Signature of systemic rotation in 21 Galactic Globular Clusters from APOGEE-2
Astronomy & Astrophysics(2024)
摘要
Context. Traditionally, Globular Clusters (GCs) have been assumed to be
quasi-relaxed non-rotating systems, characterized by spherical symmetry and
orbital isotropy. However, in recent years, a growing set of observational
evidence is unveiling an unexpected dynamical complexity in Galactic GCs.
Indeed, kinematic studies show that a measurable amount of internal rotation is
present in many present-day GCs. Aims. The objective of this work is to analyse
the APOGEE-2 Value-Added Catalogs (VACs) DR17 data of a sample of 21 GCs to
extend the sample showing signatures of systemic rotation, in order to better
understand the kinematic properties of GCs in general. Also, we aim to identify
the fastest rotating GC from the sample of objects with suitable measurements.
Methods. From the sample of 23 GCs included in this work, the presence of
systemic rotation was detected in 21 of the GCs, using three different methods.
All these methods use the radial velocity referred to the cluster systemic
velocity. Using the first method, it was possible to visually verify the
clear-cut signature of systemic rotation. Whereas, using the second and third
methods, it was possible to determine the amplitude of the rotation curve and
the position angle of the rotation axis. Results. This study shows that 21 GCs
have a signature of systemic rotation. For these clusters, the rotation
amplitude and the position angle of the rotation axis have been calculated. The
clusters cover a remarkable range of rotational amplitudes, from 0.77 km/s to
13.85 km/s.
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