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The Formation and Early Evolution
of Protostars and Protoplanetary Disks
Shu-ichiro Inutsuka (Nagoya Univ.)
M. Machida (Kyushu Univ), T. Matsumoto (Hosei Univ.)
June 18, 2012
@Crete, Greece
Outline
• Basic Problem of Star Formation
• 1st Collapse  1st Core
2nd Collapse  2nd Core=Protostar
• Outflows vs. Jets
Properties & Driving Mechanism
• Formation of Magnetized PPD and
Fragmentation
• Summary
Basic Problems in Star Formation
1. Angular Momentum Problem:
Protostar:
h* = W* R*2 ~ (1011cm)2/(105s) ~ 1017 cm2/s
Molecular Cloud:
hcore = dvcore Rcore ~ 0.1km/s 1017cm ~ 1021 cm2/s
 h* ~ 10-4 hcore
2. Magnetic Flux Problem
Protostar: F* ~ B* R*2 ~ kG(1011cm)2
Molecular Cloud: Fcore ~ Bcore Rcore2 ~ 10mG(1017cm)2

F* ~ 10-4 Fcore
Temperature Evolution at Center
geff =1.1 < gcrit =4/3
geff = 7/5
Effective Ratio
of Specific Heats
geff = 5/3
First Collapse
First Core
Second
Core
Second Collapse
Dissociation of H2
Ebind = 4.48 eV
dense
core:
n=105/cc
Masunaga, Miyama, & SI 1998, ApJ 495, 369; Masunaga & SI 2000, ApJ 531, 350
Effect of Non-Ideal MHD
Weakly Ionized Gas
Ionized
– Low density…
Ambipolar Diffusion
– Intermediate…
Hall Current Effect
– High density…
Ohmic Dissipation
1st Core
Temperature
Re,M
e.g., Nakano, Mouchouvias,
Wardle, Tassis, Galli,…
Second
Core
Dead
Zone
h
Number Density, n[/cc]
History of Ionization Degree
Because of uncertainty of dust grain properties,
we have parameterized resistivity.
Okuzumi 2012
Machida, SI,
& Matsumoto
(2007) ApJ
670, 1198
Stage 1: Outflow driven from the first core
The evolution of the Outflow around the first core
This animation start after the first core is formed at
Grid level L =12 (Side on view)
n~1010
cm-3
Model for
(a, w)=1, 0.3
Grid level L =12 (Top on view)
L = 1 (~104 AU)
L = 12 (360AU)
360 AU
Same as in Tomisaka 2002
Stage 3: Jet driven from the protostar
The evolution of the Jet around the protostar
This animation start before the protostar is formed at
Grid level L =21 (Side on view)
0.35 AU
n~1019
cm-3
Model for
(a, w)=1, 0.003
Difference in Driving Mechanism
Magnetocentrifugally
driven Wind
Magnetic Pressure
driven Wind
Strong B
Outflow
Wide Opening Angle
Jet
Weak B
Narrow Opening Angle
outflow around first core
Br  Bz  Bf
jet around protostar
Bz << Bf
only at launching region,
not in distant region
Machida, SI, & Matsumoto (2008) ApJ 676, 1088
Summary of Our Theory
Two different flows (outflow/jet) appear in the collapsing cloud
owing to the Stiffening of EoS.
Outflow driven by the first
core has wide opening angle
and slow speed.
Jet driven by the protostar
has well-collimated structure
and high speed.
The velocities of the outflow
and jet correspond to the escape
speeds from the first core, and
protostar.
Machida, SI, Matsumoto (2008) ApJ 676, 1088
Observational Proof  Velusamy, T., et al. 2007 ApJ 668, L159,
Velusamy, T. et al. 2011 ApJ 741, 60
Formation & Gravitational
Evolution of Disks
Formation of a Protostar
jet
Outflow
360 AU
first core
v~5 km/s
protostar
v~50 km/s
Machida et al. (2006-2012), Banerjee & Pudritz (2006), Hennebelle et al. (2008),
Duffin & Pudritz (2011), Commerçon et al. (2011), Tomida et al. (2011)
Outflows & Jets are Natural By-Products!
Formation of Planetary Mass
Companions in Protoplanetary Disk
tc~105
yr
Protoplanetary Disk
Protostar
~0.1 Msun
Protoplanet
M~8 MJup
300 AU
Machida, SI, Matsumoto (2009)
Rsep～10-20 AU
Resistive MHD Calc. from Mole. Cloud Core
SI, Machida, & Matsumoto (2010) ApJ 718, L58
End of Formation Phase
Disk Growth Correlated with
Depletion of Envelope Mass
Machida, SI & Matsumoto (2011)
Formation of Protoplanetary Disk
L
Mdisk = M*=0
Mdisk < Menv
Mdisk > Menv
Rdisk
L ~ lJ
102AU
101AU
dead zone
t = t*
t
SI (2012) PTEP Review
Protostar Formation in Self-Similar Solution
Larson-Penston
Shu
Whitworth & Summers 1985, MNRAS 214, 1
I recommend Sec 7.4 to theorists!
Formation of Planetary Mass
Companions in Protoplanetary Disk
SI, Machida, & Matsumoto (2010) ApJ 718, L58
Evolution of
Stellar Mass &
Disk Mass
Local Criterion for
Gravitational Instability:
Q  k Cs /(pGS)
SI, Machida, & Matsumoto (2010) ApJ 718, L58
2D Modeling by Vorobyov & Basu 2006
Solution to
Luminosity
Problem?
2D Simulations of Infinitesimally Thin Disk
TimeVariability
Observational Clue:
variability in deeply
embedded protostar!
Machida, SI & Matsumoto
(2011) ApJ 729, 42
Orbits of Planets & Their Fates
Multiple Episodes of
Planet Formation and
Orbital Decay
Machida, SI & Matsumoto (2011) ApJ
729, 42
Summary
• Outflows from First Core & Jets from Protostar
– Ang. Mom. & Mag. Flux Problem
• The First Core becomes Protoplanetary Disk!
 Mdisk > M* in disk formation phase
Successive Formation of Planetary-Mass Objects
• Episodic Accretion and Planet Falling
 Outburst of Protostellar Luminosity
Consider “Jupiters” from the outset of core-accretion.
Initial Rotation Speed
In Reality…
Observed Mass Ratio
White & Ghez 2001
What is the actual
initial condition for
planet formation?
Initial Magnetic Field Strength
Machida+ 2008, ApJ 677, 327
w
Machida+ 2008, ApJ 677, 327
Type classification (B, w and Am2)
Core shapes are plotted
against different magnetic
field strength, rotation speed
and non-axisymmetricity
Am2=0
z=0
plane
35 AU
Am2=0
B
35 AU
Am2=0.01
B (a): ring disk => core
(magnetic braking, magnetic pressure)
w: core => ring, bar
Am2=0.2
Am2
(centrifugal force)
35 AU
Am2: ring, core =>bar
Q2: Obs of Magnetic Flux Loss?
Magnetic flux
Magnetic flux largely removed from First Core
when n =1012 ~ 1016 cm-3
 B = kG or less
Ideal MHD
Resistive MHD
Machida, SI, & Matsumoto (2007) ApJ 670, 1198
Can we observe this by ALMA?