The morphological stability of open clusters: a new 2D perspective

Abstract

Open clusters (OCs) usually evolve gradually as the number of their members changes, which can be manifested in their morphological characteristics. We aim to investigate the morphological stability of 1,490 OCs and further explore the potential change of morphological stability of the OCs at different spatial positions, using the OC catalog from the literature. We define for the first time a new morphological stability parameter Ncore/Nouter, a ratio of member numbers between cluster core and outer areas within tidal radii, which has a significant positive correlation against N, with a slope of 1.140$\pm$0.039, significantly steeper than the 0.720$\pm$0.026 measured for Score/Souter. This demonstrates that the stellar density in the core is a more sensitive tracer for morphological stability than geometry. Spatially, the radial sample OCs have larger slopes of Ncore/Nouter and Score/Souter against N, with 1.083$\pm$0.116 and 0.733$\pm$0.080, respectively, whereas those in the tangential direction 1.013$\pm$0.110 and 0.529$\pm$0.075, respectively, which means that the impact on sample OCs from tidal forces directed toward the Galactic center is possibly stronger than that from the shear force caused by the differential rotation of the Galactic disk. Besides, the sample OCs younger than 30 Myr display a shallow slope of 0.751$\pm$0.166, with those older than 800 Myr (1.442$\pm$0.128), reflecting that young OCs likely endure both internal disruptions, such as early dynamical heating weakening core binding and more severe external disturbances, compared to older OCs.

17 pages, 23 figures, 5 tables, accepted for publication in A&A

References in corpus (55)

• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The Gaia mission
• Gaia Data Release 3: Summary of the content and survey properties
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Embedded Clusters in Molecular Clouds
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• Young massive star clusters
• Trigonometric Parallaxes Of High-Mass Star Forming Regions: Our View Of The Milky Way
• Gaia Data Release 2: using Gaia parallaxes
• Star Clusters Across Cosmic Time
• Estimating distances from parallaxes
• Data analysis recipes: Using Markov Chain Monte Carlo
• Revisiting the population of Galactic open clusters
• Improving the open cluster census. III. Using cluster masses, radii, and dynamics to create a cleaned open cluster catalogue
• The Spitzer Space Telescope Survey of the Orion A and B Molecular Clouds II: the Spatial Distribution and Demographics of Dusty Young Stellar Objects
• Variations in Stellar Clustering with Environment: Dispersed Star Formation and the Origin of Faint Fuzzies
• Red giants observed by CoRoT and APOGEE: The evolution of the Milky Way's radial metallicity gradient
• 3D kinematics and age distribution of the Open Cluster population
• Extended stellar systems in the solar neighborhood - I. The tidal tails of the Hyades
• IN-SYNC II: Virial Stars from Sub-Virial Cores -- The Velocity Dispersion of Embedded Pre-Main-Sequence Stars in NGC 1333
• Orion Revisited - I. The massive cluster in front of the Orion Nebula Cluster
• Discovery of Tidal Tails in Disrupting Open Clusters: Coma Berenices and a Neighbor Stellar Group
• 3D Morphology of Open Clusters in the Solar Neighborhood with Gaia EDR3: its Relation to Cluster Dynamics
• The extended halo of NGC 2682 (M 67) from Gaia DR2
• Gravitational tidal effects on galactic open clusters
• Evolution of the local spiral structure of the Milky Way revealed by open clusters
• 3D Morphology of Open Clusters in the Solar Neighborhood with Gaia EDR3 II: Hierarchical Star Formation Revealed by Spatial and Kinematic Substructures
• From the Top Down and Back Up Again: Star Cluster Structure from Hierarchical Star Formation
• Structural and dynamical modeling of WINGS clusters. II. The orbital anisotropies of elliptical, spiral and lenticular galaxies
• New insights into the structure of open clusters in the Gaia era
• Simulations predict intermediate-mass black hole formation in globular clusters
• A machine learning-based tool for open cluster membership determination in Gaia DR3
• Open-cluster density profiles derived using a kernel estimator
• First phase space portrait of a hierarchical stellar structure in the Milky Way
• Clusterix 2.0. A Virtual Observatory tool to estimate cluster membership probability
• Towards a census of the Galactic anticentre star clusters II: exploring lower overdensities
• Ongoing hierarchical massive cluster assembly: the LISCA II structure in the Perseus complex
• Deciphering Star Cluster Evolution by Shape Morphology
• Decoding the Morphological Evolution of Open Clusters
• On the Dispersal of Young Stellar Hierarchies
• The tangled warp of the Milky Way
• Global properties, fractality, and mass segregation in single, paired, and grouped open clusters
• Galactic warps: from cosmic noon to the current epoch
• Exploring Galactic open clusters with Gaia I. An examination in the first kiloparsec
• Modelling the evolution of the Galactic disc scale height traced by open clusters
• Open cluster dissolution rate and the initial cluster mass function in the solar neighbourhood. Modelling the age and mass distributions of clusters observed by Gaia
• Nearby open clusters with tidal features: golden sample selection and 3D structure
• A detection of the layered structure of nearby open clusters
• Sloshing and spiral structures breeding a putative radio mini-halo in the environment of a cool-core cluster Abell 795
• Exploration of morphological coherence in open clusters with a "core-shell'' structure
• Metallicities of old open clusters: A new Galactic map
• Galactic bars are already mature at Cosmic Noon: bar strength and flatness at z ~ 1.5
• Azimuthal Misalignments in Stellar Warp Structure as Dynamical Tracers of Mergers in Milky Way-like Galaxies
• Fractality of open clusters in singles, pairs, and groups