Magnetic Activity in the Galactic
Centre Region
Suzuki, T. K.
Arts & Sciences, U.Tokyo

Dec. 22nd, 2017
Suzuki, Fukui, Torii, Machida, & Matsumoto 2015 MNRAS, 454, 3049
Kakiuchi, Suzuki, Fukui, Torii, Machida, & Matsumoto 2017 (arxiv:171204209)
Suzuki & Lazarian 2017 (arxiv:171003930)
Thanks to PC clusters(Ta lab.), Cray XC30 (NAOJ), HITACHI SR16000(Yukawa inst.)

Outline
Roles of Magnetic Field in the Galactic CentreRegion (10 pc ∼ 1 kpc) on Complex Flows• Radial Flows–Parallelogram in an l − 3 diagram• Outflows–Relation to the Fermi Bubbles?

Galactic l–3 diagram

Galactic l–3 diagram

CO(J=1-0) Dame+ 2001

(Rodriguez-Fernandez & Combes 2008)

Galactic l–3 diagram

CO(J=1-0) Dame+ 2001

(Rodriguez-Fernandez & Combes 2008)

12 CO(J=1-0) by NANTEN
Torii+ 2010

Galactic l–3 diagram

CO(J=1-0) Dame+ 2001

(Rodriguez-Fernandez & Combes 2008)

12 CO(J=1-0) by NANTEN
Torii+ 2010

asymmetric “Parallelogram”
in the l–3 diagram

Galactic l–3 diagram

CO(J=1-0) Dame+ 2001

(Rodriguez-Fernandez & Combes 2008)

c.f. Circular motion-2Column Density (|z|<0.2kpc, n > 1 cm-3) at t=0(Myr)x(kpc) at y=0-1-0.5
00.512100

100

100
1-100

Column Density (1021cm-2)

Velocity (km s-1)

200-2000.1
151050l (deg)-5-10-15

12 CO(J=1-0) by NANTEN
Torii+ 2010

asymmetric “Parallelogram”
in the l–3 diagram

Galactic l–3 diagram

CO(J=1-0) Dame+ 2001

(Rodriguez-Fernandez & Combes 2008)

c.f. Circular motion-2

Column Density (|z|<0.2kpc, n > 1 cm-3) at t=0(Myr)x(kpc) at y=0-1-0.500.5121001001001-100

Column Density (1021cm-2)

Velocity (km s-1)

200-2000.1
151050l (deg)-5-10-15

12 CO(J=1-0) by NANTEN
Torii+ 2010

asymmetric “Parallelogram”
in the l–3 diagram⇒ Non-circular motionBar⇔ Non-circular Motion?

Bar⇔ Non-circular Motion?

Artistic view (NASA JPL)

Stellar Bar⇐IR obs.
Okuda+ 1977; Hayakawa+ 1981;
Matsumoto+ 1982;
Blitz & Spergel 1991; Churchwell+2009

Bar⇔ Non-circular Motion?

Binney+ 1991
Artistic view (NASA JPL)

Stellar Bar⇐IR obs.
Okuda+ 1977; Hayakawa+ 1981;
Matsumoto+ 1982;
Blitz & Spergel 1991; Churchwell+2009

Bar⇔ Non-circular Motion?

Binney+ 1991
Artistic view (NASA JPL)

Stellar Bar⇐IR obs.
Okuda+ 1977; Hayakawa+ 1981;
Matsumoto+ 1982;
Blitz & Spergel 1991; Churchwell+
2009

Observe a bar from an oblique angle

Bar⇔ Non-circular Motion?

Binney+ 1991
Artistic view (NASA JPL)

Stellar Bar⇐IR obs.
Okuda+ 1977; Hayakawa+ 1981;
Matsumoto+ 1982;
Blitz & Spergel 1991; Churchwell+
2009

Observe a bar from an oblique angle⇒ symmetric Parallelogram

Bar⇔ Non-circular Motion?

