Tidal Tails of Galactic Open Clusters: A Review of Methods, Evidence, and Sources of Disagreement
Abstract
Tidal tails are a natural consequence of the dynamical evolution of open clusters in the Galactic tidal field, but their observational identification is intrinsically difficult because their surface density is low and the Galactic disc contains a dense and kinematically structured field population. This review paper provides a critical synthesis of the observational and theoretical status of tidal tails of Galactic open clusters and, in particular, assesses how membership definitions, data dimensionality, clustering algorithms, and dynamical assumptions affect reported tail detections. We compare the principal approaches used with Gaia data, including convergent-point and co-moving selection, density-based clustering, probabilistic membership models, machine-learning methods, and orbit/N-body-based filtering. We compile published measurements for a representative sample of nearby clusters and explicitly distinguish robust detections from candidate or method-dependent extended structures. The literature has progressed from detailed studies of a few nearby clusters to systematic searches involving tens to hundreds of systems. The Hyades remains a benchmark because independent analyses recover coherent leading and trailing tails, but the extent and membership of the tails depend on the adopted selection. Large Gaia DR3 studies demonstrate that extended populations are common among nearby and intermediate-age clusters, while also showing that some structures can be produced or exaggerated by projection, field contamination, or the assumptions built into the membership model. Recent homogeneous analyses report tails in most of the nearby clusters in selected samples, but the corresponding catalogues should not be interpreted as equivalent because their completeness, contamination, and physical definitions of a "tail member" differ.
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BibTeX
@misc{ramezani2026tidal,
title = {{Tidal Tails of Galactic Open Clusters: A Review of Methods, Evidence, and Sources of Disagreement}},
author = {Tahereh Ramezani and Johana Balciráková and Prapti Mondal and Katerina Neumannova and Ernst Paunzen and Gabriel Szasz},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2607.13747},
eprint = {2607.13747},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.13747},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Tidal Tails of Galactic Open Clusters: A Review of Methods, Evidence, and Sources of Disagreement
AU - Tahereh Ramezani
AU - Johana Balciráková
AU - Prapti Mondal
AU - Katerina Neumannova
AU - Ernst Paunzen
AU - Gabriel Szasz
PY - 2026
DA - 2026/09/18
PB - arXiv
DO - 10.48550/arxiv.2607.13747
UR - https://arxiv.org/abs/2607.13747
AB - Tidal tails are a natural consequence of the dynamical evolution of open clusters in the Galactic tidal field, but their observational identification is intrinsically difficult because their surface density is low and the Galactic disc contains a dense and kinematically structured field population. This review paper provides a critical synthesis of the observational and theoretical status of tidal tails of Galactic open clusters and, in particular, assesses how membership definitions, data dimensionality, clustering algorithms, and dynamical assumptions affect reported tail detections. We compare the principal approaches used with Gaia data, including convergent-point and co-moving selection, density-based clustering, probabilistic membership models, machine-learning methods, and orbit/N-body-based filtering. We compile published measurements for a representative sample of nearby clusters and explicitly distinguish robust detections from candidate or method-dependent extended structures. The literature has progressed from detailed studies of a few nearby clusters to systematic searches involving tens to hundreds of systems. The Hyades remains a benchmark because independent analyses recover coherent leading and trailing tails, but the extent and membership of the tails depend on the adopted selection. Large Gaia DR3 studies demonstrate that extended populations are common among nearby and intermediate-age clusters, while also showing that some structures can be produced or exaggerated by projection, field contamination, or the assumptions built into the membership model. Recent homogeneous analyses report tails in most of the nearby clusters in selected samples, but the corresponding catalogues should not be interpreted as equivalent because their completeness, contamination, and physical definitions of a "tail member" differ.
ER -