Globular Cluster Photometry With the Hubble Space Telescope. V. WFPC Study of M15's Central density Cusp

We describe images of the center of the dense globular cluster M15 (NGC 7078) obtained with the Hubble Space Telescope Wide Field and Planetary Camera 2 (WFPC2). Data taken in the F336W, F439W, and F555W filters (approximately U, B, and V) are used to study the surface density distribution of the $sim3 imes10^4$~stars detected in a 5~arcmin$^2$ region within $r95$% significance level. The star count profile is consistent with that expected from core-collapse models or with the predicted distribution around a massive (few times $10^3,M_odot$) black hole. The close triplet of bright stars, AC~214, is within $0.5''$ ($1.5sigma$) of the cluster centroid position.Comment: 24 pages, TeX format, 14 postscript figures, Full tables at ftp://eku.sns.ias.edu/pub/GLOBULAR_CLUSTERS/m15-wfpc2 Figure 1 available from raja@ucolick.org. Figure 2 at http://www.ucolick.org/~raja/images/m15.ubv.gif To appear in The Astronomical Journal, January 199