1. Masahiro Machida (Kyoto Univ.) Shu-ichiro Inutsuka (Kyoto Univ.), Tomoaki Matsumoto (Hosei Univ.) Outflow jet first coreprotostar v~5 km/s v~50 km/s 360 AU Protostellar Jet in the Collapsing Cloud Core 1000 times close-up

2. ? Star Formation and Jet / Outflow Before the star formation Just after the star formation Molecular Cloud Core Hirano et al. (2006) Jet from protostar Stars born in the molecular cloud core Jet / Outflow always appears in the star formation process Jet / Outflow plays crucial roles in the star formation  They are closely related to the stellar mass  They transport the angular momentum from the cloud core ・・・・ (Nagoya Univ.) We cannot observe Jet /outflow driving phase

3. Protostellar Outflows and Jets Velusamy et al. 2007 In star-forming regions, there are two distinct flows: Outflows and Jets ◆ Molecular Outflow ： low velocity (~10 km/s), wide opening angle ◆ Optical Jet: high velocity (~100 km/s), well-collimated structure Optical Jet is enclosed by Molecular Outflow But, Mechanism is still unknown outflow jet protostellar disk Protostar outflow jet dark cloud protostar Purpose of This Study Understanding the driving mechanism of Jets / Outflows Using the numerical simulation, we calculated the cloud evolution from the molecular cloud (n=10 4 cm -3, r~10 4 AU) until the protostar (n~10 20 cm -3, r ~ 1R sun ) formation HH30, Pety et al. 2006

4. Dead region B dissipation (10 12 cm -3 <n<10 15 cm -3 ) B amplification B B B Log T (K) Log n (cm -3 ) 10 10 15 10 20 10 5 10 10 2 10 3 10 4 Isothermal Phase Adiabatic PhaseSecond Collapse & Protostellar Phases Adiabatic core (First core) Formation H 2 dissociation To MS protostar formation Gas Temperature 1D Radiative Hydrodynamics Spatial Scale (AU) 10 4 10010.1 Larson (1969) Tohline (1982) Masunaga & Inutsuka (2000) cloud core Thermal Evolution in the Collapsing Cloud Protostar

5. Magnetic Evolution Resistivity Magnetic Reynolds number  : resistivity v: free fall velocity L: Jeans Length ◆ Magnetic Reynolds number Ohmic dissipation Well-Coupled ◆ Resistivity is fitted as a function of n and T (Nakano et al. 2002)  Coupling between the magnetic field and neutral gas (weakly-ionized plasma)  Low density (n  col  Moderate density (10 12 cm -3 <n < 10 16 cm -3 ) ： Ionization rate decreases as density increases ⇒ Dissipation of B by Ohmic dissipation  High density (n>10 16 cm -3 ) ： Some metals are ionized, Well-coupled Resistivity  Reynolds number Re Cloud Protostar Cloud evolution B B B ◆ Basic equations

6. Gas sphere in hydrostatic equilibrium  Critical Bonner-Ebert Sphere + Rotation + Magnetic Field  Magnetic field lines are parallel to the rotation axis: B //   Parameters: α, ω  α=B c 2 /(4  c s  ) :magnetic field strength (ratio of the magnetic to thermal pressure)   =  /(4  G  ) 1/2 : angular velocity normalized by freefall timescale   Initial Value  Number density ： n=10 4 cm -3  Temperature ： T=10K Bonnor-Ebert Sphere Rotation Axis Magnetic Field Line Ω B 4.6x10 4 AU L=4  (B x,0, B y,0, B z,0 ) = (0, 0, (  4  c s  ) 1/2 )  (  x,0,  y,0,  z,0 ) = (0, 0,  ( 4  G  ) 1/2 )  Cloud scale: 4.6x10 4 AU  Mass ： M tot =14 M sun Initial Settings

7. 同時刻、異なるグリッドスケール L = 1 L = 2 L = 3 L = 31 L=4 Schematic view of Nested Grid At the same epoch but different spatial scales Example of Nested Grid 3D Resistive MHD Nested Grid Method  Grid size: 128 x 128 x 64 (z-mirror sym.)  Grid level: l max =31 (l : Grid Level)  Total grid number: 128 x 128 x 64 x 31 For uniform grid, (128x2x10 30 )x(128x2x10 30 )x(64x2x10 30 ) ~ (10 30 ) 3 cells are necessary  Grid generation: Jeans Condition l =1: L box = 4 pc, n = 10 3 cm -3 (initial) l =31: L box = 0.2 R sun, n = 10 23 cm -3 (final) 10 orders of magnitude in spatial scale 20 orders of magnitude in density contrast Numerical Methods

8. Cloud Evolution from Molecular Cloud to Protostar n c =10 4 cm -3 n c =10 9 cm -3 n c =10 11 cm -3 n c =10 13 cm -3 n c =10 15 cm -3 n c =10 17 cm -3 n c =10 21 cm -3 n c =10 22 cm -3 Initial StateIsothermal Collapse First Core Formation Adiabatic Collapse Outflow Driving Magnetic Dissipation Second Collapse Protostar & Jet

