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Gabriele Ponti Marie Curie Fellow at University of Southampton

1. High energy evidence for past activity from Sgr A* or its surroundings. Gabriele Ponti Marie Curie Fellow at University of Southampton. R. Terrier, A. Goldwurm, G. Belanger and G. Trap. Sgr A* today: a dormant AGN. L SgrA* ~3  10 33 - 10 35 erg s -1. Sgr A* low luminosity.

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Gabriele Ponti Marie Curie Fellow at University of Southampton

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  1. 1 High energy evidence for past activity from Sgr A* or its surroundings Gabriele Ponti Marie Curie Fellow at University of Southampton R. Terrier, A. Goldwurm, G. Belanger and G. Trap

  2. Sgr A* today: a dormant AGN LSgrA*~31033 - 1035 erg s-1 Sgr A* low luminosity MSgrA*=4.4106 M Sun ~10-9 Ledd = 51044 erg s-1 Chandra

  3. Sgr A* today: in a broader context LSgrA*~31033 - 1035 erg s-1 Sgr A* low luminosity MSgrA*=3.6106 M Sun ~10-9 Ledd = 51044 erg s-1 How was the Sgr A* accretion rate in the past? Are we testimony of a peculiar moment of Sgr A*? Image from Gallo 2010 Sgr A* during normal flare deep in quiescence!

  4. The idea: Molecular clouds as mirrors of past activity • Sgr A* sits on the centre of the • Central Molecular Zone (CMZ) • 107-108 MSun of MC in the • central 300 pc • MC are mirrors of the GC past activity • How do the Sgr A* light fronts appears to us at infinity? Galactic plane from above Sgr A* Toward the Earth Sunyaev et al. 1993; 1998

  5. The idea: Molecular clouds as mirrors of past activity • Sgr A* sits on the centre of the • Central Molecular Zone (CMZ) • 107-108 MSun of MC in the • central 300 pc • MC are mirrors of the GC past activity • Iso-delay light fronts are parabola! Sunyaev et al. 1993; 1998

  6. The idea: Molecular clouds as mirrors of past activity • Sgr A* sits on the centre of the • Central Molecular Zone (CMZ) • 107-108 MSun of MC in the • central 300 pc • MC are mirrors of the GC past activity • Light fronts appears to us as • Parabola •  Tool to study history of GC emission Galactic plane from above nH r d Sgr A* Toward the Earth Sunyaev et al. 1993; 1998

  7. Reflection spectrum from neutral material Source Slab of neutral reflecting material A reflection spectrum should contain: Fe Kα+β emission lines Compton hump FeK edge Link between source incident flux and reflection intensity

  8. Open problems: Which is the origin of the Hard X-ray emission from MC? ASCA: Fe K from some MC GRANAT: Hard X-ray/MC Sunyaev et al. 1993 Koyama et al. 1996

  9. Chandra: Fe K toward SgrA* INTEGRAL: MC - reflection FeK: constant intensity! Murakami et al. 2001 Revnivtsev et al. 2004 Chandra: Sgr A cont. variability Multi-instruments: Sgr B2 variability Muno et al. 2007 Inui et al. 2009 Are MC reflecting GC radiation? Sgr B2 consistent with reflection But weak detection of variability

  10. Contours 850-micron; FeK map (red);20 cm (green) Alternatives to reflection: Cosmic Rays Cosmic ray electrons Yusef-Zadeh et al. 2002; 2007 Cosmic ray protons Aharonian et al. (2006) HESS TeV contours on FeK map

  11. X-ray from MC: Reflection or Cosmic Rays? • Low energy cosmic ray electrons or protons Low energy cosmic ray electrons: Yusef-Zadeh et al. 02; 07 Valinia et al. 00; Low energy cosmic ray protons: Dogiel et al. (2009) Supernovae ejecta: Bykov 02 • Sgr A* flare ~1.51039 erg s-1 ~ 100 yr ago Internal source External source: Sgr A*, X-ray binary, Sgr A East • I will present the new results on the field based on: • ~ 7 years (~20 Ms) of INTEGRAL monitoring of the GC region • study of the high energy Sgr B2 emission - accurate light curve • ~ 10 years (~1.2 Ms) of XMM-Newton monitoring of the 15’ region around Sgr A* • study the time variability of MC in Sgr A • disentangle the models • ~ 5 years Suzaku

  12. The INTEGRAL view of Sgr B2 FeK (xmm) Terrier, Ponti et al. 2010 No point source Decay time ~8.21.2 yr ~core light crossing time variability 4.8 

  13. The INTEGRAL view of Sgr B2 Terrier, Ponti et al. 2010 Spectral shape: both low energy cosmic ray electrons and reflection! But low energy cosmic ray electrons  huge cosmic ray electron luminosity (~91039 ergs s-1) Parallax measurement 120 pc in front of Sgr A* LSgrA*=2-51039 erg s-1 ~75-150 years ago Reid et al. 09

  14. Fe K emission in the GC:

  15. CS emission in the GC to locate MC TMB = 2.85 K km s-1 1.31022 cm-1 TMB = 75 K km s-1 3.41023 cm-1 nH CS= (7.51011Tex  TMB dv) /10-2 Where are the MC? Which Fe K emitter are associated to a MC? Molecular lines as tracers: MC in GC have high densities, CO auto-absorbed Uniform and complete scan of the CMZ  CS Tsuboi et al. (1999) Problems: Projection - depth in the line of sight MC velocity field not Newtonian BUT Coherent structures  similar velocities

