Disentangling Confused Stars at the Galactic Center with Long Baseline Infrared Interferometry

Abstract

We present simulations of Keck Interferometer ASTRA and VLTI GRAVITY observations of mock star fields in orbit within ~50 milliarcseconds of Sgr A*. Dual-field phase referencing techniques, as implemented on ASTRA and planned for GRAVITY, will provide the sensitivity to observe Sgr A* with infrared interferometers. Our results show an improvement in the confusion noise limit over current astrometric surveys, opening a window to study stellar sources in the region. Since the Keck Interferometer has only a single baseline, the improvement in the confusion limit depends on source position angles. The GRAVITY instrument will yield a more compact and symmetric PSF, providing an improvement in confusion noise which will not depend as strongly on position angle. Our Keck results show the ability to characterize the star field as containing zero, few, or many bright stellar sources. We are also able to detect and track a source down to mK~18 through the least confused regions of our field of view at a precision of ~200 microarcseconds along the baseline direction. This level of precision improves with source brightness. Our GRAVITY results show the potential to detect and track multiple sources in the field. GRAVITY will perform ~10 microarcsecond astrometry on a mK=16.3 source and ~200 microarcsecond astrometry on a mK=18.8 source in six hours of monitoring a crowded field. Monitoring the orbits of several stars will provide the ability to distinguish between multiple post-Newtonian orbital effects, including those due to an extended mass distribution around Sgr A* and to low-order General Relativistic effects. Early characterizations of the field by ASTRA including the possibility of a precise source detection, could provide valuable information for future GRAVITY implementation and observation.

Accepted for publication in ApJ

References in corpus (6)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• The Two Young Star Disks in the Central Parsec of the Galaxy: Properties, Dynamics and Formation
• GRAVITY: getting to the event horizon of Sgr A*
• ASTRA: ASTrometry and phase-Referencing Astronomy on the Keck interferometer
• GRAVITY: The adaptive optics assisted, two object beam combiner for the VLTI
• First VLTI infrared spectro-interferometry on GCIRS 7 - Characterizing the prime reference source for Galactic center observations at highest angular resolution

Cited by in corpus (6)

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• Prospects for constraining the spin of the massive black hole at the Galactic center via the relativistic motion of a surrounding star
• De-Confusing blended field images using graphs and bayesian priors
• Deviation of Stellar Orbits from Test Particle Trajectories Around Sgr A* Due to Tides and Winds
• The nearby eclipsing stellar system delta Velorum - IV. Differential astrometry with VLT/NACO at the 100 microarcsecond level