Nine tiny star clusters in Gaia DR1, PS1 and DES

TL;DR

This paper reports the discovery of nine new compact stellar systems in the Milky Way using data from Gaia, DES, and Pan-STARRS, expanding the known parameter space of star clusters and suggesting a continuum between open and globular clusters.

Contribution

It introduces a systematic search method across multiple surveys for small, faint stellar systems, revealing new objects and challenging the traditional classification of star clusters.

Findings

Discovered 9 new compact stellar systems.

Extended the known size and luminosity range of star clusters.

Suggested a continuum between open and globular clusters.

Abstract

We present the results of a systematic Milky Way satellite search performed across an array of publicly available wide-area photometric surveys. Our aim is to complement previous searches by widening the parameter space covered. Specifically, we focus on objects smaller than $1'$ and include old, young, metal poor and metal rich stellar population masks. As a result we find 9 new likely genuine stellar systems in data from GAIA, DES, and Pan-STARRS, which were picked from the candidate list because of conspicuous counterparts in the cut-out images. The presented systems are all very compact ($r_h<1'$) and faint ($M_V\gtrsim-3$), and are associated either with the Galactic disk, or the Magellanic Clouds. While most of the stellar systems look like Open Clusters, their exact classification is, as of today, unclear. With these discoveries, we extend the parameter space occupied by star clusters to sizes and luminosities previously unexplored and demonstrate that rather than two distinct classes of Globular and Open clusters, there appears to be a continuity of objects, unmarked by a clear decision boundary.