Julio F. Navarro

Abstract: Context. It is generally agreed upon that stars form in open clusters (OCs) and stellar associations, but little is known about structures in the Galactic OC population; whether OCs and stellar associations are born isolated or if they prefer to form in groups, for example. Answering this question provides new insight into star and cluster formation, along with a better understanding of Galactic structures.Aims. In the past decade, studies of OC groupings have either been based solely on spatial criteria or have also included tangential velocities for identifications. In contrast to previous approaches, we assumed that real OC groupings occupy a well defined area in the sky and show similar velocity vectors. For the first time, we have used 6D phase-space information, including radial velocities from the RAdial Velocity Experiment (RAVE) and other catalogues, for the detection of OC groupings. We also checked the age spread of potential candidates to distinguish between genuine groupings and chance alignments.Methods. We explored the Catalogue of Open Cluster Data (COCD) and determined 6D phase-space information for 432 out of 650 listed OCs and compact associations. The group identification was performed using an adapted version of the Friends-of-Friends algorithm, as used in cosmology, with linking lengths of 100 pc and 10–20 km s-1 . For the verification of the identified structures, we applied Monte Carlo simulations with randomised samples.Results. For the linking lengths 100 pc and 10 km s-1 , we detected 19 groupings, including 14 pairs, 4 groups with 3−5 members, and 1 complex with 15 members. The Monte Carlo simulations revealed that, in particular, the complex is most likely genuine, whereas pairs are more likely chance alignments. A closer look at the age spread of the complex and the comparison between spatial distributions of young and old cluster populations suggested that OC groupings likely originated from a common molecular cloud.

TL;DR: In this article, the satellite populations of dwarf galaxies in the Lambda$CDM were studied using the Auriga cosmological simulations of Milky Way (MW)-mass galaxies and their surroundings.

TL;DR: In this paper, a new method for the detection of double-lined binary stars in a sample of the Radial Velocity Experiment (RAVE) survey spectra is proposed, which is based on the properties and shape of the cross-correlation function, and is able to recover ~80% of all binaries with an orbital period of order 1 day.

TL;DR: In this article, the velocity anisotropy of the Milky Way (MW) satellite system was analyzed using the latest systemic proper motions for 38 satellites based on data from Gaia Data Release 2.

TL;DR: In this paper, the authors implemented a simple model to identify the likely sites of the first stars and galaxies in the high-resolution simulations of the formation of galactic dark matter halos of the Aquarius Project.