Elemental Abundance Ratios in Stars of the Outer Galactic Disk. III. Cepheids

Details Elemental Abundance Ratios in Stars of the Outer Galactic Disk. III. Cepheids Elemental Abundance Ratios in Stars of the Outer Galactic Disk. III. Cepheids

2005-12-13

arxiv.org/abs/astro-ph/0512348v1

Astron.J.131:2256-2273,2006

Astronomy and Astrophysics

Astrophysics

Accepted for publication in AJ

Scientific paper

10.1086/500538

We present metallicities, [Fe/H], and elemental abundance ratios, [X/Fe], for a sample of 24 Cepheids in the outer Galactic disk. The sample have Galactocentric distances covering 12 < R_GC (kpc) < 17.2 making them the most distant Galactic Cepheids upon which detailed abundance analyses have been performed. We find sub-solar ratios of [Fe/H] and overabundances of [alpha/Fe], [La/Fe], and [Eu/Fe]. All abundance ratios exhibit a dispersion that exceeds the measurement uncertainties. As seen in our previous studies of old open clusters and field giants, enhanced ratios of [alpha/Fe] and [Eu/Fe] reveal that recent star formation has taken place in the outer disk. The outer disk Cepheids appear to exhibit a bimodal distribution for [Fe/H] and [alpha/Fe]. Most of the Cepheids continue the trends with Galactocentric distance exhibited by Andrievsky's larger Cepheid sample and we refer to these stars as the "Galactic Cepheids". A minority of the Cepheids show considerably lower [Fe/H] and higher [alpha/Fe] and we refer to these stars as the "Merger Cepheids". One signature of a merger event would be composition differences between the "Galactic" and "Merger" Cepheids. The Cepheids satisfy this requirement and we speculate that the distinct compositions suggest that the "Merger Cepheids" may have formed under the influence of significant merger or accretion events. The short lifetimes of the Cepheids reveal that the merger event may be on-going with the Monoceros ring and Canis Major galaxy being possible merger candidates. [Abridged]

Affiliated with

Also associated with

No associations

Rating

Elemental Abundance Ratios in Stars of the Outer Galactic Disk. III. Cepheids 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 Elemental Abundance Ratios in Stars of the Outer Galactic Disk. III. Cepheids, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Elemental Abundance Ratios in Stars of the Outer Galactic Disk. III. Cepheids will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-80770