A Galactic Interloper: A Study of the Camelopardis OB1 Association’s Clusters and Its Visitor from the Perseus Arm

Journal article, 2025

Within the molecular clouds of the Camelopardis OB1 (Cam OB1) association exists a region previously noted as one subgroup. However, bulk clustering from Gaia astrometry has recently shown three distinctive kinematically coherent groups, all found in a similar location in the sky (137 ⪅ l ⪅ 145 and −2 ⪅ b ⪅ 5) and at a similar distance (∼1 kpc). In this work, we derive from first principles the three proposed clusters in this region, refine the membership list and cluster ages, and, for the first time, examine the 3D structure, motion, and origin of the clusters. Using clustering of Gaia data in 3D position + 2D velocity space, supplemented by available fifth-generation Sloan Digital Sky Survey radial velocities, we find clusters of ages 10, 15.8, and 20 Myr with members numbering 140, 469, and 184, respectively. All three clusters overlap currently in 3D space. Tracing their previous locations, based on present-day motions, shows that each cluster originated in its own distinct region and exhibited no influence on each other’s formation. Two of the clusters trace their origin to different areas within the Cam OB1 association, with the oldest cluster tracing its origins to the near edge of the Perseus Arm, in the direction of the Perseus OB1 or Cassiopeia OB6 associations. Overall, this work illustrates how different stellar groups, even those originating in a different spiral arm, can visit and pass through each other as they travel through the Galaxy.