Dynamical Substructures of Galactic Globular Clusters I. M5

Abstract

CCD images to study the dynamical substructure of the globular cluster M5. We investigate the radial variation of ellipticities and position angles using the stellar photometry and the IRAF ellipse task. We find that out to three times the half light radius (rh), the changes in ellipticities and position angles range in 0.05˜0.25 and 75° ˜ -75°, respectively. There are no significant discrepancy in the dynamical substructure beyond rh among the different giant populations. However, compared to the global dynamical substructure of M5, the inner (<0.5 rh) substructure of the bright red giant and the horizontal branch populations show slightly different patterns. Especially, the discrepancy of the bright red giant population with respect to the global substructure, ranges up to 0.1 for the ellipticity and 100° for the position angle.

Keywords

• globular cluster
• M5
• dynamical substructure