The mass distribution in the Galactic Centre from interferometric astrometry of multiple stellar orbits
Abstract
The stars orbiting the compact radio source Sgr A* in the Galactic Centre are precision probes of the gravitational field around the closest massive black hole. In addition to adaptive optics assisted astrometry (with NACO / VLT) and spectroscopy (with SINFONI / VLT, NIRC2 / Keck and GNIRS / Gemini) over three decades, since 2016/2017 we have obtained 30-100 mu-as astrometry with the four-telescope interferometric beam combiner GRAVITY / VLTI reaching a sensitivity of mK = 20 when combining data from one night. We present the simultaneous detection of several stars within the diffraction limit of a single telescope, illustrating the power of interferometry. The new data for the stars S2, S29, S38 and S55 yield significant accelerations between March and July 2021, as these stars pass the pericenters of their orbits between 2018 and 2023. This allows for a high-precision determination of the gravitational potential around Sgr A*. Our data are in excellent agreement with general relativity orbits around a single central point mass, M = 4.30 x 10^6 M_sun with a precision of about +-0.25%. We improve the significance of our detection of the Schwarzschild precession in the S2 orbit to 7 sigma. Assuming plausible density profiles, an extended mass component inside S2's apocentre (= 0.23" or 2.4 x 10^4 R_S) must be 3000 M_sun (1 sigma), or 0.1% of M. Adding the enclosed mass determinations from 13 stars orbiting Sgr A* at larger radii, the innermost radius at which the excess mass beyond Sgr A* tentatively is seen is r = 2.5" >= 10x the apocentre of S2. This is in full harmony with the stellar mass distribution (including stellar-mass black holes) obtained from the spatially resolved luminosity function.
Keywords
Cite
@article{arxiv.2112.07478,
title = {The mass distribution in the Galactic Centre from interferometric astrometry of multiple stellar orbits},
author = {GRAVITY Collaboration and R. Abuter and N. Aimar and A. Amorim and J. Ball and M. Bauböck and J. P. Berger and H. Bonnet and G. Bourdarot and W. Brandner and V. Cardoso and Y. Clénet and Y. Dallilar and R. Davies and P. T. de Zeeuw and J. Dexter and A. Drescher and F. Eisenhauer and N. M. Förster Schreiber and A. Foschi and P. Garcia and F. Gao and E. Gendron and R. Genzel and S. Gillessen and M. Habibi and X. Haubois and G. Heißel and T. Henning and S. Hippler and M. Horrobin and L. Jochum and L. Jocou and A. Kaufer and P. Kervella and S. Lacour and V. Lapeyrère and J. -B. Le Bouquin and P. Léna and D. Lutz and T. Ott and T. Paumard and K. Perraut and G. Perrin and O. Pfuhl and S. Rabien and J. Shangguan and T. Shimizu and S. Scheithauer and J. Stadler and A. W. Stephens and O. Straub and C. Straubmeier and E. Sturm and L. J. Tacconi and K. R. W. Tristram and F. Vincent and S. von Fellenberg and F. Widmann and E. Wieprecht and E. Wiezorrek and J. Woillez and S. Yazici and A. Young and G. Zins},
journal= {arXiv preprint arXiv:2112.07478},
year = {2021}
}
Comments
published in A&A