A catalogue of open cluster radii determined from Gaia proper motions

DOI: 
10.1093/mnras/staa1359
Publication date: 
01/05/2020
Main author: 
Sánchez, Néstor
IAA authors: 
Alfaro, Emilio J.
Authors: 
Sánchez, Néstor;Alfaro, Emilio J.;López-Martínez, Fátima
Journal: 
Monthly Notices of the Royal Astronomical Society
Refereed: 
Yes
Publication type: 
Article
Pages: 
2882
Abstract: 
In this work we improve a previously published method to calculate in a reliable way the radius of an open cluster. The method is based on the behaviour of stars in the proper motion space as the sampling changes in the position space. Here we describe the new version of the method and show its performance and robustness. Additionally, we apply it to a large number of open clusters using data from Gaia DR2 to generate a catalogue of 401 clusters with reliable radius estimations. The range of obtained apparent radii goes from R<SUB>c</SUB> = 1.4 ± 0.1 arcmin (for the cluster FSR 1651) to R<SUB>c</SUB> = 25.5 ± 3.5 arcmin (for NGC 2437). Cluster linear sizes follow very closely a lognormal distribution with a mean characteristic radius of R<SUB>c</SUB> = 3.7 pc, and its high radius tail can be fitted by a power law as $N \propto R_c^{-3.11\pm 0.35}$ . Additionally, we find that number of members, cluster radius and age follow the relationship $N_c \propto R_c^{1.2\pm 0.1} \cdot T_c^{-1.9\pm 0.4}$ where the younger and more extensive the cluster, the more members it presents. The proposed method is not sensitive to low density or irregular spatial distributions of stars and, therefore, is a good alternative or complementary procedure to calculate open cluster radii not having previous information on star memberships.
Database: 
ADS
URL: 
https://ui.adsabs.harvard.edu/#abs/2020MNRAS.495.2882S/abstract
ADS Bibcode: 
2020MNRAS.495.2882S
Keywords: 
catalogues;methods: data analysis;open clusters and associations: general;stars: kinematics and dynamics;Astrophysics - Astrophysics of Galaxies