大質量星形成における複合フィードバックとその金属量依存性

田中圭 (大阪大学 / 国立天文台)

J. C. Tan (Chalmers/Virginia), Y. Zhang (RIKEN), T. Hosokawa (Kyoto),
V. Rosero (Virginia), J. E. Staff (Virgin Islands), J. M. De Buizer (SOFIA), M. Liu (Virginia), K. Tomida, K. Iwasaki (Osaka) and more

The standard scenario of massive star formation will soon be established!!

Multiple Feedback

MHD outflow, radiation pressure, ionization, stellar wind

Massive SF is similar to low-mass SF!!
but also depends on metallicity, etc.

Massive Stars& Their Formation

Massive Stars are Important!!
Massive stars (>10M⊙) are rare (~1%)
but very bright (>10,000L⊙)UV radiation, stellar winds, SNe, metal/dust, BHs, NSs, etc.
30 Dor & R136a~300M⊙
at ~50kpc

GW150914 ~ 36M⊙ + 29M⊙
at ~400Mpc (z~1)

Orion Nebula
at ~500pc

However, massive SF is poorly understood…

?

Observational Difﬁculties/Progress

Faraway

rare
short-lived

Complexembedded
jam-packed

BUT
ALMA is making
a lot of progressObservational Difﬁculties/Progress

Faraway

rare
short-lived

Complexembedded
jam-packed

BUT
ALMA is makinga lot of progress

Hirota+17, NatAsObservational Difﬁculties/Progress

Farawayrare
short-lived

Complexembedded
jam-packed

BUT?
sei

Hirota+17, NatAsuobawo
Hroehtt

ALMA is making
a lot of progress

Feedback Problem

Feedback in Low-Mass Star Formation
SFE ~ 0.4
Machida&Hosokawa13

low-mass SF

MHD Disk Wind
Andre+10

SFE~0.4

Feedback in Low-Mass Star Formation
SFE ~ 0.4
Machida&Hosokawa13

low-mass SF

MHD Disk Wind

also in massive SF!!

Matsushita+17

Staff, KT & Tan, arXiv:1811.00954

Hirota+17

Zhang, Tan, KT+, arXiv:1811.04381

Feedback in Massive Star Formation
Disk Accretion
Rosen+16

low-mass SF

MHD Disk Wind

also in massive SF!! Matsushita+17, Hirota+18

massive SF

Radiation Pressure
Krumholz+09, Kuiper+10, etc

Feedback in First Star Formation
typically ~50-100M⊙
from 1000M⊙ core
Hosokawa+16

low-mass SF

MHD Disk Wind

also in massive SF!! Matsushita+17, Hirota+18

massive SF

Radiation Pressure
Krumholz+09, Kuiper+10, etc

First SF in the early universe

Photoevaporation
McKee&Tan08, Hosokawa+11, etc

Multiple Feedback in Massive SF
Those processes were studied separately,
but all feedback acts together in reality.

low-mass SF

MHD Disk Wind
massive SF

Radiation Pressure + Stellar WindFirst SF

Photoevaporation

How do all feedback mechanisms work together?
Which is the dominant feedback?
Does feedback set the upper mass limit? or shape IMF?
How do they depend on metallicity and clump density?

Multiple Feedback in Massive SF
Those processes were studied separately,
but all feedback acts together in reality.

low-mass SF

MHD Disk Wind
massive SF

Radiation Pressure + Stellar WindFirst SFPhotoevaporation

recall Fukushima-kun’s talk
How do all feedback mechanisms work together?
Which is the dominant feedback?
Does feedback set the upper mass limit? or shape IMF?
How do they depend on metallicity and clump density?

ModelOverview of Our Semi-Analytic Modelcore collapse+ disk form. + MHD wind + photo-evap.
+ star evol. + rad press. + stellar windiiiii

acc. rate: m* = M env cosθ esc − mdw −mpe − msw
We solve the evolution of protostars,
accretion flow structures,and feedback processes self-consistently
until the end of accretion.
and evaluate SFEs from initial cores
The dominant feedback?
The upper-mass limit by feedback?
The metallicity dependence?

