First star discrimination in the metalabundance of the z=3 intergalactic medium(赤方偏移3の銀河間物質における初代星由来の重元素汚染)

Takanobu Kirihara (Chiba University)
Collaborators

Kenji Hasegawa (Nagoya Univ.), Masayuki Umemura (Tsukuba Univ.),
Masao Mori (Tsukuba Univ.), Tomoaki Ishiyama (Chiba Univ.)

Extremely metal-poor star

Pop. III search

Direct observation of SN at high-z
WFIRSTJWSTWhalen +18

Frebel & Norris 2015see also TK+19

Distribution of low-mass
pop. III stars in the MW

Ishiyama+16

Frebel & Norris 2015
Low-z IGMで探す

21 cm signal

Bowman+18

Extremely metal-poor star

Pop. III search

Direct observation of SN at high-z
WFIRSTJWSTOur Galaxy

Frebel & Norris 2015see also TK+19

High-z (z≳10)

Whalen +18

21 cm signal

Metal abundance of low-z IGM

Distribution of low-mass
pop. III stars in the MW

Ishiyama+16

Frebel & Norris 2015
Low-z IGMで探す(z=3)

Bowman+18

Population III star formation

Susa+14z=14Pop. III stars
 formed in pristine gas H2 cooling typically very massive SN explosions at high-z(e.g., Tegmark +97; Omukai & Nishi +98; Nakamura & Umemura +01;
Abel+02; Bromm+02; Hosokawa +11; Stacy+12)
59 clouds

1540 cloulds

Hirano+15

Susa+14

Hirano+154

IGM metal observations
Metallicity of IGM @z=3
19 QSO spectrum A universal metallicity floor?
Z=10−3 Z☉ at z～3 (Songaila 1997)

 Can Pop. III stars explain the floor?
(e.g., Yoshida+04)

 No such floor at z～3 (Simcoe+04)

 Roughly 30% of lines in the Lyα forest
in QSO spectrum are [C, O/H]<−3.5(Simcoe+04)
Schaye +03

 ～40% of HI lines with 14.0< log NHI<14.8 show an associated CIV
absorption.
(D’Odorico +16)

We investigate where heavy elements originating from Pop. III stars dominate
5
in the cosmic volume using cosmological simulations.

Cosmological simulation + Pop. III model
N-body simulation(Ishiyama +16)
+ Pop. III formation model

N=20483

Boxsize: 8 ℎ−1 cMpc

Minimum halo mass: 2.4× 105
z=3

Metal injection(a) PISN yield (200)(b) reduced SFRD by 90%(c) CCSN yield(30)(d) reduced SFRD by 90%

Model (a)Thickness of slice: 160 pkpcSpatial distribution of metals
Model (a)Galactic metal: Illustris-1 simulation(Vogelsberger+14)
AREPO (moving-mesh)
75 cMpc/h box
coarse-grained to 5123

Thickness of slice: 160 pkpc

Metal density distributionPISN𝜌𝜌𝑍𝑍 originated in Pop. III
SN is a dominant
contributor inlog(1 + δcell)<1.8(Model (a))
log(1+δcell )< 1.3(Model (b) and (c))
log(1+δcell )< 1.1(Model (d))

CCSN

Volume fraction is large
at lower density region
cellsize～50 kpc

0 < log(1 + δcell) <1.8
:15 % of the whole volume

Pop. III metal dominated region
The colored region is dominatedby Pop. III originated metals.

PISNCCSN

Volume fraction of the metal enriched region
If observations reach 𝜌𝜌𝑍𝑍 > 10−34 g cm−3 ,the volume fraction of Pop. III metals
dominated region is 0.32 in Model (a).
As for Models (b): 0.11(c): 0.08(d) 0.0017

PISNCCSN

cellsize～50 kpc

The average number of cells:
Model (a): 18
Model (b): 5.8
Model (c): 4.4
Model (d): 0.093
in the line-of-sight with ∆z = 0.012 at z = 3per QSO spectrum.

Elemental abundance pattern

The yield table is provided by Nomoto+13.

 Abundance ratios between C, N and O are useful to distinguish the origin.
 If PISN-originated metal is dominated, the gas would be Si-rich and S-rich even in
the contaminated cases.

Summary• We investigated the Pop. III metal distribution in the cosmologicalvolume at z=3• We compare the distribution of metals with galactic originated metals(Illustris-1 simulation)• Pop. III metals have substantial enhancement at lower-density regions
0<log(1+δcell)<1.3• The median value of the volume averaged metallicity is Z～10−4.5~−2 Z☉• Relics of Pop. III stars should be discriminated by absorption lines in theQSO spectrum that have passed through a lower-density region