The GALAH+ Survey: A New Library of Observed Stellar Spectra Improves Radial Velocities and Hints at Motions within M67

Abstract

GALAH+ is a magnitude-limited survey of high resolution stellar spectra obtained by the HERMES spectrograph at the Australian Astronomical Observatory. Its third data release provides reduced spectra with new derivations of stellar parameters and abundances of 30 chemical elements for 584,015 dwarfs and giants, 88% of them in the Gaia magnitude range 11 < G < 14. Here we use these improved values of stellar parameters to build a library of observed spectra which is useful to study variations of individual spectral lines with stellar parameters. This and other improvements are used to derive radial velocities with uncertainties which are generally within 0.1 km/s or ~25% smaller than in the previous release. Median differences in radial velocities measured here and by the Gaia DR2 or APOGEE DR16 surveys are smaller than 30 m/s, a larger offset is present only for Gaia measurements of giant stars. We identify 4483 stars with intrinsically variable velocities and 225 stars for which the velocity stays constant over >=3 visits spanning more than a year. The combination of radial velocities from GALAH+ with distances and sky plane motions from Gaia enables studies of dynamics within streams and clusters. For example, we estimate that the open cluster M67 has a total mass of ~3300 Msun and its outer parts seem to be expanding, though astrometry with a larger time-span than currently available from Gaia eDR3 is needed to judge if the latter result is real.

arXiv comment15 pages, 4 tables, 17 figures + online data files, accepted for publication in MNRAS

References in corpus (41)

• Astropy: A Community Python Package for Astronomy
• The NumPy array: a structure for efficient numerical computation
• Gaia Data Release 2. Summary of the contents and survey properties
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• The VizieR database of Astronomical Catalogues
• The merger that led to the formation of the Milky Way's inner stellar halo and thick disk
• The New Galaxy: Signatures of its Formation
• The GALAH Survey: Scientific Motivation
• A Gaia DR2 view of the Open Cluster population in the Milky Way
• A dynamically young and perturbed Milky Way disk
• Gaia EDR3 view on Galactic globular clusters
• APOGEE Data and Spectral Analysis from SDSS Data Release 16: Seven Years of Observations Including First Results from APOGEE-South
• Streams, substructures and the early history of the Milky Way
• The GALAH Survey: Second Data Release
• The dynamical distance and intrinsic structure of the globular cluster omega Centauri
• The Stagger-grid: A Grid of 3D Stellar Atmosphere Models - I. Methods and General Properties
• Age determination for 269 $Gaia$ DR2 Open Clusters
• Gaia Radial Velocity Spectrometer
• A Complete N-body Model of the Old Open Cluster M67
• The GALAH survey and Gaia DR2: dissecting the stellar disc's phase space by age, action, chemistry and location
• New Limits on an Intermediate Mass Black Hole in Omega Centauri: II. Dynamical Models
• The GALAH Survey: Observational Overview and Gaia DR1 companion
• Gaia Data Release 2: Properties and validation of the radial velocities
• The Sixth Data Release of the Radial Velocity Experiment (RAVE) -- I: Survey Description, Spectra and Radial Velocities
• Radiative hydrodynamics simulations of red supergiant stars: I. interpretation of interferometric observations
• The TESS-HERMES survey Data Release 1: high-resolution spectroscopy of the TESS southern continuous viewing zone
• Rotation periods for cool stars in the 4 Gyr-old open cluster M67, the solar-stellar connection, and the applicability of gyrochronology to at least solar age
• Stellar Radial Velocities in the Old Open Cluster M67 (NGC 2682) I. Memberships, Binaries, and Kinematics
• Gaia Early Data Release 3: The Galactic anticentre
• The GALAH survey: The data reduction pipeline
• The K2 M67 Study: Revisiting old friends with K2 reveals oscillating red giants in the open cluster M67
• The Galah Survey: Classification and diagnostics with t-SNE reduction of spectral information
• The K2-HERMES Survey: Age and Metallicity of the Thick Disc
• The extended halo of NGC 2682 (M 67) from Gaia DR2
• The Stagger-grid: A grid of 3D stellar atmosphere models V. Synthetic stellar spectra and broad-band photometry
• The K2-HERMES Survey. I. Planet Candidate Properties from K2 Campaigns 1-3
• LAMOST Medium-Resolution Spectroscopic Survey (LAMOST-MRS): Scientific goals and survey plan
• The GALAH Survey: Accurate Radial Velocities and Library of Observed Stellar Template Spectra
• Single-lined Spectroscopic Binary Star Candidates in the RAVE Survey
• Holistic spectroscopy: Complete reconstruction of a wide-field, multi-object spectroscopic image using a photonic comb
• The GALAH survey: Multiple stars and our Galaxy. I. A comprehensive method for deriving properties of FGK binary stars

Cited by in corpus (8)

• Gaia Data Release 3 Properties and validation of the radial velocities
• Gaia Data Release 3: Catalogue Validation
• Residual Abundances in GALAH DR3: Implications for Nucleosynthesis and Identification of Unique Stellar Populations
• Characterising abundance-age relations of GALAH stars using oxygen-enhanced stellar models
• Are Lithium-Rich Giants Binaries? A Radial Velocity Variability Analysis of 1,400 Giants
• The ones that got away: chemical tagging of globular cluster-origin stars with Gaia BP/RP spectra
• Potential Impact of the Sagittarius Dwarf Galaxy on the Formation of Young O-rich Stars
• Gaia DR3 high radial velocity stars: Genuine fast-moving objects or outliers?