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Suzaku Study of X-ray Emission from the Molecular Clouds in the Galactic Center

Suzaku Study of X-ray Emission from the Molecular Clouds in the Galactic Center. M. Nobukawa , S. G. Ryu , S. Nakashima, T. G. Tsuru , K. Koyama (Kyoto Univ.), H. Uchiyama (Univ. Tokyo), V. Dogiel , C. Dmitry (P.N. Lebedev Institute) a nd Suzaku GC team.

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Suzaku Study of X-ray Emission from the Molecular Clouds in the Galactic Center

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  1. Suzaku Study of X-ray Emission from the Molecular Clouds in the Galactic Center M. Nobukawa, S. G. Ryu, S. Nakashima, T. G. Tsuru, K. Koyama (Kyoto Univ.), H. Uchiyama (Univ. Tokyo), V. Dogiel, C. Dmitry (P.N. Lebedev Institute) and Suzaku GC team

  2. Topics on 6.4 keV Emission 1. 6.4 keV Emission from the Galactic center region 1.1. Detailed X-ray view with Suzaku 1.2. K-shell lines from neutral heavy elements 1.3. Time variability 1.4. 3-D distribution of the 6.4 keV MCs • Prospective in the Astro-H era • Summary

  3. Topics on 6.4 keV Emission 1. 6.4 keV Emission from the Galactic center region 1.1. Detailed X-ray view with Suzaku 1.2. K-shell lines from neutral heavy elements 1.3. Time variability 1.4. 3-D distribution of the 6.4 keV MCs • Prospective in the Astro-H era • Summary

  4. 1. 6.4 keV Emission from the Galactic center region 6.4 keV Focus in this talk Sgr A* Bright X-ray binaries with no Fe line 6.7 keV Hot Plasma = Tsuru-san’s talk 100 pc= 300 lys

  5. Correlation with Molecular clouds 6.4 keV map • Correlation with Giant Molecular Clouds • Ionization of Fe atoms due to external particles (E>7.1 keV, Fe-K edge) → Fluorescence X-ray （Neutral Fe line） -> a high energy phenomenon hides Molecular gas（CSline） Tsuboi+99

  6. Origin of the 6.4 keV Emission Sgr B2 X-ray illumination(Koyama+96; Murakami+00) - pronounce Fe line (EW>1 keV) • deep Fe edge (equivalent to NH > 1024 cm-2) • peak shift to the GC from the MC core -> illuminated from the GC Luminal irradiating source (Lx~1039 erg/s) larger than LEddfor 1 M◎ => big flare of Sgr A* had occurred in the past? 2’=5 pc Gray scale: 6.4 keV Contour : MC core (Radio) Murakami+00 5 Energy (keV) 9 To GC

  7. Origin of the 6.4 keV Emission Sgr C Low-energy Cosmic-ray impact Electron (E= a few 10 keV): (e.g. Yusef-Zadeh+07) • Correlation with non-thermal radio filaments (synchrotron by GeV e-) • Heating of MCs / HE gamma-rays Proton (E=a few 10 MeV): (e.g. Dogiel+09) • Generation by Sgr A*, capturing a star X-ray (contour) Ratio(gray) • Need multiple information about the origin • Constraint of an irradiating source 10 pc Yusef-Zadeh+07 Suzaku observation

  8. Topics on 6.4 keV Emission 1. 6.4 keV Emission from the Galactic center region 1.1. Detailed X-ray view with Suzaku 1.2. K-shell lines from neutral heavy elements 1.3. Time variability 1.4. 3-D distribution of the 6.4 keV MCs • Prospective in the Astro-H era • Summary

  9. 1.1. Detailed X-ray view with Suzaku Papers: Koyama+07 M0.74 MN+08Sgr B1 Koyama+08 Time variability in Sgr B2 Koyama+09 Time variability in 10 years Nakajima+09 Sgr C Fukuoka+09 G0.174 Ryu+09 3-D distribution in Sgr B2 MN+10 K-shell Lines Nakashima+10 M359.07 MN+11 (submitted) Time variability Ryu+ in prep 3-D distribution in Sgr C (+ theoretical papers) Dogiel+09,11,chrenshov+11(submitted) • Suzaku found a number of MCs with 6.4 keVline Sgr B1 Common characteristics hard continuum ：　G = 1.5—2.5 strong 6.4 keV line：　EW =1—2 keV

  10. Topics on 6.4 keV Emission 1. 6.4 keV Emission from the Galactic center region 1.1. Detailed X-ray view with Suzaku 1.2. K-shell lines from neutral heavy elements 1.3. Time variability 1.4. 3-D distribution of the 6.4 keV MCs • Prospective in the Astro-H era • Summary

  11. 1.2. K-shell lines from neutral heavy elements Typical spectrum 6.4 keV line＋absorbed continuum Ar Ca Fe=1 Cr Ni Mn Heavy atoms other than Fecan provide a new constraint. *solar abundance Low energy lines are absorbed by ISM

  12. 1.2. K-shell Lines Neutral Fe S Si Ar Fe Ca He-/H-like ions X-ray spectrum of the brightest MC Suzaku 200ks MC component (Lines + Continuum) Abs. (ISM) Abs. (MC) Plasma x x

