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Gaia DR3 Analysis of Four Open Clusters Toward the Galactic Anticenter

Selçuk Bilir, Seval Taşdemir, Ege Eraydın, Deniz Cennet Çınar, Jeison Alfonso, Remziye Canbay

Abstract

This study provides a detailed examination of the structural, astrophysical, kinematic, and dynamical properties of the open clusters COIN-Gaia 24, Czernik 24, FSR 0893, and UBC 74, which are located in the direction opposite to the Galactic center. Astrometric, photometric, and spectroscopic data from the Gaia Data Release 3 catalog were used to ensure a precise characterization of cluster members and their physical properties. Membership determination was performed using the UPMASK algorithm applied to a five-dimensional parameter space, yielding 116, 179, 238, and 387 likely members for each cluster, respectively. Structural parameters were derived by fitting King profiles to the radial density distributions of high-probability members. Astrophysical parameters were estimated through Bayesian Markov Chain Monte Carlo isochrone fitting based on PARSEC evolutionary models, complemented by spectral energy distribution analysis using ARIADNE. The resulting extinctions, distances, metallicities, and ages indicate that these are moderately reddened, intermediate-age clusters located between 1 and 3.5 kpc from the Sun. Mean radial velocities combined with Galactic orbital integrations computed with galpy show that all four clusters follow nearly circular, low-eccentricity orbits typical of thin-disc populations. All four OCs have dynamical relaxation times of 22-98 Myr. However, their ages exceed these times by several factors, particularly in Czernik 24, indicating that they are dynamically evolved systems, even though the calculated T_E values represent lower limits. The results confirm that these OCs serve as reliable tracers of the chemical and dynamical evolution of the Galactic thin disc.

Gaia DR3 Analysis of Four Open Clusters Toward the Galactic Anticenter

Abstract

This study provides a detailed examination of the structural, astrophysical, kinematic, and dynamical properties of the open clusters COIN-Gaia 24, Czernik 24, FSR 0893, and UBC 74, which are located in the direction opposite to the Galactic center. Astrometric, photometric, and spectroscopic data from the Gaia Data Release 3 catalog were used to ensure a precise characterization of cluster members and their physical properties. Membership determination was performed using the UPMASK algorithm applied to a five-dimensional parameter space, yielding 116, 179, 238, and 387 likely members for each cluster, respectively. Structural parameters were derived by fitting King profiles to the radial density distributions of high-probability members. Astrophysical parameters were estimated through Bayesian Markov Chain Monte Carlo isochrone fitting based on PARSEC evolutionary models, complemented by spectral energy distribution analysis using ARIADNE. The resulting extinctions, distances, metallicities, and ages indicate that these are moderately reddened, intermediate-age clusters located between 1 and 3.5 kpc from the Sun. Mean radial velocities combined with Galactic orbital integrations computed with galpy show that all four clusters follow nearly circular, low-eccentricity orbits typical of thin-disc populations. All four OCs have dynamical relaxation times of 22-98 Myr. However, their ages exceed these times by several factors, particularly in Czernik 24, indicating that they are dynamically evolved systems, even though the calculated T_E values represent lower limits. The results confirm that these OCs serve as reliable tracers of the chemical and dynamical evolution of the Galactic thin disc.
Paper Structure (18 sections, 12 equations, 18 figures, 8 tables)

This paper contains 18 sections, 12 equations, 18 figures, 8 tables.

Table of Contents

  1. Introduction
  2. Data analysis
  3. Photometric Data
  4. Determination of the Cluster Center
  5. Photometric Completeness Limit
  6. Membership Determination
  7. Determining the structural parameters
  8. Astrophysical Parameters of the Clusters
  9. Bayesian Inference of Cluster Parameters Using MCMC
  10. Spectral Energy Distribution Analysis
  11. Variability, Multiplicity, and Evolutionary Status of Member Stars
  12. Variables and Binaries
  13. Blue Straggler Stars
  14. Kinematic and Orbital analysis
  15. Investigating the Dynamical Behavior of the Clusters
  16. ...and 3 more sections

Figures (18)

  • Figure 1: Projected spatial distribution of the four OCs on the Galactic plane, with the Sun at 8 kpc from the center and each OC shown as a red dot in the Galactic anti-center region.
  • Figure 2: $40\times40$ arcmin$^{2}$ star fields for selected OCs in the equatorial coordinate system. North and east correspond to the up and left directions, respectively.
  • Figure 3: The two-dimensional stellar density maps of the four OCs. The top panel of the density maps shows the histogram for right ascension ($\alpha$), and the right panel shows the histogram for declination ($\delta$). The solid lines represent the Gaussian curves fitted to the histograms.
  • Figure 4: Observed (blue) and model (red) stellar count histograms in the $G$-band for the four OCs. The black dashed lines indicate the photometric completeness limits.
  • Figure 5: The cluster membership probability of stars in the four OC directions.
  • ...and 13 more figures