The list of possible double and multiple open clusters between galactic longitudes 240 and 270 degrees

TL;DR

This study investigates the occurrence of double and multiple open clusters in the galactic sector from 240° to 270°, utilizing Gaia data to identify and analyze candidate groups, revealing that most are young and formed in groups.

Contribution

It provides an extensive list of candidate double and multiple open clusters in a specific galactic sector and uses Gaia data to validate and analyze their groupings.

Findings

Most candidate systems are less than 0.1 Gyr old.

Approximately 9.4 to 15% of known OCs are part of groups.

No older OC systems were identified.

Abstract

This work studies the candidate double and multiple open clusters (OCs) in the galactic sector from l = 240o to l = 270o, which contains the Vela-Puppis star formation region. To do that, we have searched the most recent and complete catalogues of OCs by hand to get an extensive list of 22 groups of OCs involving 80 candidate members. Gaia EDR3 has been used to review some of the candidate OCs and look for new OCs near the candidate groups. Gaia data also permitted filtering out most of the field sources that are not member stars of the OCs. The plotting of combined colour-magnitude diagrams of candidate pairs has allowed, in several cases, endorsing or discarding their link. The most likely systems are formed by OCs less than 0.1 Gyr old, with only one eccentric OC in this respect. No probable system of older OCs has been found. Preliminary estimations of the fraction of known OCs that form part of groups (9.4 to 15%) support the hypothesis that the Galaxy and the Large Magellanic Cloud are similar in this respect. The results indicate that OCs are born in groups like stars are born in OCs.