  13. 1.2. K-shell Lines Heavy elements in neutral state → K-shell line of neutral atoms plasma Ca continuum Ar Mn Line Cr 2 Energy (keV) 5 10 Also detected ionized Cr / Mn K lines

  14. Origin of neutral lines • 1.2. K-shell Lines Line: K-shell ionization due to external X-ray, electron, proton Continuum: X-ray ・・・Thomson Scattering Electron・・・Bremsstrahlung Proton ・・・Inverse Brems. Line External particles MC Continuum Different spectra are produced X-ray origin e- e- Mn Cr S Fe Fe Ca Ar Equivalent width = Abundance Electron origin

  15. Abundance from observed EWs X-ray model : 1.6 solar electron model: 4 solar

  16. Abundances 6.4 keV = cold medium (T~10 K) Metal abundances Sgr A* X-ray origin 1.6Z◎ electron origin 4Z◎ Proton origin< 2Z◎ 6.7 keV = hot plasma (T~107-8 K) 1—2 Z◎ 100 pc

  17. Topics on 6.4 keV Emission 1. 6.4 keV Emission from the Galactic center region 1.1. Detailed X-ray view with Suzaku 1.2. K-shell lines from neutral heavy elements 1.3. Time variability 1.4. 3-D distribution of the 6.4 keV MCs • Prospective in the Astro-H era • Summary

  18. 1994 (ASCA) 2000 (Chanrda) 2003(XMM) 2005(Suzaku) 1.3. Time variability • X-ray flux in the Sgr B2 MCs had decreased by a factor of ~0.5 in 10 years (Inui+09) Systematic uncertainty remains because of data taken from different satellites. Suzaku observation of the same position in 2005 / 2009

  19. 1.3. Time variability Observation in 2005/2009 with Suzaku • 6.4 keV line • ・Sgr B2/M0.74 • become darkened. • ・No change in the • surroundings • Hard X-ray • ・Sgr B2/M0.74 become darkened. • ・No significant • change in the • surroundings. 0 0.5 1 0 0.5 1 • Time variability both in 6.4 keV and hard continuum • Coherent decrease between the two MCs

  20. MC Size of ~10 lys⇔ time scale of variability <10 years • MCs should be irradiated by X-rays • not by protons (E~10 MeV; v = 0.1 c < light velocity). • Coherent decrease suggests a single origin for the two MCs.

  21. 1.3. Time variability Illuminating source – required luminosity Lx of illuminating source depends on the distance from the MC Sgr B2 case: • No such a bright XRB has been observed in the Sgr B2 vicinity. • No XRB with Lx~1039 erg/s has been found even in the GC region. • Possible scenario is a past big flare of Sgr A*, super-massive black hole with M=4x106M◎ erg/s > 4 x 1037 erg/s (d=15 pc; the closest case) 15 pc

  22. 1.3. Time variability Other results of time variability XMM (Pontiet al. 2010) • Integral (20—60 keV) (Terrier+10) • Decrease by half in 8 year Consistent with our result • XMM (6.4keV) (Ponti+10) • Super-luminal motion in MCs near Sgr A* (d~5 pc) • Chandra (2-10keV) (Muno+08) • MCs near Sgr A* • These facts also suggest the past X-ray flare of Sgr A*. 2004 2007 2009 2008

  23. Topics on 6.4 keV Emission 1. 6.4 keV Emission from the Galactic center region 1.1. Detailed X-ray view with Suzaku 1.2. K-shell lines from neutral heavy elements 1.3. Time variability 1.4. 3-D distribution of the 6.4 keV MCs 1.5. Diffuse emission other than MCs • Prospective in the Astro-H era • Summary

  24. 1.4. 3-D distribution of the 6.4 keV MCs • In order to investigate the detailed history of the past activity, we must know positions of MCs relative to the super-massive black hole. • Measurement of MC position: • MCs absorb a part of plasma emission

  25. 1.4. 3-D distribution MC Distribution and Past history of Sgr A* • Distribution of the MCs illuminated by X-rays indicate the history of the past Sgr A* activity. Preliminary Please see Ryu’s poster #37

  26. Topics on 6.4 keV Emission 1. 6.4 keV Emission from the Galactic center region 1.1. Detailed X-ray view with Suzaku 1.2. K-shell lines from neutral heavy elements 1.3. Time variability 1.4. 3-D distribution of the 6.4 keV MCs • Prospective in the Astro-H era • Summary

  27. 2. Prospective in the Astro-H era • Direct measurement of motion / position of MCs • Shift : 50 km/s <-> DE = 1 eV@6.4 keV c.f. velocity ~ 200 km/s • Shape of the Compton shoulder -> source direction • Chemical composition in GC • K-shell lines and absorption edge • Ratio of Comp. shoulder to 6.4 keV line –> Hydorogendensity in the MC

  28. Thank you for your attention 1. 6.4 keV Emission from the Galactic center region 1.1. Detailed X-ray view with Suzaku 1.2. K-shell lines from neutral heavy elements 1.3. Time variability 1.4. 3-D distribution of the 6.4 keV MCs • Prospective in the Astro-H era • History of the past activity of Sgr A* Measurement of the motion and position of MCs • Chemical abundances in the GC region

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