Identifying and Characterizing Stellar Clusters Toward the Galactic Anti-Center from Pan-STARRS1 Survey

The current sample of star clusters (SCs) is still incomplete beyond 1.8 kpc. The Pan-STARRS1 with its wide field of views and sensitive cameras provides us an opportunity to identify and characterize SCs as much as possible. By using a star counting algorithm, we obtained a total of 491 stellar density enhancements in a field of 20° × 20° toward the Galactic Anti-Center (GAC), of which 50 are known SCs. The remaining 441 candidates are verified with radii, interstellar reddening, distances, and ages with proper motions and multiple bands photometries. Our results push the completeness of SCs almost near the edge of GAC. With the revised SC sample, the separation between Sagittarius and Perseus arms are about 3.2 ± 0.2 kpc and the widths of the nearby spiral arms-Sagittarius, Orion, and Perseus-with are 1.4 ± 0.1, 1.6 ± 0.1, and 3.3 ± 0.2 kpc, respectively.