Unrecognized Astrometric Confusion in the Galactic Centre

Abstract

The Galactic Centre is a highly crowded stellar field and frequent unrecognized events of source confusion, which involve undetected faint stars, are expected to introduce astrometric noise on a sub-mas level. This confusion noise is the main non-instrumental effect limiting the astrometric accuracy and precision of current near-infrared imaging observations and the long-term monitoring of individual stellar orbits in the vicinity of the central supermassive black hole. We self-consistently simulate the motions of the known and the yet unidentified stars to characterize this noise component and show that a likely consequence of source confusion is a bias in estimates of the stellar orbital elements, as well as the inferred mass and distance of the black hole, in particular if stars are being observed at small projected separations from it, such as the star S2 during pericentre passage. Furthermore, we investigate modeling the effect of source confusion as an additional noise component that is time-correlated, demonstrating a need for improved noise models to obtain trustworthy estimates of the parameters of interest (and their uncertainties) in future astrometric studies.

accepted for publication in MNRAS

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Cited by in corpus (8)

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• Detection of the Schwarzschild precession in the orbit of the star S2 near the Galactic centre massive black hole
• Improved GRAVITY astrometric accuracy from modeling of optical aberrations
• Exploring dark matter spike distribution around the Galactic centre with stellar orbits
• Observation of S4716 -- a Star with a 4 yr Orbit around Sgr A*
• A Contaminant-Free Catalogue of Gaia DR2-WISE Galactic Plane Matches: Including the Effects of Crowding in the Cross-Matching of Photometric Catalogues
• Candidate Young Stellar Objects in the S-cluster: The Kinematic Analysis of a Sub-population of the Low-mass G-objects close to Sgr A*