Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...20917803w&link_type=abstract
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #178.03; Bulletin of the American Astronomical Society,
Astronomy and Astrophysics
Astronomy
Scientific paper
I present results from a large spectroscopic survey of individual stars in dwarf spheroidal (dSph) galaxies, conducted using the Michigan/MIKE Fiber System (MMFS) at the Magellan Telescopes. dSph galaxies have come under intense scrutiny because they represent the lower extreme of the galaxy mass function, and thereby provide important constraints on models of structure formation. The proximity of the Milky Way's (MW's) dSph satellites allows us to study the resolved stellar populations of these systems in detail. Toward this end I have acquired MMFS spectra (5140-5180 Angstroms at resolution 20000) for more than 5000 stars in the MW dSphs Carina, Fornax, Sculptor, and Sextans. The spectra yield measurements of both radial velocity (median precision ± 1.8 km/s) and [Fe/H] metallicity (± 0.2 dex). I present radial velocity dispersion profiles for each dSph, as well as halo mass profiles derived using a variety of models and nonparametric estimation techniques. In some cases, the bulk stellar component is separable into populations following distinct distributions in position, kinematics, and chemistry, indicating a surprising level of complexity in these diminutive galaxies. Taking advantage of the fine spatial sampling of the MMFS data, I identify regions showing tentative evidence of localized chemo-dynamical substructure.
This work is supported by grants from the National Science Foundation and the University of Michigan.
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