermal evolution of clouds

Schneider+2012‐fragmentation occurs at nH = 1012-1014 cm-3 if fdep > 0.01
➔ if dust formation in SNe is less efficient or strong dust
destruction occur, only M > 8 Msun fragments can form
‐elemental composition, dust formation, fragmentation

2-2. Grain growth in metal-poor gas clouds
growth of Si grains

critical metal abundances

TN, Kozasa, Nomoto 2012

‐grain growth enhances SD in the clouds and enable the gas
fragmentation into sub-solar mass clumps‐for fi,* = 0.5 and 0.001 < fi,0 < 0.1,-4.12 < [Fe/H] < -3.2, -4.6 < [Si/H] < -3.3
ref. [Si/H] = -4.27 for SDSS J102915+2729

2-3. Grain growth and gas fragmentation
growth of MgSiO3 grains

gas fragment condition‐the condition for efficientdust cooling is insensitive
to the initial condensation
factorChiaki, TN, Yoshida 2013

‐critical metalicity Zcrit :~10-5.5 Zsun for r < 0.01 µm

2-4. Application to Caffau star‐growth of multiple grain species with size distribution (SD)‐even if dust formation in the first SNe is inefficient or strong
dust destruction occurs, grain growth during the collapse ofparent gas cloud is sufficiently rapid to activate dust cooling
Chiaki, Schneider, TN+2014, accepted2-5. Towards C-rich HMP stars and Keller starJi, Frebel, Bromm 2014

‐Italy group (Schneider+)- mixing-fallback SNe- formation of C grains➔ formation scenario ofC-rich HMP stars‐Japanese group (Chiaki, TN+)MW dust SD

shock dust SD- more general picture- Nozawa SN-dust model➔ grain growth is not veryimportant‐Keller star with [Fe/H] < -7

Si abundances in HE0107-5240
and HE1327-2326 are so low thatsilicate grains cannot cause thefragmentation of low-mass stars- mixing-fallback SNe- formation of C grains- grain growth- fragmentation## Dust formation in faliled(faint) SNe (Kochanek 2014)

3-1. Flatter extinction curves at high-z

Gallerani+2010

Li+2008
Hirashita, TN+2008‐the extinction curves observed for high-z quasars and GRB
afterglows tend to be flat
‐extinction curve expected from SN dust is flat## average radii of dust grains ejected from SNe are large (~0.1 μm)
because small grains are destroyed by the reverse shocks➔ these seem to support the idea that SNe II are the main dust
sources in the early universe

3-2. Rapid grain growth at high-z objects?
〇 A large amount of dust grains at high-z quasars‐in addition to SN dust (and AGB dust), grain growth is considered
to be needed for explaining such an observed mass of dust
➔ how are extinction curves changed by grain growth?
➔ can grain growth take place efficiently in such an early epoch?

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??

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

shattering

Kuo & Hirashita 2012

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3-4. 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3-5. 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

Asano, TN+2014, in prep

4. Ongoing and future works
・ Dust formation in Supernovae (and RSG winds)‐Dust formation in RSG winds of very massive Pop III stars‐faint (falling-back) SNe, SN 1987A, CO formation …

・ Grain growth and formation of HMP stars‐fragmentation calculations in the Nozawa SN-dust model‐formation scenario of Keller star, 3D calculations

・ Evolution of grain size distribution in the ISM‐Model that self-consistently explain the flat extinction curves
and huge amounts of dust observed for high-z quasars‐Dust evolution in dwarf galaxies, relation of [CII] line at high-z‐ Dust formation in NS-NS (NS-BH) mergers (macronovae)

5-1. Dust formation in Macronovae
condensation efficiency
GRB 130603B

Tanvir+2014

excess of NIR around 7 day

Takami, TN, Ioka 2014 in prep‐processing of optical light byr-process elements‐r-process elements cannot
condense into dust grains‐NS-NS (NS-BH) merger is theformation sites of r-processelements‐formation of C (and Fe)
grains could be possible

5-2. Dust in Macronovae
thermal emission from C grains‐NIR detection of GRB 130603B
around 7 day can be explainedby thermal emission from hot(~1800 K) C grains with themass of ~10-5 Msun
Takami, TN, Ioka 2014 in prep

condensation efficiency of C grains

amount of C atom to achieve
10-5 Msun of C grains‐NS-NS merger (ΔΩ/4π~1)➔ MC = 4x10-3 Msun
‐NS-BH merger (ΔΩ/4π~0.1)➔ MC = 4x10-4 Msun