Journal
ASTROPHYSICAL JOURNAL
Volume 768, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/768/2/172
Keywords
dark matter; galaxies: dwarf; galaxies: fundamental parameters; galaxies: kinematics and dynamics; Local Group
Categories
Funding
- W. M. Keck Foundation
- Alfred P. Sloan Foundation
- National Science Foundation
- U.S. Department of Energy Office of Science
- Agence Nationale de la Recherche though the grant POMMME [ANR 09-BLAN-0228]
- ARC [DP110100678]
- Deutsche Forschungsgemeinschaft from Emmy-Noether grant [Ko 4161/1]
- University of Arizona
- Brookhaven National Laboratory
- University of Cambridge
- Carnegie Mellon University
- University of Florida
- Harvard University
- Instituto de Astrofisica de Canarias
- Johns Hopkins University
- Lawrence Berkeley National Laboratory
- Max Planck Institute for Astrophysics
- Max Planck Institute for Extraterrestrial Physics
- New Mexico State University
- New York University
- Ohio State University
- Pennsylvania State University
- University of Portsmouth
- Princeton University
- University of Tokyo
- University of Utah
- Vanderbilt University
- University of Virginia
- University of Washington
- Yale University
- [FT100100268]
- STFC [PP/E002064/1, ST/J001422/1, ST/K001000/1, ST/J000647/1] Funding Source: UKRI
- Science and Technology Facilities Council [ST/J001422/1, ST/H00243X/1, ST/J000647/1, ST/K001000/1, PP/E002064/1] Funding Source: researchfish
- Australian Research Council [FT100100268] Funding Source: Australian Research Council
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We present a homogeneous kinematic analysis of red giant branch stars within 18 of the 28 Andromeda dwarf spheroidal (dSph) galaxies, obtained using the Keck I/LRIS and Keck II/DEIMOS spectrographs. Based on their g - i colors (taken with the CFHT/MegaCam imager), physical positions on the sky, and radial velocities, we assign probabilities of dSph membership to each observed star. Using this information, the velocity dispersions, central masses, and central densities of the dark matter halos are calculated for these objects, and compared with the properties of the Milky Way dSph population. We also measure the average metallicity ([Fe/H]) from the co-added spectra of member stars for each M31 dSph and find that they are consistent with the trend of decreasing [Fe/H] with luminosity observed in the Milky Way population. We find that three of our studied M31 dSphs appear as significant outliers in terms of their central velocity dispersion, And XIX, XXI, and XXV, all of which have large half-light radii (greater than or similar to 700 pc) and low velocity dispersions (sigma(v) < 5km s(-1)). In addition, And XXV has a mass-to-light ratio within its half-light radius of just [M/L](half) = 10.3(-6.7)(+7.0), making it consistent with a simple stellar system with no appreciable dark matter component within its 1 sigma uncertainties. We suggest that the structure of the dark matter halos of these outliers have been significantly altered by tides.
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