From birth associations to field stars: mapping the small-scale orbit distribution in the Galactic disc

Abstract

Stars born at the same time in the same place should have formed from gas of the same element composition. But most stars subsequently disperse from their birth siblings, in orbit and orbital phase, becoming 'field stars'. Here we explore and provide direct observational evidence for this process in the Milky Way disc, by quantifying the probability that orbit-similarity among stars implies indistinguishable metallicity. We define the orbit similarity among stars through their distance in action-angle space, $\Delta (J,\theta )$, and their abundance similarity simply by $\Delta$[Fe/H]. Analyzing a sample of main sequence stars from Gaia DR2 and LAMOST, we find an excess of pairs with the same metallicity ($\Delta [Fe/H]<0.1$) that extends to remarkably large separations in $\Delta (J,\theta )$ that correspond to nearly 1 kpc distances. We assess the significance of this effect through a mock sample, drawn from a smooth and phase-mixed orbit distribution. Through grouping such star pairs into associations with a friend-of-friends algorithm linked by $\Delta (J,\theta )$, we find 100s of mono-abundance groups with $\ge 3$ (to $\gtrsim 20$) members; these groups -- some clusters, some spread across the sky -- are over an order-of-magnitude more abundant than expected for a smooth phase-space distribution, suggesting that we are witnessing the 'dissolution' of stellar birth associations into the field.

arXiv comment16 pages, 13 figures. Accepted for publication in MNRAS

References in corpus (63)

• Embedded Clusters in Molecular Clouds
• Gaia Data Release 2: The astrometric solution
• Local Kinematics and the Local Standard of Rest
• The Apache Point Observatory Galactic Evolution Experiment (APOGEE)
• galpy: A Python Library for Galactic Dynamics
• Stellar Multiplicity
• The New Galaxy: Signatures of its Formation
• Radial Mixing in Galactic Discs
• Global survey of star clusters in the Milky Way II. The catalogue of basic parameters
• Riding the Spiral Waves: Implications of Stellar Migration for the Properties of Galactic Disks
• Gaia Data Release 2: Mapping the Milky Way disc kinematics
• The Circular Velocity Curve of the Milky Way from $5$ to $25$ kpc
• The Cannon: A data-driven approach to stellar label determination
• Some Revised Observational Constraints on the Formation and Evolution of the Galactic Disk
• The GALAH Survey: Second Data Release
• Galaxia: a code to generate a synthetic survey of the Milky Way
• Actions for axisymmetric potentials
• The Payne: self-consistent ab initio fitting of stellar spectra
• Abundance Estimates for 16 Elements in 6 Million Stars from LAMOST DR5 Low-Resolution Spectra
• Chemical tagging with APOGEE: Discovery of a large population of N-rich stars in the inner Galaxy
• The Long-term Evolution of the Galactic Disk Traced by Dissolving Star Clusters
• Measuring Radial Orbit Migration in the Milky Way Disk
• Comoving stars in Gaia DR1: An abundance of very wide separation co-moving pairs
• Age Determinations of the Hyades, Praesepe, and Pleiades via MESA Models with Rotation
• The chemical homogeneity of open clusters
• Element abundances of unevolved stars in the open cluster M 67
• Imprints of white dwarf recoil in the separation distribution of Gaia wide binaries
• Ground-based CCD astrometry with wide field imagers. II. A star catalogue for M67: [email protected] MPG/ESO astrometry, FLAMES@VLT radial velocities
• Discovery of an equal-mass "twin" binary population reaching 1000+ AU separations
• The Galactic Disc in Action Space as seen by Gaia DR2
• Cluster Galaxy Dynamics and the Effects of Large Scale Environment
• Dynamical modeling of tidal streams
• Extended stellar systems in the solar neighborhood - II. Discovery of a nearby 120° stellar stream in Gaia DR2
• Extended distribution functions for our Galaxy
• The Hyades open cluster is chemically inhomogeneous
• Identical or fraternal twins? : The chemical homogeneity of wide binaries from Gaia DR2
• TESS reveals that the nearby Pisces-Eridanus stellar stream is only 120 Myr old
• The Separation Distribution of Ultra-Wide Binaries across Galactic Populations
• Galactic Doppelganger: The chemical similarity among field stars and among stars with a common birth origin
• Signatures of resonance and phase mixing in the Galactic disc
• The chemical compositions of solar twins in the open cluster M67
• HIPPARCOS age-metallicity relation of the solar neighbourhood disc stars
• The RAVE-on catalog of stellar atmospheric parameters and chemical abundances for chemo-dynamic studies in the Gaia era
• Testing the chemical tagging technique with open clusters
• Identifying resonances of the Galactic bar in Gaia DR2: I. Clues from action space
• Chemical tagging can work: Identification of stellar phase-space structures purely by chemical-abundance similarity
• Prospects for chemically tagging stars in the Galaxy
• How well does the Friends-of-Friends algorithm recover group properties from galaxy catalogs limited in both distance and luminosity?
• The Influence of Orbital Eccentricity on Tidal Radii of Star Clusters
• A Gaia DR2 Mock Stellar Catalog
• Prospects for Measuring Abundances of >20 Elements with Low-resolution Stellar Spectra
• Discriminating among theories of spiral structure using Gaia DR2
• Comprehensive abundance analysis of red giants in the open clusters NGC 1342, 1662, 1912, 2354 and 2447
• Stars that Move Together Were Born Together
• Blind chemical tagging with DBSCAN: prospects for spectroscopic surveys
• Constructing Polynomial Spectral Models for Stars
• Self-gravity, resonances and orbital diffusion in stellar discs
• Unbiased TGAS$\times$LAMOST distances and the role of binarity
• Machine learning in APOGEE: Identification of stellar populations through chemical abundances
• Testing the initial conditions and dynamical evolution of star clusters using Gaia - I
• The contribution of dissolving star clusters to the population of ultra-faint objects in the outer halo of the Milky Way
• The Parent Populations of 6 groups identified from Chemical Tagging in the Solar neighborhood
• Re-grouping stars based on the chemical tagging technique: A case study of M67 and IC4651

Cited by in corpus (14)

• The GALAH+ Survey: Third Data Release
• A million binaries from Gaia eDR3: sample selection and validation of Gaia parallax uncertainties
• Overview of the LAMOST survey in the first decade
• Orbital Torus Imaging: Using Element Abundances to Map Orbits and Mass in the Milky Way
• The power of co-ordinate transformations in dynamical interpretations of Galactic structure
• Chemically peculiar A and F stars with enhanced s-process and iron-peak elements: stellar radiative acceleration at work
• Disentangled Representation Learning for Astronomical Chemical Tagging
• Age-metallicity dependent stellar kinematics of the Milky Way disc from LAMOST and Gaia
• The ACTIONFINDER: An unsupervised deep learning algorithm for calculating actions and the acceleration field from a set of orbit segments
• Pearls on a String: Numerous Stellar Clusters Strung along the Same Orbit
• Spatial and Kinematic Clustering of Stars in the Galactic Disk
• Fundamental limits to orbit reconstruction due to non-conservation of stellar actions in a Milky Way-like simulation
• Evolution of action-space coherence in a Milky Way-like simulation
• Measuring chemical likeness of stars with RSCA