Canis Major OB1 stellar group contents revealed by <i>Gaia</i>

Canis Major OB1 (CMa OB1) is a Galactic stellar association with very intriguing star-formation scenario. There are more than two dozen known star clusters in its line of sight, but it not clear which ones physically associated CMa OB1. We use clustering code that employs 5-dimensional data from the Gaia DR2 catalogue to identify physical groups and obtain their astrometric parameters and, addition, we different isochrone-fitting methods estimate ages these groups. find 15 distances between 570 pc 1650 pc, including 10 previously 5 new open cluster candidates. Four groups, precisely youngest ($<$ 20 Myr), CMa05, CMa06, CMa07 CMa08, confirmed be part candidate, may progenitor runaway stars. CMa06 coincides well-studied R1 star-forming region. While still forming stars, due remaining material molecular cloud Sh 2-262 nebula, CMa08 seem evolved stages evolution, no recent activity. The properties fit well monolithic scenario formation, common formation mechanism, having suffered multiple episodes formation. This suggests hierarchical model alone, explains populations other parts same association, sufficient explain whole history.