CCD PHOTOMETRY OF THE DISTANT SOUTHERN GLOBULAR-CLUSTER NGC-5824

CCD observations have been used to generate a V,(B-V) colour-magnitude diagram for the distant globular cluster NGC 5824. The sample consists of 285 stars reaching V= 20.5, and a well-defined blue horizontal branch is observed for the first time. Assuming a reddening of E{B-V) = 0.13, the colour of the giant branch at the level of the horizontal branch is determined to be (5-V)o,g = 0.77 and the apparent distance modulus (V-Mv) = 18.0 ± 0.2. From these, a value of [Fe/H] = - 1.7 and a heliocentric distance of 33 (± 3) kpc have been estimated for the cluster. This yields a galaeto-centric distance of 25 kpc which, when combined with Hesser, Shawl & Meyer's recent radial-velocity determination, enables the representative point of the cluster to be plotted in Lynden-Bell's velocity-distance diagram where its location is consistent with a conventional value of the mass of our Galaxy. © 1990 Oxford University Press. All rights reserved.