Far-Ultraviolet Imaging of the Globular Cluster NGC 7099 with the Second Wide-Field and Planetary Camera
Casertano, Stefano; Ballester, Gilda E.; Crisp, David; Holtzman, Jon A.; Trauger, John T.; Gallagher, John S., III; Hester, J. Jeff; Westphal, James A.; Mould, Jeremy R.; Hoessel, John G.; Clarke, John T.; Stapelfeldt, Karl R.; Burrows, Christopher J.; Griffiths, Richard E.; Scowen, Paul A.; Watson, Alan M.
Abstract
We have imaged the globular cluster NGC 7099 in the far-UV and visible with WFPC2 on the Hubble Space Telescope. Our far-UV images show a sparsely populated and fully resolved central region. The far-UV to visible color-magnitude diagram of these stars shows a well-defined horizontal branch with no evidence for hot, more evolved descendants. We find one hot horizontal branch star; the center of the cluster harbors four luminous blue stragglers. Far-UV images do not show any singularly steep density gradient at small radii among the horizontal branch stars of this -collapse cluster.