Binney+ 1991
Artistic view (NASA JPL)

Stellar Bar⇐IR obs.

Observe a bar from an oblique angle⇒ symmetric Parallelogram

Okuda+ 1977; Hayakawa+ 1981; Many works with a bar potential
Matsumoto+ 1982;
Blitz & Spergel 1991; Churchwell+ Koda & Wada 2002; Baba+ 2010; Molinari+ 2011; Shin & Kim
2009 2015

Magnetic Fields

Nishiyama+ 2010

Chuss+ 2003

– inferred B fields– from IR pol. by IRSF

from FIR/sub-mm polariztion

Caveat: AV ≈ 3 mag.

Magnetic Field –contd.

Pillai+ 2015B ∼ 5 mG
Assuming√
δB/ ρ ≈ δ3(Chandrasekhar & Fermi method)

Magnetic Loops

Magnetic Loops

Fukui+ 2006

Magnetic Loops

Machida+ 2009

Fukui+ 2006

Magnetic Loops

Machida+ 2009

Parker Instability (Mag. Buoyancy)

Parker 1966

Fukui+ 2006

Magnetic Loops

Machida+ 2009

Parker Instability (Mag. Buoyancy)

Parker 1966

Fukui+ 2006

B field ⇒ Dynamics

Magnetic Field at Galactic Centre• > 50 µG Crocker+ 2010

if B is smaller, synchrotron loss is suppressed⇒ Overproduce γ–rays by inverse Compton > EGRET(300MeV)• Complex structure e.g. filaments ∼ mG (?)
Yusef-Zadeh+ 1984; Tsuboi+ 1986; Chuss+ 2003; Oka+ 2005;
Nishiyama+ 2010; .....

• ∼ 5 mG in an IR dark cloud Pillai+ 2015
via Chandrasekhar-Fermi method

Magnetic Field at Galactic Centre• > 50 µG Crocker+ 2010

if B is smaller, synchrotron loss is suppressed⇒ Overproduce γ–rays by inverse Compton > EGRET(300MeV)• Complex structure e.g. filaments ∼ mG (?)
Yusef-Zadeh+ 1984; Tsuboi+ 1986; Chuss+ 2003; Oka+ 2005;
Nishiyama+ 2010; .....

• ∼ 5 mG in an IR dark cloud Pillai+ 2015
via Chandrasekhar-Fermi method

Comparison of Pressure• Molecular Clouds: ())(nTPg ∼ 10−10 erg/cm3 104 cm−3100K• Turbulence:() ( δ3 )2Pturb ∼ 10−9 erg/cm3 3 n −3 10km/s• Mag.Field: P B10 cm(∼ 4 × 10−10 erg/cm3)

2
B100µGAim of This Work

Aim of This Work
Magnetic Activity⇒Non-Circular & Vertical Flows?
by MHD simulations.

Aim of This Work
Magnetic Activity⇒Non-Circular & Vertical Flows?
by MHD simulations.
• Axisymmetric potential(Miyamoto & Nagai 1975)

Φ(R, z) =∑3i=1√−GMi√
R2 +(ai + b2 +z2 )2i

SMBH 1
Bulge 2
Disk 3

Mi (1010 M⊙ )4.4 × 10−4
2.05
25.47

ai (kpc)
007.258

bi (kpc)
00.4950.52

Aim of This Work
Magnetic Activity⇒Non-Circular & Vertical Flows?
by MHD simulations.
• Axisymmetric potential(Miyamoto & Nagai 1975)

Φ(R, z) =

∑3
i=1

√−GMi
√
R2 +(ai + b2 +z2 )2i

SMBH 1
Bulge 2
Disk 3

Mi (1010 M⊙ )4.4 × 10−4
2.05
25.47

ai (kpc)
00
7.258

bi (kpc)
00.4950.52• Study the gas dynamics under the fixed grav.

potential.

