Expansion Kinematics of Young Clusters. I. Lambda Ori

Abstract

Context. Most stars form in clusters or associations but only a small number of these groups are expected to remain bound for longer than a few Myr. Once star formation has ended and the molecular gas around young stellar objects has been expelled via feedback processes, most initially bound young clusters lose the majority of their binding mass and begin to disperse into the Galactic field. Aims. This process can be investigated by analysing the structure and kinematic trends in nearby young clusters, particularly expansion, the tell-tale sign that a cluster is no longer gravitationally bound but is dispersing into the field. Methods. We combine Gaia DR3 5-parameter astrometry with calibrated radial velocities for members of the nearby young cluster Lambda Ori (Collinder 69). Results. We characterise the plane-of-sky substructure of the cluster using the Q-parameter and Angular Dispersion parameter. We find evidence that the cluster contains significant substructure, but that this is preferentially located away from the central cluster core, which is smooth and likely remains bound. We find strong evidence for expansion in Lambda Ori in the plane-of-sky using a number of metrics, but also that the trends are asymmetric at the 5$\sigma$ significance level. with the maximum rate of expansion being directed nearly parallel to the Galactic plane. We then invert the maximum rate of expansion of $0.144_{-0.003}^{+0.003}km{s}^{-1}p{c}^{-1}$ to give an expansion timescale of $6.944_{-0.142}^{+0.148}Myr$, which is slightly larger than typical literature age estimates for the cluster. We also find asymmetry in the velocity dispersion, potential signatures of cluster rotation, and calculate kinematic ages for individual cluster members by tracing their motion back in time to their closest approach to the cluster center.

19 pages, 17 figures, accepted A&A

References in corpus (46)

• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• Embedded Clusters in Molecular Clouds
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• A new generation of PARSEC-COLIBRI stellar isochrones including the TP-AGB phase
• A Spitzer Survey of Young Stellar Clusters within One Kiloparsec of the Sun: Cluster Core Extraction and Basic Structural Analysis
• Painting a portrait of the Galactic disc with its stellar clusters
• The Formation of a Bound Star Cluster: From the Orion Nebula Cluster to the Pleiades
• Gas expulsion and the destruction of massive young clusters
• Kinematics in Young Star Clusters and Associations with Gaia DR2
• The statistical Analysis of Star Clusters
• The APOGEE-2 Survey of the Orion Star Forming Complex II: Six-dimensional structure
• The Formation and Destruction of Molecular Clouds and Galactic Star Formation
• Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia EDR3 stars brighter than G=18.5
• Global Star Formation Rates in Disk Galaxies and Circumnuclear Starbursts from Cloud Collisions
• UPMASK: unsupervised photometric membership assignment in stellar clusters
• The Spatial Structure of Young Stellar Clusters. I. Subclusters
• The Kinematics of the Scorpius-Centaurus OB Association from Gaia DR1
• 3D mapping of young stars in the solar neighbourhood with Gaia DR2
• The SPOTS Models: A Grid of Theoretical Stellar Evolution Tracks and Isochrones For Testing The Effects of Starspots on Structure and Colors
• Dynamical traceback age of the $\beta$ Pictoris moving group
• Expanding associations in the Vela-Puppis region: 3D structure and kinematics of the young population
• OB associations and their origins
• Structure, kinematics, and ages of the young stellar populations in the Orion region
• Cygnus OB2 DANCe: A high precision proper motion study of the Cygnus OB2 association
• Survey of Surveys I: The largest catalogue of radial velocities for the Galaxy
• The Structure, Dynamics and Star Formation Rate of the Orion Nebula Cluster
• GMC Collisions as Triggers of Star Formation. III. Density and Magnetically Regulated Star Formation
• Runaway and walkaway stars from the ONC with Gaia DR2
• Asymmetrical tidal tails of open star clusters: stars crossing their cluster's prah challenge Newtonian gravitation
• The Gaia-ESO Survey: Asymmetric expansion of the Lagoon Nebula cluster NGC 6530 from GES and Gaia DR2
• Dynamical evolution of stars and gas of young embedded stellar sub-clusters
• Gaia Data Release 3 Validating the classification of variable Young Stellar Object candidates
• Unveiling the star formation history of the Upper Scorpius association through its kinematics
• Hunting for Runaways from the Orion Nebula Cluster
• SPYGLASS. III. The Fornax-Horologium Association and its Traceback History within the Austral Complex
• Age Spreads and Systematics in λ Orionis with Gaia DR2 and the SPOTS tracks
• The Structural Evolution of Forming and Early Stage Star Clusters
• The early evolution of young massive clusters: The kinematic history of NGC6611 / M16
• The dynamics of the γ Vel cluster and nearby Vela OB2 association
• Large-scale expansion of OB stars in Cygnus
• Detection of open cluster rotation fields from Gaia EDR3 proper motions
• Massive star cluster formation II. Runaway stars as fossils of sub-cluster mergers
• The Structure and 3D Kinematics of Vela OB2
• Searching for young runaways across the sky

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