A catalog of newly identified star clusters in GAIA DR2

TL;DR

This paper introduces SHiP, a new pipeline for identifying star clusters in GAIA DR2 data, resulting in a catalog of 2443 candidates, including 76 newly discovered clusters, enhancing our understanding of the Galactic disk's stellar populations.

Contribution

The paper presents a novel star cluster hunting pipeline and provides a new, extensive catalog of star clusters, including newly identified candidates, improving upon previous catalogs.

Findings

Identified 2443 star cluster candidates in the Galactic disk.

Discovered 76 new star cluster candidates not listed in previous catalogs.

Most new clusters are older than log(age/yr)=8.0 and located in the inner disk.

Abstract

We present the Star cluster Hunting Pipeline (SHiP) which can identify star clusters in GAIA DR2 data, and establish a star cluster catalog for the Galactic disk. A Friend of Friend based cluster finder method is used to identify star clusters using 5-dimensional stellar parameters, $l, b, \varpi, \mu_\alpha\cos\delta$, and $\mu_\delta$. Our new catalog contains 2443 star cluster candidates identified from disk stars located within $|b|=25^\circ$ and with $G<18$ mag. An automatic isochrone fitting scheme is applied to all cluster candidates. With a combination of parameters obtained from isochrone fitting, we classify cluster candidates into three classes (Class 1, 2 and 3). Class 1 clusters are the most probable star cluster candidates with the most stringent criteria. Most of these clusters are nearby (within 4 kpc). Our catalog is cross-matched with three Galactic star cluster catalogs, Kharchenko et al. (2013), Cantat-Gaudin et al. (2018, 2019), and Bica et al. (2019). The proper motion and parallax of matched star clusters are in good agreement with these earlier catalogs. We discover 76 new star cluster candidates that are not listed in these 3 catalogs. The majority of these are clusters older than log(age/yr)=8.0, and are located in the inner disk with $|b|<5^\circ$. The recent discovery of new star clusters suggests that current Galactic star cluster catalogs are still incomplete. Among the Class 1 cluster candidates, we find 56 candidates for star cluster groups. The pipeline, the catalog and the member list containing all candidates star clusters and star cluster groups have been made publicly available.