宇宙磁場を考慮した構造形成シミュレーション

青山尚平(国立天文台)共同研究者 : 嵯峨承平(京都大学)、長峯健太郎(大阪大学)

S. Aoyama et al. in prep.

Cosmological structure formation simulation

with primordial magnetic fields.Shohei Aoyama [NAOJ:ADC]

Collaborators: Shohei Saga (YITP), Kentaro Nagamine (Osaka University)S. Aoyama et al. in prep.

Another project about cosmic dusthas successfully published this fiscal year.

• Recently a couple of observations revealthe star formation rate at z> 10.

• PMFs generate seeds of structures at high-z.→They can (might) reconcile the problems.

Madau (2018)

First galaxy formation at z>10

Mawatari et al. (2019)

Previous work• Inverted collapse (baryon-> cdm)

Radius

Dens

ity

fluct

uatio

n

Shaw & Lewis (2012)

Jeans + damping are considered. Damping scale is appreared.

galacticscale

dampingin the earlyUniverse

線形理論

波数(h Mpc-1)

9/11密度

ゆらぎの分散

緑:磁場なし青:磁場(1nG)の影響

Shaw&Lewis 2012

波数(h Mpc-1)

密度ゆらぎの分散

Formation of baryon density peak by PMF

T. Bringmann et al. (2011)Small scale structure (e.g. galactic scale) has not been constrained tightly.

Galactic scale

Simulation setup• Initial condition CAMB [Lewis&Challinor 2012 modified by S. Saga]

(see. Shaw & Lewis 2012)& MUSIC [Hahn&Abel 2011] & Planck cosmology(2015)

• GADGET3-Osaka (Springel 2005) + cooling package (grackle [B. Smith 2016])

• PMFs (B1Mpc = 0.2 nGauss; nB=-2.9) is implemented as an initial density bump of baryon. (cf. T. Minoda et al. 2019)

• L=10 Mpc/h; N=10243• The resolution is determined for resolving Jeans mass at redshift 40.• The effects of PMFs are implemented only in the initial condition.

Simulation cost

•Rank B+ 1024 core + 3 months

•They runs smoothly.

Matter power spectrum P(k) at z=40 with PMFs (0.2 n Gauss)

Effect of PMFs

cf. P(k) w/o PMF

The success of initial conditions

• Implementation of attenuation effects of baryons.

• Cutoff is successfully realized.

wavenumber k

Bary

onic

mat

ter p

ower

P(k

)

shot noise level

Mass function of the galaxies

• The density is very high (～3 Mpc-1).

• The mass is determined by the bump scale.

The success of initial conditions

wavenumber k

Bary

onic

mat

ter p

ower

P(k

)

galaxies

H2 cooling at z≳50 (see. Fig. 1 in Tegmark+1997)

Star formation recipe & SED

• Density and temperature criterion : n > 1 cm-3 & Tgas < 104 K

• Line cooling of hydrogen atom is dominated in high temperature (T>104K) and molecular hydrogen cooling is dominated (T

Spectral energy density

Almost identical SEDs are obtained.

Spectral energy density

1/200 JWST

JWST might detect such a galaxy when it is magnified by gravitational lens.

Star formation history

Redshift z

ρ UV

[erg

/s/H

z]@

1500

Å

Mawatari+19

We overpredict the SFRD (ρUV) even B1Mpc = 0.2 nGauss.

How are they observed in realistic observations?

• z=9 Our first galaxies can be responsible for z=9.1 galaxy (Hashimoto et al. 2018a)

• z=6~7 galaxies (old populations might exist.)

• Reionization (we have to calculate radiation transfer for it.)

Conclusion

• We reproduce the density perturbation with PMFs.

• Because PMFs assemble the baryons, existence of the galaxies with PMFs are suggested.

• Our model slightly overestimates SFRD although we set B1Mpc = 0.2 nGauss .

宇宙磁場を考慮した�構造形成シミュレーションCosmological structure formation simulation�with primordial magnetic fields.Another project about cosmic dust�has successfully published this fiscal year.First galaxy formation at z>10Previous workShaw & Lewis (2012)線形理論スライド番号 8Simulation setupSimulation costMatter power spectrum P(k) at z=40 with PMFs �(0.2 n Gauss)The success of initial conditionsMass function of the galaxies at redshift 40The success of initial conditionsStar formation recipe & SEDSpectral energy density at redshift 40Spectral energy densityStar formation historyHow are they observed in realistic observations?Conclusion