Identifying Escaped Members of Young Open Clusters

Abstract

Identifying escaped members of open clusters provides insight into how stars join the field, but this task is challenging because escaped members are vastly outnumbered by field stars. I investigated the effect of including signs of youth in membership probability calculations to determine whether this information could identify escaped members. I focused on two young clusters: α Persei, a high proper motion cluster, and IC 4665, a low proper motion cluster. Using Hierarchical Density-Based Spatial Clustering of Applications with Noise, I calculated membership probabilities including only proper motion and distance information, then repeated the calculation including color and magnitude information. In α Persei, I investigated how membership probability correlated with Hα emission with data from a 2023 survey conducted at MDM and calculated updated membership probabilities. Adding color and magnitude information promoted many low-mass stars to membership in IC 4665, but fewer stars were promoted in α Persei because PD and PDCM membership probabilities were correlated in α Persei. 85% of likely α Persei members had Hα emission, so assuming 25% of field stars are Hα emitters, adding this information raises membership probabilities. This shows adding signs of youth can identify escaped members of these clusters.No embargoAcademic Major: Astronomy and AstrophysicsAcademic Major: Physic