TY - JOUR
T1 - Structural and kinematic parameters of the two halo components of the milky way
T2 - Preliminary results
AU - Carollo, Daniela
AU - Beers, Timothy C.
AU - Chiba, Masashi
AU - Norris, John E.
AU - Lee, Young Sun
AU - Freeman, Kenneth C.
PY - 2008
Y1 - 2008
N2 - The structure of the halo of the Milky Way has recently been shown to be clearly divisible into two overlapping stellar components, the inner and the outer halo. The first structure dominates at Galactocentric distances R < 10-15 kpc, exhibits highly eccentric orbits, has a slightly pro-grade rotation, and comprises stars with a peak in their metallicity distribution function (MDF) around [Fe/H] = -1.6. The outer-halo component dominates at R > 15-20 kpc, exhibits a much more uniform distribution of orbital eccentricities, has a clear (and statistically significant) net retrograde rotation, and comprises stars with a peak in their MDF a factor of three lower than the inner halo ([Fe/H] = -2.2). Such properties indicate that one might associate two distinct modes of formation, and timescales, for the assembly of these two structures. The dataset upon which these claims are based has recently been increased by 50% with the addition of new stars from SDSS/SEGUE. We present the first results of a Maximum Likelihood technique that provides estimates for the structural parameters of the inner- and outer-halo components, including estimates of the fraction of stars within each population as a function of distance. Such numbers are critical for refining ongoing and future searches for the most metal-poor stars in the Galaxy.
AB - The structure of the halo of the Milky Way has recently been shown to be clearly divisible into two overlapping stellar components, the inner and the outer halo. The first structure dominates at Galactocentric distances R < 10-15 kpc, exhibits highly eccentric orbits, has a slightly pro-grade rotation, and comprises stars with a peak in their metallicity distribution function (MDF) around [Fe/H] = -1.6. The outer-halo component dominates at R > 15-20 kpc, exhibits a much more uniform distribution of orbital eccentricities, has a clear (and statistically significant) net retrograde rotation, and comprises stars with a peak in their MDF a factor of three lower than the inner halo ([Fe/H] = -2.2). Such properties indicate that one might associate two distinct modes of formation, and timescales, for the assembly of these two structures. The dataset upon which these claims are based has recently been increased by 50% with the addition of new stars from SDSS/SEGUE. We present the first results of a Maximum Likelihood technique that provides estimates for the structural parameters of the inner- and outer-halo components, including estimates of the fraction of stars within each population as a function of distance. Such numbers are critical for refining ongoing and future searches for the most metal-poor stars in the Galaxy.
UR - http://www.scopus.com/inward/record.url?scp=84887304263&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:84887304263
SN - 1824-8039
JO - Proceedings of Science
JF - Proceedings of Science
ER -