MHD Simulation –Setup–φrθ(Suzuki & Inutsuka 2009; 2014 for Protoplanetaray Disks)• Simulation Region (3D Spherical Coordinates):(r, θ, ϕ) = (0.01 − 60 kpc, ±π/3, 2π) (full rot.)
resolved by (384,128,256)• Ideal MHD Equations (Newtonian)∂ρ
Mass consv.: ∂t + ∇ · (ρ3) = 02( B·∇) BMom. consv.: ddt3 + ρ1 ∇(p + B) − 4πρ + ∇Φ = 08π
Eng. consv.: ρ de= −p∇ · 3dt

B evol.: ∂∂tB = ∇ × (3 × B) with ∇ · B = 0• Locally Isothermal)(R −1• Initial Mag. field: B z = 0.71µG 1 kpc
in R > 35 pc

Overview

2kpc-long

2kpc-short

1kpc-long

1kpc-short

0.6kpc-shortAmplification of Magnetic Field

CenterMassGravity

Magneto-Rotational
Instability(Velikhov 1959; Chandrasekhar 1961;
Balbus & Hawley 1991)

Parker Instability(Magnetic Buoyancy)

Bφ Generation
by DifferentialRotation(Parker 1966)

Stratified MRI

Local MRI

Evolution of B

Average B• 400-500µG
at 0.1 kpc• 200µG
at 0.5 kpc

ϕ (azimuthal) & z (vertical) averaged

Face-on View (@Galactic Plane)l–3 diagram near GC(Only NH > 100 cm−3 used to derive Column density)l–3 diagram near GC(Only NH > 100 cm−3 used to derive Column density)

Time-dependent Parallelograml–3 diagram: Observation – Simulationl–3 diagram: Observation – Simulation-3

Column Density (|z|<0.2kpc, n > 100 cm ) at t=401.0(Myr)x(kpc) at y=0-0.5
-0.25
00.25
0.5

100Velocity (km s-1)

200
100

100-100

1Column Density (1021cm-2)

300

-200
-300

0.1
43210l (deg)-1-2-3-4l–3 diagram: Observation – Simulation-3Column Density (|z|<0.2kpc, n > 100 cm ) at t=401.0(Myr)x(kpc) at y=0-0.5
-0.25
00.25
0.5

100Velocity (km s-1)

200
100

100-100

1Column Density (1021cm-2)

300-200
-300

0.1
432

10-1-2-3-4l (deg)

NANTEN Obs. Torii+ 2010
Need N(H2 )/I(CO)(≈ 2.3 × 1020 cm−2 (K km s−1 )−1 )(Strong+ 1988)
for direct comparison

l–3 diagram: B-field vs. Bar Potential

Column Density (|z|<0.2kpc, n > 100 cm-3) at t=401.0(Myr)x(kpc) at y=0-0.5-0.25
00.25
0.5

100Velocity (km s-1)

200
100100-1001

Column Density (1021cm-2)

300-200-300

0.143210l (deg)-1-2-3

Our Result-4

NANTEN Obs. Torii+ 2010

l–3 diagram: B-field vs. Bar Potential

Column Density (|z|<0.2kpc, n > 100 cm-3) at t=401.0(Myr)x(kpc) at y=0-0.5-0.25
00.25
0.5

100Velocity (km s-1)

200
100

100-1001Column Density (1021cm-2)

300-200-3000.143210l (deg)-1-2-3

Our Result-4

NANTEN Obs. Torii+ 2010

with Bar Potential & Hydro (Rodriguez-Fernandez & Combes 2008)

Excitation of Non-circular MotionΩ1Ω2 Ω
3Ω1 > Ω2 = Ω3

Amplification of Magnetic Field

Amplification of Magnetic Field• Growth Rate of MRIωMRI,maxCenterΩ=

1 ∂ ln Ω
2 ∂ ln R

ωMRI,max for most unstable mode

MagnetoRotational
Instability

Amplification of Magnetic Field• Growth Rate of MRIωMRI,maxΩCenter=1 ∂ ln Ω
2 ∂ ln R

