2000/04/27 by Puragra Guhathakurta, David B. Reitzel, E. K. Grebel +1 · 2 citations
Physics and Astronomy · #Andromeda Galaxy #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Galactic halo #Galaxies: Formation, Evolution, Phenomena #Galaxy #Globular cluster #Halo #Local Group #Metallicity #Milky Way #Physics #Radial velocity #Red-giant branch #Stars #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1117/12.390140
12 pages, 7 figures, Proceedings of SPIE Conference: Discoveries and Research Prospects with 8-10 Meter Class Telescopes (Munich March 2000)
arxiv created 2000/04/27 · openalex publication_date 2000/06/29 · arxiv updated 2015/06/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present Keck 10-meter/LRIS spectra of candidate red giants in the halo of M31, located at a projected radius of R equals 19kpc on the minor axis. These spectroscopic targets have been selected using a combination of UBRI-based and morphological screening to eliminate background galaxies. Radial velocity measurements are used to separate M312 halo giants from foreground Milky Way dwarf stars, M31 disk stars, and residual background galaxies. The metallicity of each M31 halo giant is measured using standard photometric and spectroscopic techniques, the latter based on the strength of the Ca II triplet. The various (Fe/H) estimates are in rough agreement with one another. The data reveal a large spread in (Fe/H) in M31's halo; there is no strong radial (Fe/H) gradient. LRIS and HIRES spectra are also presented for red giants in five dwarf spheroidal satellites of M31: AndI, AndIII, AndV, AndVI, and AndVII. There appears to be a significant metallicity spread in AndVI and possibly in AndI. The new radial velocity data on these outer dwarfs are used to constrain the total mass of M31: the best estimate in under 10<SUP>12</SUP> M, somewhat less than the best estimate for the Milky Way.