The Postcollapse Core of M15 Imaged with the HST Planetary Camera
Schneider, Donald P.; Lauer, Tod R.; Faber, S. M.; Currie, Douglas G.; Holtzman, Jon A.; Groth, Edward J.; Light, Robert M.; O'Neil, Earl J., Jr.; Baum, William A.; Ewald, S. P.; Hester, J. Jeff; Shaya, Edward J.; Westphal, James A.; Kelsall, T.; Lynds, C. Roger
United States
Abstract
It is shown here that, despite the severe spherical aberration present in the HST, the Wide Field/Planetary Camera (WFPC) images still present useful high-resolution information on M15, the classic candidate for a cluster with a collapsed core. The stars in M15 have been resolved down to the main-sequence turnoff and have been subtracted from the images. The remaining faint, unresolved stars form a diffuse background with a surprisingly large core with r(c) = 0.13 pc. The existence of a large core interior to the power-law cusp may imply that M15 has evolved well past maximum core collapse and may rule out the presence of a massive central black hole as well.