Issue |
A&A
Volume 672, April 2023
|
|
---|---|---|
Article Number | A63 | |
Number of page(s) | 11 | |
Section | Galactic structure, stellar clusters and populations | |
DOI | https://doi.org/10.1051/0004-6361/202245132 | |
Published online | 31 March 2023 |
Where intermediate-mass black holes could hide in the Galactic Centre
A full parameter study with the S2 orbit
1
Max Planck Institute for Extraterrestrial Physics, Giessenbachstraße 1, 85748 Garching, Germany
2
ORIGINS Excellence Cluster, Boltzmannstraße 2, 85748 Garching, Germany
3
Department of Physics, University of Illinois, 1110 West Green Street, Urbana, IL 61801, USA
4
European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
5
LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, 92195 Meudon, France
6
Universidade de Lisboa – Faculdade de Ciências, Campo Grande, 1749-016 Lisboa, Portugal
7
CENTRA – Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal
8
Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
9
Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
10
Universidade do Porto, Faculdade de Engenharia, Rua Dr. Roberto, Frias, 4200-465 Porto, Portugal
11
Department of Astrophysical & Planetary Sciences, JILA, University of Colorado, Duane Physics Bldg., 2000 Colorado Ave, Boulder, CO 80309, USA
12
Faculdade de Engenharia, Universidade do Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
13
Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany
14
Departments of Physics and Astronomy, Le Conte Hall, University of California, Berkeley, CA 94720, USA
15
European Southern Observatory, Casilla, 19001 Santiago 19, Chile
16
Max Planck Institute for Astrophysics, Karl-Schwarzschild-Straße 1, 85748 Garching, Germany
17
Institute of Physics, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
18
Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany
19
Institute of Multidisciplinary Mathematics, UPV, Camino de Vera, s/n 46022 Valencia, Spain
20
Kavli Institute for Astronomy and Astrophysics, Peking University, 5 Yiheyuan Rd, Haidian, Beijing 100871, PR China
21
Advanced Concepts Team, European Space Agency, TEC-SF, ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
22
Niels Bohr International Academy, Niels Bohr Institute, Blegdamsvej 17, 2100 Copenhagen, Denmark
Received:
4
October
2022
Accepted:
16
February
2023
Context. In the Milky Way the central massive black hole, Sgr A*, coexists with a compact nuclear star cluster that contains a sub-parsec concentration of fast-moving young stars called S-stars. Their location and age are not easily explained by current star formation models, and in several scenarios the presence of an intermediate-mass black hole (IMBH) has been invoked.
Aims. We use GRAVITY astrometric and SINFONI, KECK, and GNIRS spectroscopic data of S2, the best known S-star, to investigate whether a second massive object could be present deep in the Galactic Centre (GC) in the form of an IMBH binary companion to Sgr A*.
Methods. To solve the three-body problem, we used a post-Newtonian framework and consider two types of settings: (i) a hierarchical set-up where the star S2 orbits the Sgr A*–IMBH binary and (ii) a non-hierarchical set-up where the IMBH trajectory lies outside the S2 orbit. In both cases we explore the full 20-dimensional parameter space by employing a Bayesian dynamic nested sampling method.
Results. For the hierarchical case we find the strongest constraints: IMBH masses > 2000 M⊙ on orbits with smaller semi-major axes than S2 are largely excluded. For the non-hierarchical case, the chaotic nature of the problem becomes significant: the parameter space contains several pockets of valid IMBH solutions. However, a closer analysis of their impact on the resident stars reveals that IMBHs on semi-major axes larger than S2 tend to disrupt the S-star cluster in less than a million years. This makes the existence of an IMBH among the S-stars highly unlikely.
Conclusions. The current S2 data do not formally require the presence of an IMBH. If an IMBH hides in the GC, it has to be either a low-mass IMBH inside the S2 orbit that moves on a short and significantly inclined trajectory or an IMBH with a semi-major axis > 1″. We provide the parameter maps of valid IMBH solutions in the GC and discuss the general structure of our results and how future observations can help to put even stronger constraints on the properties of IMBHs in the GC.
Key words: black hole physics / gravitation / Galaxy: center / Galaxy: nucleus / Galaxy: kinematics and dynamics / Galaxy: structure
Note to the reader: affiliations have been corrected on 7 April 2023.
Note to the reader: S. Yazici was mistakenly included as a co-author without his knowledge. Following the publication of the corrigendum, his name was deleted on 20 September 2023.
© The Authors 2023
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model.
Open Access funding provided by Max Planck Society.
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