The 7th of June, 2017
銀河進化学研究会2017
大阪大学(南部陽一郎ホール)

ダストのサイズ分布を考慮した宇宙論的ダスト形成シミュレーション

青山尚平
Academia Sinica (ASIAA)
Collaborators:
侯冠州(Kuan-Chou Hou)(ASIAA)、清水一紘(大阪大学)、
平下博之(ASIAA)、長峯健太郎(大阪大学)

Introduction: cosmic dust (dust)• Dust consists of heavy elements such as carbon and silicate, floating in theinterstellar medium.
• It is generated in the nucleosynthesis of heavy elements
on stars.
• Dust plays important role in ISM as follows:
http://www.drcom.co.jp/blog/wpcontent/uploads/2013/12/zz3.png
1. Highly efficient catalyst of H2 formation, necessary for starformation.
2. Absorption of the UV light and reemitting in the infrared (IR).
→ The size distribution and abundance of dust grains is essential.

dust
UV lightIR lightIntroduction: previous works
Estimated by extinction

Total duste.g., Spitzer (1978)
Timeline• Hirashita & Kuo(2011)
Grain growth by theaccretion in interstellar
clouds• Asano et al.(2013b, 14)
Entire distribution function
with all ISM processes wasderived.

• Yajima et al.(2015)
Radiation transfer iscalculated with dust.
D∝ZYajima et al (2015) [1411.2626]• Bekki (2015)
Dust is included in anothercomponent of ptcls.
• McKinnon et al. (2016, 17)Dust is included in acomponent of SPH ptcls.

McKinnon et al. (2016)[1505.04792]

We implement detailed dust growth/destruction in ISM into SPH simulation.

Hirashita (2015) 2-component model [MNRAS, 447, 2937]
Hirashita categorizes dusts into two sizes:
large / small dusts( a > 0.03μm , a < 0.03μm ).
a=0.03μmaHirashita’15

In this work, we use
the GADGET3-Osaka SPH code
(Springel ‘05 + modification).

i-th SphL↗

atoms,molecules

grain growthS↗

dust

coagulation

SNe II
SNe IaAGB

Saitoh (2017)

SN shocks
L→×, S→×

M g , Zi ,Ti,ψi etc.

L↘:-(ML/Mg)ψ
S↘:-(MS/Mg)ψ

shattering

Figure credit :Asano

Treatments for collisional processes• Accretion (significant only in dense medium)
TSph < 104 K & nSph > 1 cc-1 : τ = 2 τacc ( 50 K, 103 cc-1)
Hirashita (2015)
Others: τ = ∞ [ No reaction ]Hirashita&Kuo(2011)• Coagulation (significant only in dense medium)
TSph < 104 K & nSph > 1 cc-1 : τ = 2 τcoll(S) ( 50 K, 103 cc-1)
Others: τ = ∞ [ No reaction ]• Shattering (significant only in diffuse gas)nSph < 0.1 cc-1 : τ = τcoll(L)孤立系ならnSph > 0.1 cc-1 : τ = ∞ [ No reaction ]80 pcくらい

Cosmologicalsimulation

50K
103cm-350%

5 ckpcCosmological simulation• L=50 cMpc/h, N=2×2563• Resolution : 9.8 comoving kpc (gravity)
Baryon : ~ 1 comoving kpc• Initial condition is given at z=99 withMUSIC (Hahn & Abel 2011).
• Galaxies are identified with
P-Star groupfinder(Springel+2003; Nagamine+2004).

Dust abundance (space distribution) 50 cMpc Box(0<z<99)

Evolution of surface density ofgas, stars large and small grains
are shown.
Distribution of both of dust grains
is similar to that of gas.
Because of the production anddistribution processes aredifferent between L and S,
the distribution in IGM/ICM isdifferent between large (L) andsmall (S) grains.

Galaxy stellar mass function@ z= 0
Our feedback model can produce
the galaxy stellar mass function
down to M=108.5 M☉Ωdust(z)
全ての星に含まれるダスト観測点銀河に属する• The predicted dust abundance
ガスに含まれるダスト almost agrees with someobservational resultse.g., Menard & Fukugita2012.

銀河間空間に存在するダスト全てのガスに含まれるダスト

Dust mass function @ z= 2.5

The dust mass function wasobservationally reported byDunne+03 .
The predicted mass function
agrees with massive end.
Larger box size is needed toreproduce massive systems.

Dust mass function @ z= 0
The dust mass function wasobservationally bymany authors.

The predicted mass function
agrees with observational data.
Lacking of AGN Feedback,
we overestimate itat the massive end.

z=2.5log10(M*/M☉)

dust-to-gas mass ratio

Dust abundance (Dtot-Z)

Metallicity

The accretion occurs inmassive galaxies as
they form stars.

Dust growth is not
so enhanced
in low mass ones.

Dust abundance (Dtot-Z)
log10(M*/M☉)

dust-to-gas mass ratio

z=0

Metallicity

Our results roughly agree with
Observational results, reported
by Remy-Ruyer et al. (2014) A&A,
563, A31
The difference between
the prediction and observation
might be caused byresolution of simulation.

Dust abundance around massive galaxy.

A surface density of gas, large and small grains at current galaxy are shown.
Simulations with high resolution are required.

Conclusions• We investigate the time evolution and spatial distribution oflarge and small dust grain in an isolated galaxy
based on Hirashita (2015) 2-component dust model using GADGET3-Osakawith sub-grid models for coagulation, shatteringand accretion.
• Our simulation can roughly reproduce observational results such as
total dust abundance Ωdust(z) , Dtot-Z relation and dust/stellar mass function.
• Accretion and coagulation occur in a cosmological simulation andsmall grains whish originate them are important even at z ~ 2 .

• Simulations with larger boxes and high resolutions are required.