Pre-stellar cloud coreMc = 10 - 1000M⊙∑cl = 0.1 - 3 g/cm2
Z = 1e-5 - 1 Z⊙

InfraredDarkCloudsImpact of Multiple Feedback

at Z⊙
KT, Tan, & Zhang, 2017, ApJ, 835, 32

Accretion History
acc. rate [x10-3M⊙/yr]

2
1000M⊙,1g/cmkcabdeefo
only MHD disk windn470M⊙

full feedback
290M⊙
stellar mass [M⊙]Radiation feedback reduces SFE
SFE=0.47→0.29 in this caseStar Formation Efficiencies
0.6
only MHD wind

SFE from Core

0.50.40.30.2lower SFE in higher-mass SF
due to radiation feedbackfull fee

No upper limit by feedback
dbUnlike models with a truncation at 100M⊙
cf. stars with >100M⊙ in 30 Dor

ack0.1
01

10100
ﬁnal mass [M⊙]1000

Star Formation Efficiencies
0.6

SFE from Core

0.5
0.4

cl=3g/cm2

10.3

lower SFE in higher-mass SF
due to radiation feedback
small

0.1

Unlike models with a truncation at 100M⊙
cf. stars with >100M⊙ in 30 Dor

0.30.2lower SFE at larger core

0.101

No upper limit by feedbacklarge

10100
ﬁnal mass [M⊙]1000

difficult to form very-massive stars
by the competitive accretion
reasonable agreement with recent sims
by Kuiper & Hosokawa 2018

Mc=1000M⊙

Momentum-driven
outflow is dominantdniw
kiserdu
Dss
Her
M
py.
bdaw
ro+tflOudinrw

potho.
pav-estellalog mass-loss rate [M⊙/yr]

Which is the dominant feedback?

MHD disk wind?
orRadiation pressure?

log momentum [M⊙km s-1]

Which is the dominant feedback?
Mc=1000M⊙−11.8⎛⎞
ftrap L c
⎛ m* ⎞p radm*! i∼ 0.01⎜ −3i-1 ⎟⎜⎝ 30M ⎟⎠10Myr⎜⎟⊙⊙
p MHD φ m * vK*
⎝⎠
iiM

DH

dinsidw
kMHD disk wind
is dominant!!
Massive star formation
is similar to low-mass SF!!

rad. pressureat Z⊙

Metallicity Dependence
KT, Tan, Zhang, & Hosokawa, 2018, ApJ, 861, 68

Feedback at Low Metallicities
core mass=1000M⊙

Photo-evap.
MHD+RPOutﬂowAt Z⊙,
outflow is strongest
At <0.01Z⊙,
PE becomes dominant
Dust attenuation regulates PE rateStari

M evp,Z=0M evp ~1+ τ diτd≪1 at Z<1e-3Z⊙

SFEs at Various Metallicities
Feedback does not set
the upper-mass limit!
lower SFE in higher-mass SF
due to stronger feedback
lower SFE at lower Z
due to efficient photo-evap.

Non-Universal IMF?
IMF = CMF x SFEassumIMing

SalpeFgat etslo stwe eer Z perterCMAt sol to sub-sol metal of 1– 0.1Z⊙,
Z dependence is not apparent.
∑cl dependence is more significant
FAt extremely low Z case of 10-5– 10-3Z⊙,
massive stars would be rarer
Typical metallicity of 2nd stars (Chiaki+18)

Synthetic & Actual
Observations
synthetic observation:
KT+16, ApJ, 835, 32; KT+17, ApJ, 849, 133; etc.
actual observation:
De Buizer+KT17, ApJ, 843, 33;
Rosero, KT+, submitted to ApJ, arXiv:1809.01264;
Zhang, Tan, Sakai, KT+, submitted to ApJ, arXiv:1811.04381;
Zhang, Tan, KT+ submitted; etc.

Synthetic & Actual Observations
Synthetic Observations
4μm

10μm

40μm

10GHz8M⊙

12M⊙

16M⊙

24M⊙

IR survey by SOFIA

follow-up by
ALMA & VLASummary

Multiple Feedback in Massive SF
We develop the model of massive SF with multiple feedback
Feedback does not set the upper mass limit
MHD disk wind is dominant = similar to low-mass SF!!
At <0.01Z⊙, SFE is lower due to effective PE
Observation projects are also on-going

The standard scenario ofmassive star formation willsoon be established!!