初代星・初代銀河研究会2019@名古屋大学

ブラックホール超臨界降着
モーメンタムフィードバックの効果
Super-Eddington accretion to black holes:
Eﬀects of mechanical feedback
Eishun Takeo (Kyoto Univ.)
Kohei Inayoshi (KIAA), Shin Mineshige (Kyoto Univ.),
Ken Ohsuga (Tsukuba Univ.), Hiroyuki R. Takahashi (Komazawa Univ.)Supermassive black holes (SMBHs) in high-z Universe
Observation
Cosmic age < 1Gyr (z > 6), SMBHs with(Mortlock et al. 2011)

One possible pathway to high-z SMBHs: Rapid accretion
BH seeds (light seed, heavy:)

Rapid growth via gas accretionGoalSeed

Eddington limited growth→ growth time > Cosmic age of SMBHs→ Super-Eddington accretionis required.
Cosmic age

Possibility of super-Eddington accretion
Low mass BH：Eddington limited

Gas Density

Gas accretion → Disk → Radiation feedback

NeutralRegion

Hot & Ionized region → Suppression of Accretion(e.g., Milosavljevic et al. 2009)

Rotational axis

Sub-Eddington accretion

IonizedRegion

EquatorHigh mass BH
Bondi radiusBlack Hole> Ionization radius

High→Ionized
BH massregion
or collapses
high gas density→ Transition to Super-Eddington accretion phase.

:Bondi radius(Inayoshi et al. 2016)

Our study: Eﬀects of Mechanical feedback
Previous studies on super-Eddington transitions
do not include mechanical feedback.
cf. studies on accretion ﬂows @ Bondi scale(e.g., Novak+2012, Ciotti+2017)cf. eﬀects of jets in atomic-cooling halo
(Regan+2019)

Mechanical feedback has the potential
to shut oﬀ the inﬂowing gas
and blow out the surrounding medium.
Bipolar outﬂows→ Anisotropic ﬂow structure forms→ Inﬂowing motion round the equator?
cf. anisotropic radiation feedback cases

Gas Density distribution
exposed to anisotropic radiation

Radiation

Inﬂow(Sugimura+2017, Takeo+2018)

Our aim;
Derivation of the criterion required for the super-Eddington transition

Simulation setups
BH embedded in an uniform, metal-free gas cloud.
Two-dimensional radiation hydrodynamical simulation.

Gas cloud• Disk spectrum model as a function ofand(Watarai 2006)• Computational domain
BH• Frequency range• Isotropic radiation ﬁeld

BH

Slim disk

Standard disk

Outﬂow modelOutﬂow mass rate
Outﬂow kinetic power
Outﬂow kinetic energy
Ostriker et al. (2010)

Model parameters;: Outﬂow energy eﬃciency: Mass loading factor(outﬂow/accretion)

BH降着率→輻射

BH DISK: Outﬂow velocity 1,000km/s

Outﬂow modelOutﬂow mass rate
Outﬂow kinetic power
Outﬂow kinetic energy
Ostriker et al. (2010)

Angular dependence;cf. Sugimura+2017

BH DISK

Results: Time evolution of ﬂow structure (Outﬂow angle
Gas density

Gas temperature• Isotropic radiation → Spherical ionized region• Outﬂowing region along the polar axis / Inﬂowing region around the equator• Ionization radius is conﬁned within the Bondi radius→ Ionized region shrinks→ Transition)

Radial structure of outﬂows
along the rotational axis

• Ionized gas is evacuated by outﬂows.
• Cold region due to expansion cooling:

DensityCavity

Hot region due to shock:• Outﬂow speed is nearly constant.
(cf.

DensityHot)

Temperature

Cold~1,000km/s
Escap
evelocit
yDotted: Outﬂow
Solid: Inﬂow

Radial structure of outﬂow velocity
along the rotational axis

• Fast outﬂow with 1,000 km/s.
• Mild outﬂowing region
driven by pressure gradient.
• Inﬂowing motion by the BH gravity.

Ionized gas

Outﬂow

Ram pressure

Ambient gas

Inﬂow
Gaspressure
Escapevelocit
yDashed: Outﬂow
Solid: Inﬂow

Bondi radius

Radial structure of outﬂows
around the equatorial plane
Same as radiation-regulated accretion ﬂows.
e.g., Park & Ricotti (2011,2012)• Gas is photo heated up to• Ionized gas is depleted due to bothaccretion to the central BH
and outﬂow driven by thermal pressure.
Gas depletion
Accretion rate, Luminosity ↓Dense gas at the ionization front
falls into the central BH.
Accretion rate, Luminosity ↑Episodic Accretion

Dashed: Outﬂow
Solid: Inﬂow

Outﬂow opening angle→ Transition epoch becomes earlier

Outﬂow
Inﬂow

Transition epoch• Outﬂow opening angle → Solid angle of the inﬂowing region• Mass inﬂow rate reduces due to outﬂows
BH accretion rate

→ Radiation feedback→→ Transition

Transition criterion is alleviated owing to outﬂows

Critical density above which the transition occurs(w/o outﬂow)(w/ outﬂow)

Transition criterion is alleviated owing to outﬂows• Solid angle of inﬂowing region• Mass loss due to outﬂows→ Ionization radius
Critical density→ agrees with our numerical results.

SummaryEﬀects of mechanical feedback on the super-Eddington transition
cf. Only radiation feedback is considered in previous works.
(e.g., Inayoshi+2016)

2D radiation hydrodynamical simulation + chemical+ mechanical feedback model (Ostriker+2010).

Our Results• New transition criterion(w/o outﬂows)(w/ outﬂows)• Transition criterion is alleviated because
・accretion rate reduces due to signiﬁcant mass-loss
・solid angle of inﬂowing region[Future work]• Long-term simulation (after the transition)• Survey in broader range of BH masses