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(AO) Observations of the Galactic Center

(AO) Observations of the Galactic Center. Seth Hornstein (UCLA) CfAO Summer School on Adaptive Optics. Why Study the Galactic Center?. Is there a super massive black hole? What are the interactions of the black hole with its environment? Lensing Modified stellar formation

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(AO) Observations of the Galactic Center

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  1. (AO) Observations of the Galactic Center Seth Hornstein (UCLA) CfAO Summer School on Adaptive Optics

  2. Why Study the Galactic Center? • Is there a super massive black hole? • What are the interactions of the black hole with its environment? • Lensing • Modified stellar formation • Accretion of material CfAO Summer School on Adaptive Optics

  3. Courtesy of the Keck Observatory

  4. Courtesy of the Keck Observatory

  5. Proper Motion Studies If point mass exists, objects should follow Keplerian (elliptical) orbits Velocities yield enclosed mass as a function of radius Proof of a Black Hole CfAO Summer School on Adaptive Optics

  6. Proof of a Black Hole • High resolution is required to get to stars closest to the black hole (possibly with the shortest periods) Ghez et al., 2000 CfAO Summer School on Adaptive Optics

  7. More Proof of a Black Hole • Rschwarzschild≈3km*M For a 3x106 M black hole = 9x106km=0.05 AU!! • In order to prove there is a black hole at the Galactic Center, we must constrain the mass to a very small area. Again, this requires very high resolution. Enclosed Mass Plot Ghez et al., 1998 CfAO Summer School on Adaptive Optics

  8. Effects of the Black Hole on Its Environment • Variability • Stellar population • Accretion disk CfAO Summer School on Adaptive Optics

  9. Variability

  10. Variability • Lensing • Excellent probe of black hole mass & location. • Modified Stellar formation • How does a 2.6x106 Mobject effect formation of nearby stars? • Accretion Rate increase • Stationary variability at the position of Sgr A* could be coming from the black hole itself. CfAO Summer School on Adaptive Optics

  11. Current Work Variability CfAO Summer School on Adaptive Optics

  12. Current/Future Work High resolution spectroscopy • Previous low-res spectroscopy was able to establish the lack of CO bandhead absorption in several of the stars. • However, when looking at features intrinsic to early-type stars, it was unable to distinguish between absorption from the stellar sources and emission from background gas. Gezari et al., 2001 CfAO Summer School on Adaptive Optics

  13. Current/Future Work Proper Motion • Radial velocities & accelerations • Radial velocities will allow 3-D orbits to be fit. Thus giving estimates of both the positional location of the central dark matter and the enclosed mass. • Acceleration provides another method of confining the center of mass. Ghez et al., 2000 CfAO Summer School on Adaptive Optics

  14. Problems With Adaptive Optics at the Galactic Center • Natural guide stars are severely lacking • Keck guide star: • Very far off axis (30” from central cluster) • Dim (Vmag=13.2) • Gemini guide star: • Off axis (18” from central cluster) • Very dim (Vmag=13.8) • Anisoplanatism CfAO Summer School on Adaptive Optics

  15. Ohio State image - guide stars Courtesy of OSU (OSIRIS)

  16. Solutions • Infrared Wavefront Sensor • This would allow the use of IRS 7 as the guide star • Kmag=6.6 • Distance from GC = 6” • Laser guide star • Larger target audience. • Would be disabled by even a small amount of clouds. CfAO Summer School on Adaptive Optics

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