Flaring up of the Compact Cloud G2 during the Close Encounter with - - PowerPoint PPT Presentation

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Flaring up of the Compact Cloud G2 during the Close Encounter with - - PowerPoint PPT Presentation

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ALMA 2013/01/26-28 Flaring up of the Compact Cloud G2 during the Close Encounter with Sgr A* in 2013 Summer Takayuki Saitoh Tokyo Institute of Technology CollaboratorsJunichiro Makino(Titech),

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Flaring up of the Compact Cloud G2 during the Close Encounter with Sgr A* in 2013 Summer

Takayuki Saitoh Tokyo Institute of Technology

Collaborators：Junichiro Makino(Titech), Yoshiharu Asaki(JAXA), Junichi Baba(Titech), Shinya Komugi(NAOJ), Makoto Miyoshi(NAOJ), Tohru Nagao(Kyoto), Masaaki Takahashi(Aichi-Edu.), Takaaki Takeda(NAOJ), Masato Tsuboi(JAXA), Ken-ichi Wakamatsu(Gifu)

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

1999.4

Yutaka Tatsuta, Takayuki Saitoh, Tamon Suwa, Kimitake Hayasaki, Yu Morimoto Takuma Suda, Takatsugu Tokumaru, Masahiro Machida Takashi Okamoto Chiaki Hanyu

  • Prof. Masayuki Fujimoto
  • A. Prof. Asao Habe, Noboru Kaneko

Yachi-san, Kurino- san, Fukuda-san, Nishikawa-san ... Yasufumi Ikeda

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Contents

  • 1. Introduction
  • 1. Gillessen et al. 2012 Nature
  • 2. 2D Numerical simulation by Schartmann

et al. 2012 ApJ

  • 2. Results of our 3D simulation
  • 1. Saitoh et al. 2012 arXiv:1212.0349
  • 3. Discussion & Summary
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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

1a.u.=1.5x1013 cm =4.8x10-6 pc 1ME=6.0x1027 g =3.0x10-6M◎

Units

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

  • 3 Earth mass cloud

was found in the Galactic center

  • Rperi~270 au/Tperi~

2013 Summer

  • Giant radiation flare

would be observed due to the mass accretion onto the Sgr A*

5/Jan/2012 Nature

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

IR band images by VLT

Obs

Reconstructed

  • rbit

Gillessen et al. 2012

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28 Gillessen et al. 2012

P-V diagrams

  • Elongated structure has been observed
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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Cloudʼs and orbital properties

  • Mass：~3 earth mass
  • Effective Radius:~15mas ~125 AU
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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Summary of Obs

  • Three earth mass cloud, G2, was found in

the Galactic center, which is approaching the Sgr A* and will be pass the pericenter (~270 au) in 2013 summer.

  • Interaction with the ambient hot gas may

induce the destruction of G2 by KH/RT instabilities, resulting in the enhancement

  • f the activity in the Sgr A*.

– 38 citations (27 Jan 2013)

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Observing proposals for 2013

Gas Cloud Wiki

https://wiki.mpe.mpg.de/gascloud/FrontPage 28 Jan 2013

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

ESO animation

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Simulation

  • 2D, PLUTO(AMR)
  • 2 scenarios
  • 1. Compact cloud scenario
  • 2. Spherical shell cloud scenario
  • EOS : Isothermal
  • Hot ambient gas surrounding the Sgr A*

– Radiatively Inefficient Accretion Flow (RIAF)

  • Density/Temperature profile:~1/r (Yuan+2003)

– Profile is fixed.

Schartmann+2012

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28 Schartmann+2012

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28 Schartmann+2012

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

  • Spherical shell model can explain the

p-v diagram much well.

Compact Cloud Spherical shell Schartmann+2012

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

  • If ~10% of Mcloud falls into the Sgr A* and it releases 10 % of its

energy, the released energy is ~1048erg

  • 3x1039erg/s if we assume 10 years as the duration time.
  • However, if we adopt the typical the eff. of RIAF ~ 10-6, ~1034 erg/s.

Schartmann+2012

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Q

  • Is 2D approximation good for this

system?

– Tidal force in the vertical direction to the

  • rbital plan was excluded.

– Since the Vperi~5000km/s, the compression energy will be enormous even if only several % of Vperi can be used.

  • Here, we investigate the effects of three-

dimensionality.

– We adopt the compact cloud scenario, and do not care details in the formation process

  • f cloud.
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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

3D Simulation Setup

  • N-body/SPH simulations of the system with the

cloud, hot ambient and Sgr A*.

– Gravity, hydrodynamics and radiative cooling w/Optically thin

  • 3D uniform density cloud

– 3MEarth, Radius 125AU

  • Orbital parameter：Gillessen+2012

– Pericenter passage: A.D. 2013.5

  • Since A.D. 1995 to A.D. 2033
  • Hot ambient profile
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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Run parameters

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Parallel N-body/SPH code：

ASURA

  • C (C99) + MPI
  • Domain decomp.:Orthogonal Recursive

Bisection

  • Gravity: Parallel Tree+GRAPE

– Hardware accelerators : GRAPE-5/GRAPE-6A/GRAPE- 7/GRAPE-DR – Software accelerator : Phantom-GRAPE

  • Assembler tuned software library!!

– Symmetrized Plummer Potential (Saitoh&Makino 2012a)

  • Hydro：Density Independent SPH

(Saitoh&Makino 2012b)

  • Time integrator: Leap-frog

+Individual time steps +Time-step limiter (Saitoh&Makino 2009) +FAST (Saitoh&Makino 2010)

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

New SPH formulation

ρ=1 ρ＝4

  • Initially hydrostatic fluid

– Standard SPH fails to keep hydrostatic state – Our SPH successfully maintains hydrostatic state SSPH Our SPH

Saitoh & Makino 2012b

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Kelvin-Helmholtz Instability

Standard SPH Our SPH Saitoh & Makino 2012b

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Two Fluid Mixing by Spoon

Standard SPH Our SPH Saitoh & Makino 2012b

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Mass accretion rate

Halo

  • rigin

Cloud

  • rigin
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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

2006.26 2012.02 2012.74 2013.10 2013.46 2013.82

Luminosity Evolution

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Analytic Evaluation of Luminosity

  • Assume that…
  • 1. All elements have elliptical orbits and share the

same ascending node.

  • 2. Cloudʼs radius is 125 au at the point where the

semi-minor axis and orbits intersection.

  • 3. All energy released at the pericenter.
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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

The effects of Ram pressure

  • Ram pressure：
  • Energy/sec with a conversion factor C
  • Substituting the hot ambient profile and
  • rbit info. (r-vc; Burkert+2012):
  • 1. A.D.2000,r2000=6x1016cm、

σ=π(125AU)2、dE/dt =

  • 2. A.D.2013.5,r2013.5=4x1015cm,σ<1AUx40

AU=40AU2、dE/dt

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

New observations of the gas cloud G2 in the Galactic Center:Gillessen+2013 ApJ

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ALMA時代の宇宙構造形成理論研究会 2013/01/26-28

Summary

  • We performed 3D N-body/SPH simulations
  • f the 3 Mearth gas cloud G2 approaching the

Sgr A*.

  • Due to the strong compression in the

vertical direction by the tidal force, the cloud releases ~1035 erg/s during 2013.

– Main source is the recombination line from the hot gas heated to ~104K. – In particular, Paschen and Brackett series (infrared-bands), which do not suffer from the dust extinction effects significantly, are good to

  • bserve.