Broadband UBVR C I C Photometry of Horizontal‐Branch and Metal‐poor Candidates from the HK and Hamburg/ESO Surveys. I.

We report broadband UBV and/or BVRI CCD photometry for a total of 1857 starsin the thick-disk and halo populations of the Galaxy. The majority of ourtargets were selected as candidate field horizontal-branch or other A-typestars (FHB/A, N = 576), or candidate low-metallicity stars (N = 1221), from theHK and Hamburg/ESO objective-prism surveys. Similar data for a small number ofadditional stars from other samples are also reported. These data are being used for several purposes. In the case of the FHB/Acandidates they are used to accurately separate the lower-gravity FHB starsfrom various higher-gravity A-type stars, a subsample that includes theso-called Blue Metal Poor stars, halo and thick-disk blue stragglers,main-sequence A-type dwarfs, and Am and Ap stars. These data are also beingused to derive photometric distance estimates to high-velocity hydrogen cloudsin the Galaxy and for improved measurements of the mass of the Galaxy.Photometric data for the metal-poor candidates are being used to refineestimates of stellar metallicity for objects with available medium-resolutionspectroscopy, to obtain distance estimates for kinematic analyses, and toestablish initial estimates of effective temperature for analysis ofhigh-resolution spectroscopy of the stars for which this information nowexists.Comment: 22 pages, including 3 figures, 5 tables, and two ascii files of full data, accepted for publication in the Astrophysical Journal (Supplements