ωMRI,max for most unstable mode

• Winding by Dif.Rot.
MagnetoRotational
Instability∂B= ∇ × (3 × B)
∂t
1 ∂Bϕ

⇒

Bφ Generation
by Differential
RotationΩ ∂t= BR∂ ln Ω∂ ln R

Amplification of Magnetic Field• Growth Rate of MRIωMRI,maxΩCenter=1 ∂ ln Ω
2 ∂ ln R

ωMRI,max for most unstable mode

• Winding by Dif.Rot.
MagnetoRotational
Instability∂B= ∇ × (3 × B)
∂t
1 ∂Bϕ

⇒

Bφ Generation
by Differential
RotationΩ ∂t= BR∂ ln Ω∂ ln RΩ
Strong Dif.Rot. (large ∂∂ ln)
ln R⇒ Fast Amplification of B
• Strong B field• Efficient Transport ofAngular Momentum (large α)

Excitation of Non-circular MotionΩ1Ω2 Ω3Ω1 > Ω2 = Ω3

Excitation of Non-circular Motion

BαΜ,1αM,2αM,3αM,2 > αM,1,αM,3Excitation of Non-circular Motion
B

Ω1

Ω2 Ω3
Ω1
Ω2

Excitation of Non-circular Motion
B

Ω1

Ω2 Ω3
Ω1
Ω2

Outflows
1/β-1v = 200 km s0.8

1

0.6
0.4

0.1

z (kpc)

0.2
00.01
-0.2
-0.4
0.001
-0.6
-0.8
00.2

0.4
0.6
R (kpc)0.8

1Outflows1/β-1

v = 200 km s

0.810.6• Mass outflow rate:

0.4

0.1

z (kpc)

0.2
00.01
-0.2
-0.4
0.001
-0.6
-0.8
00.2

0.4
0.6
R (kpc)0.81

Ṁ ≈ 70M⊙ /yrOutflows
1/β-1v = 200 km s

0.8

10.6

• Mass outflow rate:

0.4

0.1

z (kpc)0.2

Ṁ ≈ 70M⊙ /yr• Kinetic Luminosity:

01
Ṁ3 ≈2( 3 )2
erg/s
1041 50km/s
0.001≈ 3 × 1048 erg/yr
0.01

-0.2
-0.4
-0.6
-0.8
00.2

0.4
0.6
R (kpc)0.8

1Fermi Bubble

Fermi Bubble• Energetics from X-ray obs

n ∼ 10−2 cm−3 , kT ∼ 2keV, l ∼ 10kpc⇒ E ∼ 1054−55 erg

Fermi Bubble• Energetics from X-ray obs

n ∼ 10−2 cm−3 , kT ∼ 2keV, l ∼ 10kpc⇒ E ∼ 1054−55 erg• Required 3 ∼ 102−3 km/s ⇒ τ ∼ 107 yr

Fermi Bubble• Energetics from X-ray obs

n ∼ 10−2 cm−3 , kT ∼ 2keV, l ∼ 10kpc⇒ E ∼ 1054−55 erg• Required 3 ∼ 102−3 km/s ⇒ τ ∼ 107 yr
Required Input E/τ ∼ 1048 erg/yr

Magnetic Activity – Fermi Bubble ???

