An empirical isochrone archive for nearby open clusters

Abstract

The ages of star clusters and co-moving stellar groups contain essential information about the Milky Way. Their special properties make them excellent tracers of galactic structure and key components to unlocking its star formation history. Yet, even though the importance of stellar population ages has been widely recognized, their determination remains a challenging task often associated with highly model-dependent and uncertain results. We propose a new approach to this problem, which relies on empirical isochrones of known clusters extracted from high-quality observational data. These purely observation-based data products open up the possibility of relative age determination, free of stellar evolution model assumptions. For the derivation of the empirical isochrones, we used a combination of the statistical analysis tool principal component analysis for preprocessing and the supervised machine learning method support vector regression for curve extraction. To improve the statistical reliability of our result, we defined the empirical isochrone of a color-magnitude diagram (CMD) of a cluster as the median calculated from a set of bootstrapped curves. We provide empirical isochrones in all Gaia DR2 and DR3 color combinations for 83 nearby clusters, paving the way for a relative comparison between individual stellar populations based on an age-scaling ladder of empirical isochrones of known clusters. Due to the precision of the available observational data, we report accurate lower main sequence empirical isochrones for many clusters in our sample, which are of special interest as this region is known to be especially complex to model. We validate our results by comparing the extracted empirical isochrones to cluster ages in the literature. We also investigate the added information that empirical isochrones covering the lower main sequence can provide on two case studies.

35 pages, 26 figures

References in corpus (40)

• The NumPy array: a structure for efficient numerical computation
• The Gaia mission
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Improving PARSEC models for very low mass stars
• Painting a portrait of the Galactic disc with its stellar clusters
• The Optical to Mid-Infrared Extinction Law Based on the APOGEE, Gaia DR2, Pan-STARRS1, SDSS, APASS, 2MASS and WISE Surveys
• On the age of the $\beta$ Pictoris moving group
• Improving the open cluster census. II. An all-sky cluster catalogue with Gaia DR3
• Updated parameters of 1743 open clusters based on Gaia DR2
• Clusters and mirages: cataloguing stellar aggregates in the Milky Way
• Age determination for 269 $Gaia$ DR2 Open Clusters
• The updated BaSTI stellar evolution models and isochrones: II. alpha-enhanced calculations
• PARSEC V2.0: Stellar tracks and isochrones of low and intermediate mass stars with rotation
• Gaia Data Release 3: Apsis II -- Stellar Parameters
• The Ages of Early-Type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets
• The molecular cloud lifecycle
• Hunting for open clusters in Gaia EDR3: $628$ new open clusters found with OCfinder
• Extended stellar systems in the solar neighborhood -- V. Discovery of coronae of nearby star clusters
• Stars with Photometrically Young Gaia Luminosities Around the Solar System (SPYGLASS) I: Mapping Young Stellar Structures and their Star Formation Histories
• Extended stellar systems in the solar neighborhood - II. Discovery of a nearby 120° stellar stream in Gaia DR2
• The star formation history of the Sco-Cen association. Coherent star formation patterns in space and time
• On the Milky Way spiral arms from open clusters in Gaia EDR3
• The Seven Sisters DANCe. I. Empirical isochrones, Luminosity and Mass Functions of the Pleiades cluster
• The Gaia-ESO Survey: Empirical estimates of stellar ages from lithium equivalent widths (EAGLES)
• Significance Mode Analysis (SigMA) for hierarchical structures. An application to the Sco-Cen OB association
• The updated BaSTI stellar evolution models and isochrones. III. White Dwarfs
• Modelling unresolved binaries of open clusters in color-magnitude diagram. I. method and application of NGC3532
• SPISEA: A Python-Based Simple Stellar Population Synthesis Code for Star Clusters
• Extended stellar systems in the solar neighborhood - III. Like ships in the night: the Coma Berenices neighbor moving group
• Ruprecht 147 DANCe I. Members, empirical isochrone, luminosity and mass distributions
• Gyrochronological dating of the stellar moving group Group X
• SPYGLASS. III. The Fornax-Horologium Association and its Traceback History within the Austral Complex
• MiMO: Mixture Model for Open Clusters in Color-Magnitude Diagrams
• Robust Gaussian Process Regression Based on Iterative Trimming
• Determining the seismic age of the young open cluster $\alpha$ Per using $\delta$ Scuti stars
• SPYGLASS. II. The Multi-Generational and Multi-Origin Star Formation History of Cepheus Far North
• MADYS: the Manifold Age Determination for Young Stars
• Benchmarking Gaia DR3 Apsis with the Hyades and Pleiades open clusters
• The cosmic DANCe of Perseus I: Membership, phase-space structure, mass, and energy distributions
• Miec: A Bayesian hierarchical model for the analysis of nearby young open clusters

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• Stellar masses and mass ratios for Gaia open cluster members
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