Internal Rotation in the Globular Cluster M53

Boberg, Owen M.; Vesperini, Enrico; Friel, Eileen D.; Tiongco, Maria; Varri, Anna Lisa

doi:10.3847/1538-4357/aa7070

Cited by 30 publications

(36 citation statements)

References 42 publications

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“…The rotation present in our model is clearly evident in all projections. We wish to point out that the radial variation of the rotation axis might in some cases manifest itself as a counter-rotation of the outermost regions relative to the inner ones (see Boberg et al 2017 for a possible observational evidence of this effect). We stress, however, that a radial variation of the orientation of the rotation axis does not necessarily imply the presence of counter-rotation.…”

Section: Resultsmentioning

confidence: 99%

The complex kinematics of rotating star clusters in a tidal field

Tiongco¹,

Vesperini²,

Varri³

2018

Monthly Notices of the Royal Astronomical Society: Letters

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We broaden the investigation of the dynamical properties of tidally perturbed, rotating star clusters by relaxing the traditional assumptions of coplanarity, alignment, and synchronicity between the internal and orbital angular velocity vector of their initial conditions. We show that the interplay between the internal evolution of these systems and their interaction with the external tidal field naturally leads to the development of a number of evolutionary features in their three-dimensional velocity space, including a precession and nutation of the global rotation axis and a variation of its orientation with the distance from the cluster centre. In some cases, such a radial variation may manifest itself as a counter-rotation of the outermost regions relative to the inner ones. The projected morphology of these systems is characterized by a non-monotonic ellipticity profile and, depending on the initial inclination of the rotation axis, it may also show a twisting of the projected isodensity contours. These results provide guidance in the identification of non-trivial features which may emerge in upcoming investigations of star cluster kinematics and a dynamical framework to understand some of the complexities already hinted by recent observational studies.

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Section: Resultsmentioning

confidence: 99%

The complex kinematics of rotating star clusters in a tidal field

Tiongco¹,

Vesperini²,

Varri³

2018

Monthly Notices of the Royal Astronomical Society: Letters

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“…However, in performing such an assessment, the size and radial distribution of the sample of stars under consideration can have a significant impact. Often, all of the stars are taken into account, but previous observational and theoretical studies have shown that position angle of the rotation axis can vary as a function of the radial distance from the cluster centre (see e.g., Gebhardt et al 2000, Bianchini et al 2013, Boberg et al 2017, Tiongco et al 2018. Thus, in the case of multiple populations co-existing in a star cluster, if the populations are not yet spatially mixed, each population may also have a different position angle of its rotation axis; this effect has already been partly noted in M13 by Cordero et al (2017).…”

Section: Discussionmentioning

confidence: 99%

Kinematical evolution of multiple stellar populations in star clusters

Tiongco

Vesperini

Varri

2019

Monthly Notices of the Royal Astronomical Society

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We present the results of a suite of N-body simulations aimed at understanding the fundamental aspects of the long-term evolution of the internal kinematics of multiple stellar populations in globular clusters. Our models enable us to study the cooperative effects of internal, relaxation-driven processes and external, tidally-induced perturbations on the structural and kinematic properties of multiple-population globular clusters. To analyse the dynamical behaviour of the multiple stellar populations in a variety of spin-orbit coupling conditions, we have considered three reference cases in which the tidally perturbed star cluster rotates along an axis oriented in different directions with respect to the orbital angular momentum vector. We focus specifically on the characterisation of the evolution of the degree of differential rotation and anisotropy in the velocity space, and we quantify the process of spatial and kinematic mixing of the two populations. In light of recent and forthcoming explorations of the internal kinematics of this class of stellar systems by means of line-of sight and astrometric measurements, we also investigate the implications of projection effects and spatial distribution of the stars adopted as tracers. The kinematic and structural richness emerging from our models further emphasises the need and the importance of observational studies aimed at building a complete kinematical picture of the multiple population phenomenon.1 Although we use the terms first-and second-generation to refer to the different populations, we point out that according to some formation models (see, e.g., Bastian et al. 2013, Gieles et al. 2018) all the populations form at the same time, and in those cases the two populations are more properly referred to as first-and second-population.

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“…However, evidence of systemic rotation signatures is mounting, with the most recent results for nine GCs presented in Ferraro et al (2018a; but see also Bellazzini et al 2012;Fabricius et al 2014;Kacharov et al 2014;Kimmig et al 2015;Bellini et al 2017;Boberg et al 2017;Kamann et al 2018, and references therein). As shown by a number of theoretical studies (e.g., Fiestas et al 2006;Tiongco et al 2017; see also Figure 13), internal dynamical evolution and stellar escape cause a gradual loss of the initial cluster internal rotation.…”

Section: Discussionmentioning

confidence: 99%

“…Indeed, deviations from the sharply truncated King phase space distribution (e.g., see the cases of NGC 1851, as studied by Olszewski et al 2009;Marino et al 2014, NGC 5694 by Correnti et al 2011;Bellazzini et al 2015, and several others, as discussed, e.g., by Carballo-Bello et al 2018), spherical symmetry (e.g., Chen & Chen 2010), and pressure isotropy (e.g., van de Ven et al 2006;Bellini et al 2014Bellini et al , 2017Watkins et al 2015) are found in a growing number of GGCs. Also the observational evidence of systemic rotation is increasing (e.g., Anderson & King 2003;Lane et al 2009Lane et al , 2010Bellazzini et al 2012;Bianchini et al 2013;Fabricius et al 2014;Kacharov et al 2014;Kimmig et al 2015;Lardo et al 2015;Bellini et al 2017;Boberg et al 2017;Cordero et al 2017;Ferraro et al 2018b;Kamann et al 2018), possibly suggesting that, when properly surveyed, the majority of GCs rotate at some level. In particular, Ferraro et al (2018b) investigated the intermediate/external region of 11 clusters, demonstrating the presence of internal rotation in almost all of them.…”

Section: Introductionmentioning

confidence: 99%

The Strong Rotation of M5 (NGC 5904) as Seen from the MIKiS Survey of Galactic Globular Clusters

Lanzoni

Ferraro

Mucciarelli

et al. 2018

ApJ

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In the context of the ESO-VLT Multi-Instrument Kinematic Survey (MIKiS) of Galactic globular clusters (GGCs), we present the line-of-sight rotation curve and velocity dispersion profile of M5 (NGC 5904), as determined from the radial velocity of more than 800 individual stars observed out to 700″ (∼5 half-mass radii) from the center. We found one of the cleanest and most coherent rotation patterns ever observed for globular clusters, with a very stable rotation axis (having constant position angle of 145°at all surveyed radii) and a well-defined rotation curve. The density distribution turns out to be flattened in the direction perpendicular to the rotation axis, with a maximum ellipticity of ∼0.15. The rotation velocity peak (∼3 km s −1 in projection) is observed at ∼0.6 half-mass radii, and its ratio with respect to the central velocity dispersion (∼0.3-0.4 at 4 projected half-mass radii) indicates that ordered motions play a significant dynamical role. This result strengthens the growing empirical evidence of the kinematic complexity of GGCs and motivates the need of fundamental investigations of the role of angular momentum in collisional stellar dynamics.

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Internal Rotation in the Globular Cluster M53

Cited by 30 publications

References 42 publications

The complex kinematics of rotating star clusters in a tidal field

The complex kinematics of rotating star clusters in a tidal field

Kinematical evolution of multiple stellar populations in star clusters

The Strong Rotation of M5 (NGC 5904) as Seen from the MIKiS Survey of Galactic Globular Clusters

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