Kensuke Kakiuchi (Nagoya Univ./ The Univ. of Tokyo) Collaborators: - PowerPoint PPT Presentation

Dec.22, 2017 @Kagoshima Univ. Kensuke Kakiuchi (Nagoya Univ./ The Univ. of Tokyo) Collaborators: Takeru K. Suzuki (The Univ. of Tokyo/ Nagoya Univ.), Yasuo Fukui(Nagoya Univ.), Kazufumi Torii(NRO), Mami Machida(Kyusyu Univ.), Ryoji Matsumoto (Chiba Univ.) Kakiuchi et al. In prep. (ArXiv:1712.04209)

Outline  The Galactic Center (GC) region  Vertical structure Simulated l-v diagram in MHD simulation data Column density (10 21 cm -2 ) 300 100 LoS velocity (km s -1 ) 200  Rising loops and 10 100 0 fast downflows 1 -100 -200 0.1 -300 4 2 0 -2 -4 Galactic longitude (degree)

The galactic center (GC) region : Within a few parsec region 200pc 8.0kpc Galactic 銀河面 plane Sgr A Radio continuum (330MHz; LaRosa et al. 2000 ) The Sun Super massive BH Sgr A*, massive star cluster, SNR ✓ ✓ 5-10 % of total molecular gas in the Milky Way collected. Molecular gas: High density, High temperature ✓

Velocity structure in the GC region - 12 CO(1-0) map NANTEN (Torii+10) - Color : column density N(H2)/I(CO) ≒ 2.3 x 10 20 cm -2 (K km s -1 ) -1 ) Only circular motion 300 Line of sight velocity [km/s] Distance from GC (kpc) 10 250 10 200 200 LOS vel. [km/s] 200 9 150 8 100 100 100 7 50 6 5 0 0 5 0 -50 4 -100 -100 3 -150 2 -100 -200 -200 1 0 -250 0 -200 0 5 -5 Galactic longitude[degree] 5 0 -5 Galactic longitude [degree] Complex structure Non-circular motion

Bar potential → Non-circular motion ? ❖ Orbital calculation (Binney+1991) - Bar-like stellar gravitational potential (detected near 3kpc) → gas motion in the GC region ? - As a result, the gas is excited radial motion on bar potential - However, complex features cannot is reproduced, even if 3D simulation ( Rodriguez-Fernandez & Combes 2008 ). A B 300 Line of sight velocity [km/s] 200 LoS velocity [km s -1 ] 200 0.5 100 100 Y [kpc] 0 0 0 B -100 -100 -0.5 A -200 -200 -0.2 0 0.2 4 2 0 -2 -4 4 2 0 -2 -4 5 0 -5 X [kpc] Galactic longitude [deg] Galactic longitude [degree]

Bar potential v.s. Magnetic Field ! ❖ Polarization observation (Chuss+2003, Nishiyama+ 2010) ✓ Detection of vertical field and pallarel field (Disccusion: non-thermal filament structure) ❖ Large magnetic field strength ( ※ typical strength is 1μG @ molecular cloud in disk region ) ✓ globally > 50μG ( Crocker + 2010 ) ✓ Locally ~ 0.1-1mG ( Yuzef-Zadeh+1984 ) ✓ Inner the dark cloud 2-5 mG ( Pilai et al. 2015 ) The loop structure of molecular cloud ❖ (Fukui+06, Machida+09, Torii+10a,b) It has potential that it is sign of Parker Instability. ✓

Vertical Structure 12 CO(1-0) map NANTEN (Torii+10) 4 Galactic latitude 2 0 -2 -4 5 0 -5 Galactic longitude - Vertical motion can play important roles c.f. The Galactic center radio lobe (GCL; Sofue & Handa 1984) Double helix structure (Enokiya+2014)

Parker Instability Parker (1966,1967), Matsumoto et al.(1988) Magnetic buoyancy > Gravity force Vertical component of magnetic field : Fluid particle Low Magnetic Gas flow buoyancy High P B ∝ B 2 Gravity : unstable Gravitational energy : stable → kinematic energy

MHD simulation in the GC region (Suzuki+2015, cf, Machida+2009) SETUP ❖ Simulated l-v diagram ✓ Ideal MHD & locally isothermal gas Column density (10 21 cm -2 ) 300 100 LoS velocity (km s -1 ) ✓ Axismetry gravitational potential 200 10 100 0 1 -100 (Miyamoto & Nagai 1975) -200 Initial magnetic field: 0.1 -300 4 2 0 -2 -4 Initial gas profile: hydrostatic equilibrium Galactic longitude (degree) Non-circular motion : excited by magnetic activity Observational features(e.g. parallelogram structure) reproduce

Overview: Radius vs velocity (Averaged 0< φ<2π, |z| < 1 kpc) Initial rotational speed: ~ 50-200 km/s RMS (root mean square)Vertical speed: ~ 10-30 km/s Vertical motion excited by magnetic activity

Overview: Mass flux to vertical direction ~ upflow speed Free fall velocity ~ downflow speed

Overview: Gas flows and structure in global --track the motions of fulid elements with t=399.5-402.5Myr. ✓ Ubiquitously, vertical flows exist Average life ~ 4-6 Myr

Overview: Gas flows and structure in global --track the motions of fulid elements with t=399.5-402.5Myr.

