Observational Evidence of Dissolving Star Clusters in M101

Joseph Converse

Advisors: Dr. Rupali Chandar, STSI
Dr. Thomas Balonek
 

Using very deep, high-resolution observations from the Hubble Space Telescope (HST) Wide Field and Planetary Camera 2 (WFPC2), we have observed the star cluster population of the nearby spiral galaxy M101.  Ages and masses for the clusters have been calculated by comparing multi-band photometry with theoretical evolutionary models.  Accurate size measurements were found by modeling point spread functions (PSFs) and using them to fit the intensity profiles to analytical King Models.  It is expected that if the star clusters are dissolving into the general galactic star population as they evolve, then the sizes should be seen to increase with age.  We find that the cluster population of M101 shows evidence of just such evolution.  We also find that the rate at which the clusters dissolve into the general galactic population is primarily dependant upon the density of the cluster.