9.  n= ~5x10 11 cm -3  n= ~5x10 11 cm -3 :First core formation, B field begins to be twisted  10 11 cm -3 <n< 10 13 cm -3  10 11 cm -3 <n< 10 13 cm -3 : B field strongly twisted, outflow appears  10 13 cm -3 <n< 10 16 cm -3  10 13 cm -3 <n< 10 16 cm -3 : B Field is dissipated by the Ohmic dissipation (Br, B  ) ⇒ The magnetic field lines are uncoiled (Bz becomes major component )  10 16 cm -3 <n< 10 20 cm -3  10 16 cm -3 <n< 10 20 cm -3 : Second collapse, B is coupled with the neutral gas, amplified again  n>10 20 cm -3  n>10 20 cm -3 : Protostar formation, B r, B   increase again 100 AU Evolution of the Magnetic field at center of the cloud Grid level L =14 (Side on view) Magnetic flux against the central density  Magnetic flux is largely removed from the first core for 10 12 -10 16 cm -3 Ideal MHD model Resistive MHD model Dissipation by the Ohmic Dissipation

10. Low-velocity Flow from First core High-velocity flow from Protostar ~1000 times close-up of the central area 360 AU0.35 AU  First Core ： n~10 11 cm -3, r~10-100 AU  Protostar ： n~10 21 cm -3, r~0.01 AU Outflow and Jet Driving Phase v outflow ~ 5 km/s v Jet ~50 km/s Two distinct flows appear in the collapsing cloud!! L=12 L=22

11. Adiabatic core (first and protostar core) formation ⇒  rot <  collapse ⇒ Magnetic field lines are twisted ⇒ Flow driving Each core has different scale and different magnetic field strength  First Core does not experience the Ohmic dissipation: Strong field, hourglass  Protostar experiences the Ohmic dissipation: Weak field, straight lines Driving Phase of Each Flow 1000 times close-up 10 3 -10 5 yr

12.  Different degrees of the collimation are caused by different driving mechanisms Around First Core (Outflow) Lorenz ≒ Centrifugal ≒ Thermal Pressure (inflow) Around Protostar (Jet) Centrifugal ≒ Thermal Pressure >> Lorentz (inflow) Magnetocentrifugal wind ⇒ First core, Outflow Driving Mechanism Magnetic pressure gradient wind + MRI ⇒ Protostar, Jet Disk Wind Strong B Wide Opening Angle B gradient Weak B Narrow Opening Angle ・ Strong B ・ flow along B lines ・ hourglass B ・ weak B ・ Flow along rotation axis ・ straight B Collimation  ~1-10  >1000 First CoreProtostar Forces

13.  Flow speed is determined by gravitational potential of each core (Kepler speed) First core: ~0.01 M sun, ~1 AU ⇒ v Kep ~ 5 km/s ⇔ v max = 5 km/s (simulation) Protostar: ~0.01 M sun, ~1 R sun ⇒ v Kep ~50 km/s ⇔ v max = 50 km/s (simulation)  We calculated the very early phase of the star formation  Flow speeds increases with core mass  The Kepler speed is proportional to ∝ M 1/2  When the first core and protostar grow up to ~1M sun Outflow ⇒ v Kep ~ 50 km/s Jet ⇒ v Kep ~500 km/s Flow Speed 20 AU First core Proto star

14. DriverSpeedcollimationMechanism Configuration of B OutflowFirst coreSlow (~10km/s) △ Disk Wind Hourglass JetProtostarHigh (~100km/s) ◎ Mag. pressure Straight  Our simulation could naturally reproduce properties of outflows and jets Properties of Outflow and Jet Schematic View  Low-velocity outflow is enclosed by the high-velocity Jet

15. Summary  To avoid artificial settings around the protostar, we calculated the cloud evolution (or jet driving) from the molecular cloud (n=10 4 cm -3 ) until the protostar formation (n~10 23 cm -3 )  Outflow is directly driven from the first core (not entrainmented by jet)  Two distinct flows: Outflow from the first core, Jet from the protostar Outflow: wide opening angle and slow speed Jet: well-collimated structure and high speed  The differences between outflow and jet is caused by different strength of magnetic field, and different depth of gravitational potential Different strength of magnetic field is caused by the Ohmic dissipation Deferent depth of the gravitational potential is cause by the thermal evolution of the collapsing cloud

16. 10000 AU Outflow driving point (small scale) Outflow propagation (middle scale) Velusamy et al. (2007) HH47 Interaction between outflow and molecular cloud Interaction between outflow and host cloud (large scale) 500 AU 8000 AU 2000 AU Initial Molecular Cloud Core Bow shock, Cavity, Turbulence unsteady