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Probing Strong Gravity Prague, February 18, 2010

Probing the close environment of the supermassive black hole at the center of the galaxy with GRAVITY. Probing Strong Gravity Prague, February 18, 2010. Perrin. Probing the close environment of the supermassive black hole at the center of the galaxy with GRAVITY.

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Probing Strong Gravity Prague, February 18, 2010

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  1. Probing the close environment of the supermassive black hole at the center of the galaxy with GRAVITY Probing Strong Gravity Prague, February 18, 2010 Perrin

  2. Probing the close environment of the supermassive black hole at the center of the galaxy with GRAVITY 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, Straubmeier, Thiel, Vincent, Wiest, Zanker-Smith, Ziegleder, Ziegler Probing Strong Gravity Prague, February 18, 2010

  3. Sgr A* 10 µas 2-disk central cluster (0.5 pc-12.5’’) S star cluster (12-400 mas) Circumnuclear disk (120’’) The environment of Sgr A* Mini spiral (50’’)

  4. Orbits of stars around Sgr A* Sgr A* Schödel et al. (2002)

  5. Orbits of stars around Sgr A* S2 Schödel et al. (2002)

  6. Two ways of measuring strong GRAVITY effects around Sgr A* 1. Studying the closest star orbits inside the central 60 mas Need to resolve star cluster. Scale ~ 100 Rg = 1 mas resolution. (mas) (mas) Relativistic precession in Schwarzschild metric

  7. Sgr A* blinking Genzel et al. (2003)

  8. Two ways of measuring strong GRAVITY effects around Sgr A* 2. Using flaring regions as test particles. Measure flare motion. Scale ~ 1 Rg = 10 µas accuracy Time scale = 10 min Eckart et al. A&A 500, 935 (2009) Hot spot orbiting the ISCO or a more distant orbit. Genzel et al. (2003)

  9. Sgr A* is quite dark Long wavelengths are well suited. Stars are bright in the near-infrared (orbits) and instruments sensitive enough to allow for short exposures (flares).

  10. How to get to the 1 mas resolution and 10 µas accuracy in the near-infrared ? One of Prague famous astronomers, Tycho Brahe, found the solution: use a large instrument Measurement accuracy scales as the reciprocal of the size of the instrument.

  11. Use the 4 VLT in interferometric mode Build GRAVITY ! (General Relativity viAVlt InterferomeTrY) Resolution: 3 mas @ 2.2 µm (K band) ~ 140 m

  12. Cep • Zhao et al. 2008 Altair Monnier et al. 2007 Betelgeuse Haubois et al. 2009 Mira Perrin et al. in prep Interferometric imaging in the near-infrared works Cyg • Lacour et al. 2009

  13. Imaging the closest stars with GRAVITY One-night observation image: mas mas mas mas mas Dirty 6-star image After deconvolution Point Spread Function Paumard et al. (2005)

  14. Schwarzschild advance of pericenter is detected Imaging the closest stars with GRAVITY Orbits after 15 months of observation: 1 mas = 100 Rg mas mas Paumard et al. (2005)

  15. Lens-Thirring and Quadrupole PrecessionTesting the no-hair theorem Orbital plane precession (precessionof the angular momentum vector around the spin of the black hole) 1 year orbit, e=0.9 Measurement of frame dragging precession may be feasible after a few years for orbits in the radial range between 0.2 mpc and 1 mpc (5 and 25 mas) Wheeler’s “black holes have no hair” theorem: a BH is fully characterized by only three parameters: Mass M, Spin J, Electric charge In particular Quadrupole Q2 = -J2 / M Merritt et al. (2009) Will (2008)

  16. Narrow angle interferometric astrometry Reference star Sgr A* The measured distance between the two interferograms is: Dopd= B.DS Hence: DS = Dopd/B A 5 nm accuracy on Dopd with a 100 m baseline yields a 10 µas accuracy on DS. DS opd = B.DS • Performance analysis: • errors from atmosphere, baseline, • noise, pupil position, etc … • 23 µas per baseline • 13 µas with 6 baselines opd 0

  17. The Palomar Testbed Interferometer did it ! 110 m and 87 m baselines 40 cm telescopes Muterspaugh et al. (2006): “… the 20μas level has been demonstrated …”

  18. Measuring the last stable orbit primary GR image Newton secondary GR image total image Paumard et al. (2005) See Frédéric Vincent’s talk

  19. Reference sources for GRAVITY near Sgr A* Reference source for adaptive optics Reference sources - IRS 16 - for interferometry (imaging and astrometry)

  20. Adaptive Optics Wavefront Sensor GRAVITY is in the design …

  21. … and prototyping phase Laser metrology system Fibered delay line 4-telescope integrated optics beam combiner Metrology test on VLT secondary mirror at Paranal

  22. Where we are standing and where we are going Preliminary Design Review took place in december 2009 Final Design Review is scheduled for June 2011 First tests at Paranal : 2014 Hopefully first results on Sgr A* in 5 years from now.

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