Far-ultraviolet investigation into the galactic globular cluster M30
  (NGC 7099): I. Photometry and radial distributions
  We present a far-ultraviolet (FUV) study of the globular cluster M30 (NGC
7099). The images were obtained using the Advanced Camera for Surveys (ACS/SBC,
F150LP, FUV) and the Wide Field Planetary Camera 2 (WFPC2, F300W, UV) which
were both on board the Hubble Space Telescope (HST). The FUV-UV
colour-magnitude diagram (CMD) shows a main sequence (MS) turnoff at FUV
$\approx$ 22 mag and FUV-UV $\approx$ 3 mag. The MS extends 4 mag below the
turnoff, and a prominent horizontal branch (HB) and blue straggler (BS)
sequence can be seen. A total of 1218 MS stars, 185 red giant branch stars, 47
BS stars and 41 HB stars are identified, along with 78 sources blueward of the
MS which consist of white dwarfs (WDs) and objects in the gap between the WDs
and the MS that include potential cataclysmic variable (CV) candidates. The
radial distribution of the BS population is concentrated towards the cluster
centre, indicating that mass segregation has occurred. The blue and red
sub-populations of the double BS sequence appear mixed in the ultraviolet CMD,
and no significant central concentration of CV candidates is seen in this
cluster.
