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Mapping the Galactic Halo IV. Searching for Distant Giants with the Washington System (2000)
BibTeX
@MISC{Morrison00mappingthe,
author = {Heather L. Morrison and Edward W. Olszewski and Mario Mateo and John E. Norris and Paul Harding and Kenneth C. Freeman},
title = {Mapping the Galactic Halo IV. Searching for Distant Giants with the Washington System},
year = {2000}
}
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Abstract
and Department of Physics – 2 – We critically examine the use of the Washington photometric system (with the 51 filter) for identifying distant halo giants. While this is the most powerful photometric technique for isolating G and K giant stars, spectroscopic follow-up of giant candidates is vital. There are two situations in which interlopers outnumber genuine giants in the diagnostic M −51/M −T2 plot, and are indistinguishable photometrically from the giants. (1) In deep surveys covering tens of square degrees, very metal-poor halo dwarfs are a significant contaminant. An example is our survey of the outer halo (Morrison et al. 2000a; Dohm-Palmer et al. 2000), where these metal-poor dwarfs dominate the number of photometric giant candidates at magnitudes fainter than V = 18 and cannot be isolated photometrically. (2) In deep surveys of smaller areas with low photometric precision, most objects in the giant region of the color-color plot are dwarfs whose photometric errors have moved them there. Color errors in M −51 and M −T2 need to be smaller than 0.03 mag to avoid this problem. An example of a survey whose
Keyphrases
washington system galactic halo iv distant giant deep survey color error photometric error giant star square degree outer halo genuine giant low photometric precision metal-poor dwarf giant candidate powerful photometric technique spectroscopic follow-up t2 plot significant contaminant distant halo giant photometric giant candidate color-color plot metal-poor halo dwarf giant region washington photometric system
