Chemical Abundances of the Outer Halo Stars in the Milky Way

Details Chemical Abundances of the Outer Halo Stars in the Milky Way Chemical Abundances of the Outer Halo Stars in the Milky Way

2009-12-02

arxiv.org/abs/0912.0329v1

Astronomy and Astrophysics

Astrophysics

Galaxy Astrophysics

68 pages with 23 figures, Accepted for publication in PASJ

Scientific paper

We present chemical abundances of 57 metal-poor stars that are likely constituents of the outer stellar halo in the Milky Way. Almost all of the sample stars have an orbit reaching a maximum vertical distance (Z_max) of >5 kpc above and below the Galactic plane. High-resolution, high signal-to-noise spectra for the sample stars obtained with Subaru/HDS are used to derive chemical abundances of Na, Mg, Ca, Ti, Cr, Mn, Fe, Ni, Zn, Y and Ba with an LTE abundance analysis code. The resulting abundance data are combined with those presented in literature that mostly targeted at smaller Z_max stars, and both data are used to investigate any systematic trends in detailed abundance patterns depending on their kinematics. It is shown that, in the metallicity range of -2<[Fe/H]<-1, the [Mg/Fe] ratios for the stars with Z_max>5 kpc are systematically lower (~0.1 dex) than those with smaller Z_max. This result of the lower [alpha/Fe] for the assumed outer halo stars is consistent with previous studies that found a signature of lower [alpha/Fe] ratios for stars with extreme kinematics. A distribution of the [Mg/Fe] ratios for the outer halo stars partly overlaps with that for stars belonging to the Milky Way dwarf satellites in the metallicity interval of -2<[Fe/H]<-1 and spans a range intermediate between the distributions for the inner halo stars and the stars belonging to the satellites. Our results confirm inhomogeneous nature of chemical abundances within the Milky Way stellar halo depending on kinematic properties of constituent stars as suggested by earlier studies. Possible implications for the formation of the Milky Way halo and its relevance to the suggested dual nature of the halo are discussed.

Affiliated with

Also associated with

No associations

Rating

Chemical Abundances of the Outer Halo Stars in the Milky Way does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Chemical Abundances of the Outer Halo Stars in the Milky Way, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Chemical Abundances of the Outer Halo Stars in the Milky Way will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-508271