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arXiv · 1509.01941

Pinpointing the near-infrared location of Sgr A* by correcting optical distortion in the NACO imager

P. M. Plewa·S. Gillessen·F. Eisenhauer·T. Ott·O. Pfuhl·E. George·J. Dexter·M. Habibi·R. Genzel·M. J. Reid·K. M. Menten
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Abstract

Near-infrared observations of stellar orbits at the Galactic Center provide conclusive evidence for a massive black hole associated with the compact radio source Sgr A*. The astrometric reference frame for these observations is tied to a set of red giant stars, which are also detectable at radio wavelengths through SiO maser emission in their envelopes. We have improved the precision and long-term stability of this reference frame, in which Sgr A* is localized to within a factor 5 better than previously: ~0.17 mas in position (in 2009) and ~0.07 mas/yr in velocity. This improvement is the result of modeling and correcting optical distortion in the VLT/NACO imager to a sub-mas level and including new infrared and radio measurements, which now both span more than a decade in time. A further improvement will follow future observations and facilitate the detection of relativistic orbital effects.

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P. M. Plewa, S. Gillessen, F. Eisenhauer, T. Ott, O. Pfuhl, E. George, J. Dexter, M. Habibi, R. Genzel, M. J. Reid, K. M. Menten. 2015-09-07. Pinpointing the near-infrared location of Sgr A* by correcting optical distortion in the NACO imager. https://doi.org/10.1093/mnras%2Fstv1910

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