On the assessment of the nature of open star clusters and the determination of their basic parameters with limited data

Abstract

Our knowledge of stellar evolution and of the structure and chemical evolution of the Galactic disk largely builds on the study of open star clusters. Because of their crucial role in these relevant topics, large homogeneous catalogues of open cluster parameters are highly desirable. Although efforts have been made to develop automatic tools to analyse large numbers of clusters, the results obtained so far vary from study to study, and sometimes are very contradictory when compared to dedicated studies of individual clusters. In this work we highlight the common causes of these discrepancies for some open clusters, and show that at present dedicated studies yield a much better assessment of the nature of star clusters, even in the absence of ideal data-sets. We make use of deep, widefield, multi-colour photometry to discuss the nature of six strategically selected open star clusters: Trumpler 22, Lynga 6, Hogg 19, Hogg 21, Pismis 10 and Pismis 14. We have precisely derived their basic parameters by means of a combination of star counts and photometric diagrams. Trumpler 22 and Lynga 6 are included in our study because they are widely known, and thus provided a check of our data and methodology. The remaining four clusters are very poorly known, and

Effect of Binarity in Star Cluster Dynamical Mass Determination

“…Moreover, open clusters contain fractions of binaries larger than the globular cluster (de la Fuente Marcos & de la Fuente Marcos 2008; Carraro et al 2017), and are widely accepted to be devoid of dark matter halos. The small number of stars belonging to open clusters allows a tight comparison with numerical models.…”

New atlas of open star clusters

“…Publications with newly found clusters are going on, for example, Loktin and Popova (2017) found 48 new possible candidates. Some objects are shown not to be real clusters after detailed investigations (for example, Pismis 14 in Carraro et al (2017), and ESO131SC09, NGC 5284 and vdBergh-Hagen 164 in Carraro and Seleznev (2012)). It is necessary to find all double mentionings of the same cluster with different names.…”

Astrophysical Parameters of the Open Cluster Berkeley 6

“…Moreover, the fitting procedure gives the age and distance moduli of Be 6 to be t = 350±50 Myr and (m-MG) = 13.806±0.263 mag, respectively, which corresponds to the isochrone distance to be diso= 2625±337 pc (see Table 3). In addition to this, we calculated errors in distance moduli and distances using the relations presented in [22], [24], [25], [26]. These relations take into account the uncertainty in colour excess.…”