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The Galaxy

GRAVITY Studying the supermassive black hole at the center of the Galaxy 46 th Rencontres de Moriond and GPHyS colloquium 2011 Gravitational Waves and Experimental Gravity Guy Perrin and the GRAVITY consortium Thursday 25 March 2011. Milky Way. Solar system. The Galaxy. Diàmeter: 25 kpc

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The Galaxy

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  1. GRAVITYStudying the supermassive black hole at the center of the Galaxy46th Rencontres de Moriond and GPHyS colloquium 2011Gravitational Waves and Experimental GravityGuy Perrin and the GRAVITY consortiumThursday 25 March 2011

  2. Milky Way Solar system The Galaxy Diàmeter: 25 kpc Spiral galaxy with bar

  3. Sgr A* 10 µas Central cluster (2 disks) (0.5 pc-12.5’’) S star cluster (12-400 mas) The environment of Sgr A* Mini spiral (50’’)

  4. The mass of Sgr A* 6 cm radio continuum emission

  5. The VLT, Very Large Telescope4 european 8 m telescopes at Cerro Paranal in Chili l/D @ 2 µm = 60 mas (600 a.u. or 0.003 pc)

  6. Adaptive Optics © Lacombe 2001 A deformable mirror compensates the errors of the incident wavefront A real-time calculator optimizes the correction The corrected wavefront leads to a good image at the diffraction limit A sensor measures residual errors

  7. Absorption toward Sgr A* is huge Av=32 Infrared observations are required

  8. Accurate mass of Sgr A*(3D orbits: imaging and spectroscopy) 3rd Kepler law: MSgr A*= 3.61±0.32 106 MSun (d = 7.62±0.32 kpc) Eisenhauer et al. (2005)

  9. 3x106 M⊙ The nature of Sgr A* Size in RS Black hole SgrA* size and motion Boson star S2 orbit Proper motions Fermion ball (17 keV) Gas motion Stellar cusp at 0.5” Nuclear Starcluster Size in pc

  10. The flaring Sgr A* Genzel et al. (2003)

  11. Flares vs. time • Central black hole activity ~ once a night • Minimum period ~ 20 minutes Genzel et al. (2003)

  12. Possible origin of flares Flare: matter is heated on a (the innernmost stable) circular orbit (30 µas if J=0) Flare period: period of the orbit Fantastic tool to study general relativity in the strong field regime. The hot spot will be used as a test particle to measure the space time around Sgr A*. Eckart et al. A&A 500, 935 (2009)

  13. Going beyond boundaries thanks to accurate spatial information • Bring the ultimate evidence that Sgr A* is a black hole: the mass is contained in the Schwarzschild radius. • Understand the nature of flares. • Use the black hole as a tool to study general relativity in the strong field regime • Study relativistic effects on nearby stars • Understand the nature of S stars and their distribution Scale ~ 1 Rs 10 µas Scale ~ 100 Rs 1 mas

  14. GRAVITY – 4 giant telescope interferometer(General Relativity viAVlt InterferomeTrY) l/B @ 2 µm = 3 mas (30 a.u. or 0.00015 pc)

  15. GRAVITY Consortium Amorim, Araujo-Hauck, Bartko, Baumeister, Berger, Brandner, Carvas, Cassaing, Chapron, Choquet, Clénet, Collin, Dodds-Eden, Eckart, Eisenhauer, Fédou, Fischer, Gendron, Genzel, Gillessen, Gräter, Hamaus, Haubois, Haug, Hippler, Hofmann, Hormuth, Houairi, Ihle, Jocou, Kellner, Kervella, Klein, Kolmeder, Lacour, Lapeyrère, Laun, Lenzen, Lima, Moratschke, Moulin, Naranjo, Neumann, Patru, Paumard, Perraut, Perrin, Pfuhl, Rabien, Ramos, Reess, Rohloff, Rousset, Sevin, Sturm, Straubmeier, Thiel, Vincent, Wiest, Zanker-Smith, Ziegleder, Ziegler

  16. Principle of the measurements with GRAVITY Reference source for infrared adaptive optics Reference sources for 10 µas astrometry and 3 mas phase reference imaging

  17. Imaging of the innermost stellar cluster(not too difficult) The central cluster (60 mas) is resolved at a scale of 3 mas = 300 Rg 1 night of observation Paumard et al. (2005) Point source response Raw image After deconvolution

  18. Imaging of the innermost stellar cluster(not too difficult) The central cluster (60 mas) is resolved at a scale of 3 mas = 300 Rg 15 months of observation Paumard et al. (2005) (mas) (mas) Relativistic precession (assuming Schwarzschild metric)

  19. No-hair theorem test(very difficult) Spinning black hole  larger precession (Lense-Thirring effect) and precession of the orbital plane (J and Q2) J Q2 GRAVITY limit after 1 year Wheeler’s no-hair theorem: a black hole is described by 3 parameters: Mass M, Spin J, Charge Quadrupolar moment Q2 = -J2 / M Will (2008)

  20. Interferometric astrometry Reference star Sgr A* Distance between two interferograms: Dopd= B DS Hence: DS = Dopd/ B With a 5 nm accuracy on Dopdand a 100 m baseline, precision on DSreaches 10 µas. A 1€ coin on the Moon as seen from Earth ! DS opd=B DS 0 opd

  21. Detecting and constraining the Innersmost Stable Circular Orbit with astrometry (very difficult) Scattering of measured positions • Expected scattering for • a 30 µas orbit • The orbit diameter • depends on J • potential • measurement of J Orbiting flare Fixed flare Vincent et al. (2010)

  22. Where do we stand now ? Concept Design Review: December 2007 Preliminary Design Review: December 2009 Final Design Review: October 2011 First tests at Paranal: 2014 Hopefully first results on Sgr A* in 4 years.

  23. Orbites d’étoiles S observées par le VLT autour de Sgr A* Sgr A* Schödel et al. (2002)

  24. Orbites d’étoiles S observées par le VLT autour de Sgr A* S2 Sgr A* Schödel et al. (2002)

  25. Sursaut calculé par Frédéric Vincent avec GYOTO(1200 h de calcul)Inclinaison de l’orbite = 70°Trou noir statique.Dernière orbite circulaire stable.Distance observateur = 50 Rs

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