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Probing Relativity in the Galactic Center with Adaptive Optics Observations

This study explores the possibilities of probing relativity in the Galactic Center using adaptive optics observations. It discusses the limitations of current astrometry techniques and suggests improvements for detecting relativistic effects. The potential for detecting special and general relativistic effects in the Galactic Center is examined, with the conclusion that continued research and higher resolution imaging are worthwhile.

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Probing Relativity in the Galactic Center with Adaptive Optics Observations

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  1. The prospects of probing relativity in the Galactic Center with Adaptive Optics Observations Tobias Fritz, Stefan Gillessen, Hendrik Bartko, Katie Dodds-Eden, Frank Eisenhauer, Reinhard Genzel, Thomas Ott, Oliver Pfuhl Max-Planck-Institute for extraterrestrial physics, Garching, Germany 10 arcsec = 106 Rs

  2. Probing unprobed regimes of GR in the GC

  3. Currently: ≈30 orbits known 105Rs S2 is clearly the best star for detecting relativistic effects: The brightest one The shortest period The second closest peripassage S2 20 stars shown, Gillessen+ 2009

  4. What is limiting astrometry today? Noise induced position errors Fritz+ 2010

  5. Position scatter matches expectations compare positions in one data set divided into two, “ABAB...” Diff. Tilt Jitter PSF uncertainty Fritz+ 2010

  6. A positional noise floor: Residual Image Distortions 0.3 mas 0.15 mas NACO alignment improved Fritz+ 2010

  7. “Halo noise” Seeing halo extends beyond radii at which the PSF can be precisely determined mas • Resolution would help (ELTs) • High Strehl helps • room for improvements for PSF determination ? Fritz+ 2010

  8. S2–like stars: DistortionsFainter stars: Halo noise Fritz+ 2010

  9. How sensitive are we to relativistic effects ? Wrong: For given orbit compare Keplerian & Relativistic data Right: For given data compare Keplerian & Relativistic fit

  10. Special relativistic effects for S2 easily observable with today’s technique Zucker et al. 2006 Romer effect Transverse Doppler effect Gravitational redshift Full relativistic orbit

  11. More difficult:Measure GR pericenter shift explicitly Schwarzschild correction to 1/r potential expected: Δω = 0.22° per revolution (16 years) measured for S2: Σω = 0.84° in 18 years Rubilar & Eckart (2001), Mouawad et al. (2005), Gillessen et al. (2009)

  12. Assume, we continue what we are doing. How well do we do then? SINFONI: Spectroscopy with 15 km/s NACO: Astrometry with 300 µas

  13. 2020: 3σ detection of GR precession possible S2 only 6 positions per year 2 radial velocities per year 2 radial velocities per year, 6 per year in 2017 & 2018

  14. Special relativistic effects: highly significant for dense sampling of pericenter passage S2 only 6 positions per year 2 radial velocities per year 2 radial velocities per year, 6 per year in 2017 & 2018

  15. Summary • Limits of astrometry with 8 m telescopes: • Distortions for bright stars • Confusion/seeing halo for fainter stars • Future: • Continuing is worthwhile: • SR effects in vrad easily doable by 2020 • GR effects possible by 2020 • Big step: Higher resolution

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