An analysis of the most distant catalogued open clusters -- Re-assessing fundamental parameters with Gaia EDR3 and $\texttt{ASteCA}$

TL;DR

This study re-evaluates fundamental parameters of the most distant open clusters using Gaia EDR3 data and the ASteCA tool, revealing significant discrepancies in distance and age estimates across catalogs, and identifying vd Bergh-Hagen 176 as potentially the most distant known open cluster.

Contribution

It provides a detailed re-analysis of distant open clusters' parameters, highlighting inconsistencies in existing catalog data and demonstrating the importance of precise methods like ASteCA.

Findings

Significant differences in distance estimates up to several kpc.

Large discrepancies in age determinations.

vd Bergh-Hagen 176 may be the most distant catalogued open cluster.

Abstract

Several studies have been presented in the last few years applying some kind of automatic processing of data to estimate the fundamental parameters of open clusters. These parameters are later on employed in larger scale analyses, for example the structure of the Galaxy's spiral arms. The distance is one of the more straightforward parameters to estimate, yet enormous differences can still be found among published data. This is particularly true for open clusters located more than a few kpc away. We cross-matched several published catalogues and selected the twenty-five most distant open clusters ($>$9000 pc). We then performed a detailed analysis of their fundamental parameters, with emphasis on their distances, to determine the agreement between catalogues and our estimates.} Photometric and astrometric data from the Gaia EDR3 survey was employed. The data was processed with our own membership analysis code (pyUPMASK), and our package for automatic fundamental cluster's parameters estimation ($\texttt{ASteCA}$). We find differences in the estimated distances of up to several kpc between our results and those catalogued, even for the catalogues that show the best matches with $\texttt{ASteCA}$ values. Large differences are also found for the age estimates. As a by-product of the analysis we find that vd Bergh-Hagen 176 could be the open cluster with the largest heliocentric distance catalogued to date. Caution is thus strongly recommended when using catalogued parameters of open clusters to infer large-scale properties of the Galaxy, particularly for those located more than a few kpc away.