A Galactic Interloper: A Study of the Cam OB1 Association's Clusters and its Visitor from the Perseus Arm

TL;DR

This study uses Gaia data to identify and analyze three distinct star clusters within the Cam OB1 association, revealing their origins, ages, and the fact that they can pass through each other while traveling through the Galaxy.

Contribution

First detailed analysis of the 3D structure, motion, and origins of clusters in the Cam OB1 region using Gaia astrometry and radial velocities.

Findings

Identified three clusters with ages 10, 15.8, and 20 Myr.

Clusters originated in different regions, some from the Perseus arm.

Clusters currently overlap in 3D space, passing through each other.

Abstract

Within the molecular clouds of the Camelopardis 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 ($137 \lessapprox l\lessapprox145$ and $-2\lessapprox b \lessapprox5$) and at a similar distance ($\sim$1kpc). 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 SDSS-V radial velocities, we find the 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 location, 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 Per OB1 or Cas 0B6 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.