New insights on the Canis Major star-forming region: an eROSITA view

The Canis Major OB1/R1 association (CMa) is a complex star-forming region hosting stellar groups aged between ~1.5 to 18 Myr and spanning over ~80 sq. deg. Its morphology, together with the presence of runaway stars, suggests that multiple supernovae (SNe) events have affected its star formation history. A comprehensive stellar population census is essential to probe whether star formation has been induced or inhibited by the SNe in the region. 

Low-mass pre-main-sequence stars are known to be X-ray emitters due to magnetic activity. Previous X-ray studies in CMa using ROSAT and XMM-Newton satellites revealed together hundreds of low-mass young stars with pointed observations. However, those observations only covered a small (~3 deg x 2 deg) portion of the association. The all-sky survey performed by the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) has made it possible to explore the whole region in X-rays.

In this work we identify optical and infrared (IR) counterparts to eROSITA soft X-ray emission among more than 3000 previously identified members and candidates of the association. By combining eROSITA data with optical and IR photometry from Gaia, 2MASS, and WISE, we characterise these objects in a multiwavelength domain. In addition, we propose new candidate members for the association based on their X-ray emission. We also made use of existing catalogues of counterparts for eROSITA sources, derived from both geometric and photometric properties (e.g., NWAY and HamStar), to support and validate our results. Our analysis provides new insights into the stellar population of CMa. They also contribute to the understanding of the evolution of stellar activity and the influence of X-ray emission in the circumstellar environment.