Poster Presentation

Characterization of Star Clusters with Pan-STARRS1

Chien-Cheng Lin (SHAO, NCU), Wen-Ping Chen (NCU)

Hundreds of thousands star clusters were suggested to exist in the Galactic disk, but so far only a few thousands had been catalogued, all in the solar neighborhood (less than 2~kpc). We used PS1 3pi data with its wide-field sky and sensitive camera to search for and to characterize star clusters in the field of 20 x 20 degrees toward the Galactic anti-center. By using a star counting algorithm, we identified 491 stellar density enhancements, 50 of which were matched with known star cluster catalog. The remaining 441 candidates were characterized with radius, reddening, distance, age, and lowest mass members, along with PPMXL proper motions and 2MASS and \PS\ multi-band photometry. The revised star cluster sample was estimated to be complete up to a heliocentric distance of 5~kpc toward the Galactic anti center. Moreover, this sample allowed us to estimate the separation between Sagittarius and Perseus arms was about 3.2~kpc with 0.2~kpc uncertainty and the widths of the nearby spiral arms---Sagittarius, Orion, and Perseus-- with the full-width-half-maximum to be 1.4+\-0.1, 1.6+\-0.1, and 3.3+\-0.2~kpc, respectively.