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The MiMO Catalog: Physical Parameters and Stellar Mass Functions of 1,232 Open Clusters from Gaia DR3

Lu Li, Zhengyi Shao, Zhaozhou Li, Xiaoting Fu

TL;DR

The paper addresses the challenge of deriving homogeneous open-cluster parameters from Gaia DR3 without stringent membership preselection. It introduces MiMO, a Bayesian mixture model that jointly fits isochrone parameters and the stellar mass function by modeling CMD densities as a mixture of cluster and field populations, with a nonparametric field component and priors informed by spectroscopy. Using this framework, the authors produce a catalog for 1,232 open clusters including ages, metallicities, distances, extinctions, and MF slopes, along with full posterior chains and photometric membership probabilities; they also designate a MF Prime subset of 163 clusters with high-quality MF estimates. The catalog, released publicly with open-source MiMO, enables precise population studies of cluster evolution and mass function variation across the Galactic disk.

Abstract

We present a homogeneous catalog of 1,232 open clusters with precisely determined ages, metallicities, distances, extinctions, and stellar mass function (MF) slopes, derived from Gaia DR3 data. The parameters are inferred using the Mixture Model for Open clusters (MiMO), a novel Bayesian framework for modeling clusters in the color-magnitude diagram. By explicitly accounting for field-star contamination as a model component, MiMO removes the conventional need for stringent membership preselection, allowing for a more complete inclusion of member stars and thereby enhancing both precision and robustness. Our results broadly agree with existing catalogs but offer improved precision. For each cluster, we provide the best-fit age, metallicity, distance, extinction, and MF slope, along with their full likelihood chains and photometric membership probabilities for individual stars. We further identify an ``MF Prime'' subsample of 163 clusters with high-quality data, for which the MF estimates are considered most reliable. The catalog and an open-source implementation of MiMO are made publicly available to the community.

The MiMO Catalog: Physical Parameters and Stellar Mass Functions of 1,232 Open Clusters from Gaia DR3

TL;DR

The paper addresses the challenge of deriving homogeneous open-cluster parameters from Gaia DR3 without stringent membership preselection. It introduces MiMO, a Bayesian mixture model that jointly fits isochrone parameters and the stellar mass function by modeling CMD densities as a mixture of cluster and field populations, with a nonparametric field component and priors informed by spectroscopy. Using this framework, the authors produce a catalog for 1,232 open clusters including ages, metallicities, distances, extinctions, and MF slopes, along with full posterior chains and photometric membership probabilities; they also designate a MF Prime subset of 163 clusters with high-quality MF estimates. The catalog, released publicly with open-source MiMO, enables precise population studies of cluster evolution and mass function variation across the Galactic disk.

Abstract

We present a homogeneous catalog of 1,232 open clusters with precisely determined ages, metallicities, distances, extinctions, and stellar mass function (MF) slopes, derived from Gaia DR3 data. The parameters are inferred using the Mixture Model for Open clusters (MiMO), a novel Bayesian framework for modeling clusters in the color-magnitude diagram. By explicitly accounting for field-star contamination as a model component, MiMO removes the conventional need for stringent membership preselection, allowing for a more complete inclusion of member stars and thereby enhancing both precision and robustness. Our results broadly agree with existing catalogs but offer improved precision. For each cluster, we provide the best-fit age, metallicity, distance, extinction, and MF slope, along with their full likelihood chains and photometric membership probabilities for individual stars. We further identify an ``MF Prime'' subsample of 163 clusters with high-quality data, for which the MF estimates are considered most reliable. The catalog and an open-source implementation of MiMO are made publicly available to the community.

Paper Structure

This paper contains 8 sections, 3 equations, 1 figure, 2 tables.

Table of Contents

  1. Introduction
  2. Method and Sample
  3. Mixture model
  4. Sample Selection
  5. Free Parameters
  6. Choice of Priors
  7. Catalog
  8. Catalog of OC Parameters

Figures (1)

  • Figure 1: Illustration of MiMO on OCs with different data quality. The color bar shows the photometric membership probability for individual stars. The left panels show high-quality clusters (named as "MF-prime") with clear and thin main sequences, while the middle panels represent typical cases with moderate main-sequence broadening. The right panels display clusters where MiMO failed to fit a reasonable isochrone due to extreme field star contamination. In each panel, grey dots represent the accessory star sample used to construct the nonparametric field-star model, and the orange line indicates the best-fit isochrone from MiMO.