Aims. We present pyUPMASK, an unsupervised clustering method for stellar clusters that builds upon the original UPMASK package. The general approach of this method makes it plausible to be applied to analyses that deal with binary classes of any kind as long as the fundamental hypotheses are met. The code is written entirely in Python and is made available through a public repository. Methods. The core of the algorithm follows the method developed in UPMASK but introduces several key enhancements. These enhancements not only make pyUPMASK more general, they also improve its performance considerably. Results. We thoroughly tested the performance of pyUPMASK on 600 synthetic clusters affected by varying degrees of contamination by field stars. To assess the performance, we employed six different statistical metrics that measure the accuracy of probabilistic classification. Conclusions. Our results show that pyUPMASK is better performant than UPMASK for every statistical performance metric, while still managing to be many times faster.

Aims. This paper has two main objectives: (1) To determine the intrinsic properties of sixteen faint and mostly unstudied open clusters in the poorly known sector of the Galaxy at 270 • − 300 • , to probe the Milky Way structure in future investigations. (2) To address previously reported systematics in Gaia DR2 parallaxes by comparing the cluster distances derived from photometry with those derived from parallaxes. Methods. Deep UBVI photometry of 16 open clusters was carried out. Observations were reduced and analyzed in an automatic way using the ASteCA package to get individual distances, reddening, masses, ages and metallicities. Photometric distances were compared to those obtained from a Bayesian analysis of Gaia DR2 parallaxes. Results. Ten out of the sixteen clusters are true or highly probable open clusters. Two of them are quite young and follow the trace of the Carina Arm and the already detected warp. The rest of the clusters are placed in the interarm zone between the Perseus and Carina Arms as expected for older objects. We found that the cluster van den Berg-Hagen 85 is 7.5 × 10 9 yrs old becoming then one of the oldest open cluster detected in our Galaxy so far. The relationship of these ten clusters with the Galaxy structure in the solar neighborhood is discussed. The comparison of distances from photometry and parallaxes data, in turn, reveals a variable level of disagreement. Conclusions. Various zero point corrections for Gaia DR2 parallax data recently reported were considered for a comparison between photometric and parallax based distances. The results tend to improve with some of these corrections. Photometric distance analysis suggest an average correction of ∼+0.026 mas (to be added to the parallaxes). The correction may have a more intricate distance dependency, but addressing that level of detail will require a larger cluster sample.

Context. 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 then employed in larger scale analyses, for example the structure of the Galaxy’s spiral arms. The distance is one of the most 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 kiloparsecs away. Aims. We cross-matched several published catalogs and selected the 25 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 the catalogs and our estimates. Methods. Photometric and astrometric data from the Gaia EDR3 survey was employed. The data were processed with our own membership analysis code, pyUPMASK, and our package for the automatic estimation of fundamental cluster parameters, ASteCA. Results. We find differences in the estimated distances of up to several kiloparsecs between our results and those cataloged, even for the catalogs that show the best matches with 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 cataloged to date. Conclusions. Caution is thus strongly recommended when using cataloged parameters of open clusters to infer large-scale properties of the Galaxy, particularly for those located more than a few kiloparsecs away.