Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...20917702g&link_type=abstract
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #177.02; Bulletin of the American Astronomical Society,
Astronomy and Astrophysics
Astronomy
Scientific paper
The presence of significant amounts of substructure in the spheroids of spiral galaxies is a common prediction of hierarchical galaxy formation in Lambda-CDM cosmology. We present the discovery of kinematically-cold substructure in a few fields within the spheroid of the Andromeda Galaxy (M31). This discovery is part of an on-going large spectroscopic survey of red giant branch stars in M31 using the DEIMOS instrument on the Keck II telescope. We use a likelihood-based method that utilizes photometric and spectroscopic diagnostics to isolate M31 red giant stars from foreground Milky Way dwarf stars. This method yields a clean sample of M31 red giant stars that is essentially unbiased in radial velocity. We discuss the kinematics and metallicity of these cold components in comparison to the smooth spheroid of M31. We explore the physical origin of these substructures in the context of Fardal et al.'s (2006) recent determination of the orbit of the giant southern stream and make statistical comparisons between the observed substructures in M31 and numerical simulations of galactic halo formation.
This research was funded by grants from NSF and NASA/STScI.
Cooper Martin
Fardal Mark
Geha Marla
Gilbert Karoline
Guhathakurta Puraga
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