Magnetic Activity – Fermi Bubble ???
• Outflow in Simulation: ≈ 3 × 1048 erg/yr

Magnetic Activity – Fermi Bubble ???
• Outflow in Simulation: ≈ 3 × 1048 erg/yr• Required Input for Fermi Bubble: ∼ 1048 erg/yr

Magnetic Activity – Fermi Bubble ???
• Outflow in Simulation: ≈ 3 × 1048 erg/yr• Required Input for Fermi Bubble: ∼ 1048 erg/yr

Alfvén wave emission

Magnetic Activity – Fermi Bubble ???
• Outflow in Simulation: ≈ 3 × 1048 erg/yr• Required Input for Fermi Bubble: ∼ 1048 erg/yr

Alfvén wave emission

LA ≈ 2πl2 δB
38π A≈ 3 × 1048 erg/yr( δB )2 () ( n )−1/2
B× 10µG 100µG 10−2 cm−3( l )221kpc

Magnetic Activity – Fermi Bubble ???
• Outflow in Simulation: ≈ 3 × 1048 erg/yr• Required Input for Fermi Bubble: ∼ 1048 erg/yr

Alfvén wave emission

LA ≈ 2πl2 δB
38π A≈ 3 × 1048 erg/yr( δB )2 () ( n )−1/2
B× 10µG 100µG 10−2 cm−3( l )221kpc→ dissipation in pre-existing
MHD turbulence
Lazarian (2016)

Upward Poynting Fluxz– LA (“Alfvénic” Luminosity)
inside 1 kpc

LA ∼ 1040 − 1041 erg s−1∼ 1048 erg yr−1

ModelInject Poynting flux fromthe top of the Bulge.
2 Solve Propagation &Dissipation1Formulation
Hydro + Poynting Fluxdρdt+ρ ∂A ∂z( A3 z ) = 0.

(1)

∂∂Φ
( pg + pA ) − ρ= 0,(2)dt∂z∂zdeg pg ∂ρ+( A3 z ) = HA(3)A ∂zdt()][3z ∂dẽA 1 ∂1ρ+AρẽA 3A + 3 z −(ρẽA ) = −γA ρẽA ,22 ∂zdt A ∂z
ρd3 z=−(4)

B2
⊥

B2
⊥

where eA ≡ 21 32⊥ + 8π = 32⊥ = 4π .

Poynting Flux-driven Outflow

Poynting Flux-driven Outflow

at 10 kpc
• T ≈ 6 × 106 K• 3 ≈ 400 − 500 km s−1• n ≈ (6 − 7) × 10−4 cm−3

⇔ Observation(Miller & Bregman 2016)

SummarySummary
Global MHD simulation for Bulge + Disk
under Axisymmetric Grav. Pot.
Magnetic Activity ⇒Summary
Global MHD simulation for Bulge + Disk
under Axisymmetric Grav. Pot.
Magnetic Activity ⇒• Non-circular Motion

Summary
Global MHD simulation for Bulge + Disk
under Axisymmetric Grav. Pot.
Magnetic Activity ⇒• Non-circular Motion• Time-dependent “parallelogram” in l–3
diagram by Radial Motion

Summary
Global MHD simulation for Bulge + Disk
under Axisymmetric Grav. Pot.
Magnetic Activity ⇒• Non-circular Motion• Time-dependent “parallelogram” in l–3
diagram by Radial Motion• High 3 feature by Vertical Motion⇐ Magnetic sliding slope via Parker Instability

Summary
Global MHD simulation for Bulge + Disk
under Axisymmetric Grav. Pot.
Magnetic Activity ⇒• Non-circular Motion• Time-dependent “parallelogram” in l–3
diagram by Radial Motion• High 3 feature by Vertical Motion⇐ Magnetic sliding slope via Parker Instability• Large-scale Outflows

Summary
Global MHD simulation for Bulge + Disk
under Axisymmetric Grav. Pot.
Magnetic Activity ⇒• Non-circular Motion• Time-dependent “parallelogram” in l–3
diagram by Radial Motion• High 3 feature by Vertical Motion⇐ Magnetic sliding slope via Parker Instability• Large-scale Outflows
Future Extensions• Realistic Heating/Cooling• Detailed trajectories of gas clouds
Kruijssen+ 2015; Henshaw+ 2016