  16. Model: wabs*(apec+edge*(PL+Ga+Ga)) the bridge Fe K+: E=6.409±0.002 keV, =28±4 eV, norm=4.7±0.310-5 ph cm-2 s-1 EW=750 eV; PL=1±0.4; nH~431022 cm-1, =0.260.12 X-ray spectra of MC G0.11-0.11 Model: wabs*(apec+edge*(PL+Ga+Ga)) Fe K+: E=6.411±0.002 keV, =28±5 eV, norm=7.5±0.510-5 ph cm-2 s-1 EW=955 eV; PL=1.9±0.4, nH~741022 cm-1, =0.030.05

  17. G0.11-0.11 3,8  4,8  Decay time ~few yr ~core light crossing time

  18. Inferring Sgr A*’s luminosity Sgr B2 NH= 81023 cm-2 Dproj= 100 pc but 130 pc in front of Sgr A* (Reid et al. 2009) Radius = 7 pc normFeK= 1.710-4 ph cm-2 s-1 L2-10 keV SgrA* ~ 1.41039 erg s-1(Revnivtsev et al. 2004) t = 100 yr Galactic plane from above Sgr A* G0.11-0.11 NH=21022 cm-2(Amo-Baladron et al. 2009) Dproj=25 pc Radius=3.7 pc normFeK=0.910-4 ph cm-2 s-1 LSgrA* > 1039 erg s-1 t > 75 years Toward the Earth Assuming FlareSgr A* = 1.41039 erg s-1 10 pc behind Sgr A* 100 yr ago

  19. Other constraints on Sgr A* activity 50 km s-1 NH=91022 cm-2 Dproj=6 pc Radius=4.7 pc normFeK<1.110-5 ph cm-2 s-1 LSgrA* < 81035 erg s-1 t < 60-90 years Galactic plane from above Toward the Earth Coil et al. (2000)

  20. The bridge Bridge 5 Bridge 6 Bridge 7 Bridge 1 11,3  9,1  2,6  8,6  13,3  Bridge 2 Bridge 3 0,8  Bridge 4 0,5  0,4 

  21. Super-luminal motion? Direction toward Sgr A* Bridge 1 Bridge 2 Bridge 3 Bridge 4 • Regions causally disconnected!! • No propagation of single event • Cosmic ray - internal source excluded! • Many un-correlated variations • Similar variation - distant source • L15pc~1.31038 erg s-1 - Binary in peculiar position close to bridge •  Flare Sgr A* (Sunyaev & Churazov 1998)

  22. How can a superluminal echo happen? Wall Projector Velocity of the variation observed on the screen = 1 m/s To change slide 1 s Wall distant 1 m from the projector

  23. How can a superluminal echo happen? Wall Projector To change slide 1 s If the wall is distant 600000 km from the projector The variation appears on the screen at v=2c! Because the real “physical” variation happens at the level of the projector and not of the wall

  24. Possible past activity of Sgr A* Galactic plane from above • Bridge • NH=91022 cm-2 • Dproj=15 pc • Radius=1.1 pc • normFeK=1.110-5 ph cm-2 s-1 • LSgrA* ~ 1.31038 erg s-1 • Assuming L~1.41039 erg s-1 • 60 pc • Sgr A* activity 400 yr Basic unknown: MC distance! Assuming a luminosity of 1039 erg s-1 MC distance Consistent with unique outburst Nothing special about 1039 erg s-1 if MC are more distant  higher Sgr A* luminosity Toward the Earth

  25. The in-glorious past of Sgr A* The projected distance between Sgr A* and MC1, MC2 and the bridge are unknown HOWEVER their physical properties indicate that they are within the CMZ (~300 pc from Sgr A) Assuming they are illuminated by Sgr A*, it is possible to pose a limit to its recent luminosity nH r d 153 pc 307 pc 460 pc 1041 Sgr A* ergs s-1 1040 • If the CMZ is filled with “similar” MC • Sgr A* never reached L>1041 ergs s-1, since the end of the Roman Empire  Sgr A* barely exited from the quiescent state, since the Romans 1039 1038

  26. Suzaku detection of Ar, Ca, Cr, Mn Kα emission Nobukawa et al. 2010 discover Kα emission from Ar, Ca, Cr and Mn in the MC X-ray spectrum Reflection: all elements consistent with ~2 Solar Cosmic electrons: consistent but ~4 Solar

  27. Can irradiation from external sources explain the emission from ALL MC? Fukuoka et al. 2009 G0.174-0.233  EW FeK = 950 eV  Reflection G0.162-0.217  EW FeK = 360 eV  LECRE

  28. Summary: Study of the past activity of Sgr A* • Observe Fe K/Gamma-ray fading of Sgr B2 • Observe another MC (G0.11-0.11) reflecting the same flare (~100 years ago) • 50 km s-1 has no Fe K line •  Sgr A* luminosity < 81035 erg s-1 in the last 60-90 years • Observe an apparent superluminal motion (in the bridge MC) •  Cosmic rays or Internal source  excluded •  the illuminating source has to be far from the arm ( >2-4 times the apparent displacement) • Sgr A* activity - best interpretation (but luminosity required is few1039 erg s-1 binary not excluded) • Kα emission lines require abundances 2 Solar MC emission consistent with a single Sgr A* period of activity of few hundreds years and lasted until ~100 years ago  As observed 1/3 of MC should be FeK bright New questions: Which is the mechanism that produces such outbursts? 106 times quiescence for >20 yr Partial stellar capture? (Yu et al. 2011) What is going to happen if Sgr A* goes to Eddington? To the GC surrounding material? To the Earth?

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