We use Gaia DR2 data to survey the classic Monoceros OB1 region and look for the existence of a dispersed young population, co-moving with the cloud complex. An analysis of the distribution of proper motions reveals a 20-30 Myr association of young stars, about 300-400 pc away from the far side of the Mon OB1 complex, along the same general line-of-sight. We characterize the new association, Monoceros OB4, and estimate it contains between 1400 and 2500 stars, assuming a standard IMF, putting it on par in size with NGC\,2264. We find from the internal proper motions that Mon OB4 is unbound and expanding. Our results seem to unveil a larger and more complex Monoceros star formation region, suggesting an elongated arrangement that seems to be at least 300 x 60 pc.
@article{arxiv.2103.09617,
title = {Monoceros OB4: a new association in Gaia DR2},
author = {P. S. Teixeira and J. Alves and A. Sicilia-Aguilar and A. Hacar and A. Scholz},
journal= {arXiv preprint arXiv:2103.09617},
year = {2021}
}
Comments
Accepted for publication in MNRAS Letters; 5 pages, 3 figures