Overview: Gas flows and structure in global --track the motions of fulid elements with t=399.5-402.5Myr. ~ upflow speed Free fall velocity ~ downflow speed

Overview: Gas flows and structure in global --track the motions of fulid elements with t=399.5-402.5Myr. Region X

Overview: Gas flows and structure in global --track the motions of fulid elements with t=399.5-402.5Myr. Region X Observer

Simulated l-v diagram High LoS velocity (t ＝ 401.0 Myr) 100 300 Column density (10 21 cm -2 ) 200 LoS velocity (km s -1 ) y 10 100 90 135 45 0 1 180 0 -100 225 315 -200 270 x 0.1 -300 4 2 0 -2 -4 視点 (270 ° ) Galactic longitude (degree) (r=8.0kpc)

Simulated l-v diagram (t ＝ 401.0 Myr) High LoS velocity 100 300 Column density (10 21 cm -2 ) Large 200 LoS velocity (km s -1 ) velocity dispersion y 10 100 90 135 45 0 1 180 0 -100 225 315 -200 270 x 0.1 -300 4 2 0 -2 -4 Obs.(270 ° ) Galactic longitude (degree) (r=8.0kpc)

Magnetic field line in region X Region X MF1 Z (kpc) zoom MF2 Z (kpc) Distance along Magnetic Fieldline (kpc) ✓ Magnetic arch-like structure !

Rising loop & Fast downflows MF1 MF2 Z (kpc) Z (kpc) Velocity (km/s) Velocity (km/s) Distance along Magnetic Fieldline (kpc) Distance along Magnetic Fieldline (kpc) ✓ Loop -foot (A): downflows ~100 km/s The gases fall down to one side ✓ Loop-top (B): Rising ~ 50 km/s Vertical velocity ↑

Rising loop & Fast downflows MF1 MF2 Z (kpc) Z (kpc) Number density (cm -3 ) Number density (cm -3 ) Distance along Magnetic Fieldline (kpc) Distance along Magnetic Fieldline (kpc) ✓ Downflows with high density ✓ The gases collect and compress

Rising loop & Fast downflows MF1 MF2 Z (kpc) Z (kpc) Number density (cm -3 ) Number density (cm -3 ) Distance along Magnetic Fieldline (kpc) Distance along Magnetic Fieldline (kpc) ✓ Downflows with high density ✓ The gases collect and compress

Discussion – Region X in l-v diagram ✓ Different features depending on the viewing angle. Obs.3 (250 ° ) Obs.2 (210 ° ) Column density (10 21 cm -2 ) 100 300 LoS velocity (km s -1 ) 200 10 100 y 0 1 -100 90 135 45 -200 0.1 -300 180 0 4 2 0 -2 -4 4 2 0 -2 -4 225 315 270 Galactic longitude (degree) x Obs.2 (210 ° ) ・ Shape (r=8.0kpc) Obs.3 (250 ° ) ・ Velocity dispersion (r=8.0kpc)

Summary High velocity 100� 300� cm -2 ) Large 200 � s -1 ) � Gas flows � (10 21 � (km� velocity dispersion 10 � � 100� density� velocity� 0� compression � Magnetic buoyancy � 1� Column� -100� LoS� -200� Gravity � 0.1� -300 � 4� � � � � � 2� � � � � � � � � � 0� � � � � � � � -2� � � � � � � � � -4 (Magnetic Activity; Parker Instability) Galactic� longitude� (degree) Downflows along the line of sight High velocity Large velocity dispersion Fall down align the magnetic slope Acceleration : ~100 km/s Footpoint of slope: collect and compress gases 4 2 0 -2 -4

Appendix: Basic Equation Eq. of continuity Eq. of motion Eq. of Induction Axisymmetry gravitational potential (Miyamoto & Nagai 1975)

Magnetic Field in The Galactic Centre Region ❖ Strong magnetic fields ✓ globally > 50μG ( Crocker+ 2010 ) ✓ Locally ~ 100-1000 μ G ( Yuzef-Zadeh+ 1984; Morris 1990; Pillai+15 ) ( ※ a few μG in a typical molecular cloud at the disk) ❖ Amplification of Magnetic fields Parker Instability Differential rotation MRI