| Issue |
A&A
Volume 683, March 2024
|
|
|---|---|---|
| Article Number | A150 | |
| Number of page(s) | 6 | |
| Section | Galactic structure, stellar clusters and populations | |
| DOI | https://doi.org/10.1051/0004-6361/202348100 | |
| Published online | 15 March 2024 | |
The globular cluster VVV CL002 falling down to the hazardous Galactic centre
1
Instituto de Astrofísica, Depto. de Ciencias Físicas, Facultad de Ciencias Exactas, Universidad Andres Bello, Fernandez Concha 700, Santiago, RM, Chile
e-mail: dante.minniti@unab.cl
2
Specola Vaticana, Vatican Observatory, Castelgandolfo, V00120 Stato Citta Vaticano, Italy
3
Departamento de Fisica, Universidade Federal de Santa Catarina, Florianopolis, Trindade, 88040-900 SC, Brazil
4
Department of Astronomy, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
e-mail: matsunaga@astron.s.u-tokyo.ac.jp
5
Laboratory of Infrared High-resolution Spectroscopy (LiH), Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan
6
Instituto de Astronomía, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta, Chile
7
National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
8
Photocoding, 460-102 Iwakura-Nakamachi, Sakyo-ku, Kyoto 606-0025, Japan
9
Department of Astrophysics and Atmospheric Sciences, Faculty of Science, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan
10
Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9A, UK
11
Institute of Astronomy, University of Cambridge, Madingley Rd., Cambridge CB3 0HA, UK
12
Centro de Astronomia (CITEVA), Universidad de Antofagasta, Av. Angamos 601, Antofagasta, Chile
13
INAF, Osservatorio Astronomico di Roma, Via di Frascati 33, Monteporzio Catone 00040, Italy
Received:
28
September
2023
Accepted:
11
December
2023
Context. The Galactic centre is hazardous for stellar clusters because of the strong tidal force in action there. It is believed that many clusters were destroyed there and contributed stars to the crowded stellar field of the bulge and the nuclear stellar cluster. However, the development of a realistic model to predict the long-term evolution of the complex inner Galaxy has proven difficult, and observations of surviving clusters in the central region would provide crucial insights into destruction processes.
Aims. Among the known Galactic globular clusters, VVV CL002 is the closest to the centre, at 0.4 kpc, but has a very high transverse velocity of 400 km s−1. The nature of this cluster and its impact on Galactic astronomy need to be addressed with spectroscopic follow up.
Methods. Here we report the first measurements of its radial velocity and chemical abundance based on near-infrared high-resolution spectroscopy.
Results. We find that this cluster has a counter-rotating orbit constrained within 1.0 kpc of the centre, and as close as 0.2 kpc at the perigalacticon, confirming that the cluster is not a passerby from the halo but a genuine survivor enduring the harsh conditions of the tidal forces of the Galactic mill. In addition, its metallicity and α abundance ([α/Fe] ≃ +0.4 and [Fe/H] = −0.54) are similar to those of some globular clusters in the bulge. Recent studies suggest that stars with such α-enhanced stars were more common at 3–6 kpc from the centre around 10 Gyr ago.
Conclusions. We infer that VVV CL002 was formed outside but is currently falling down to the centre, showcasing a real-time event that must have occurred to many clusters a long time ago.
Key words: stars: abundances / globular clusters: general / Galaxy: nucleus
© The Authors 2024
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.
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