Carbon-Enhanced Metal-Poor Stars in the Inner and Outer Halo Components of the Milky Way

Details Carbon-Enhanced Metal-Poor Stars in the Inner and Outer Halo Components of the Milky Way Carbon-Enhanced Metal-Poor Stars in the Inner and Outer Halo Components of the Milky Way

2011-03-15

arxiv.org/abs/1103.3067v2

Astronomy and Astrophysics

Astrophysics

Galaxy Astrophysics

Accepted for publication in the Astrophysical Journal, 32 pages, 15 figures

Scientific paper

(Abridged) Carbon-enhanced metal-poor (CEMP) stars in the halo components of the Milky Way are explored, based on accurate determinations of the carbon-to-iron ([C/Fe]) abundance ratios and kinematic quantities for over 30000 calibration stars from the Sloan Digital Sky Survey (SDSS). Using our present criterion that low-metallicity stars exhibiting [C/Fe] ratios ("carbonicity") in excess of [C/Fe]$ = +0.7$ are considered CEMP stars, the global frequency of CEMP stars in the halo system for \feh\ $< -1.5$ is 8%; for \feh\ $< -2.0$ it is 12%; for \feh\ $<-2.5$ it is 20%. We also confirm a significant increase in the level of carbon enrichment with declining metallicity, growing from $<$[C/Fe]$>$ $\sim +1.0$ at \feh\ $= -1.5$ to $<$[C/Fe]$>$ $\sim +1.7$ at \feh\ $= -2.7$. The nature of the carbonicity distribution function (CarDF) changes dramatically with increasing distance above the Galactic plane, $|$Z$|$. For $|$Z$|$ $< 5$ kpc, relatively few CEMP stars are identified. For distances $|$Z$|$ $> 5$ kpc, the CarDF exhibits a strong tail towards high values, up to [C/Fe] $>$ +3.0. We also find a clear increase in the CEMP frequency with $|$Z$|$. For stars with $-2.0 <$ [Fe/H] $< -$1.5, the frequency grows from 5% at $|$Z$|$ $\sim 2$ kpc to 10% at $|$Z$|$ $\sim 10$ kpc. For stars with [Fe/H] $< -$2.0, the frequency grows from 8% at $|$Z$|$ $\sim 2$ kpc to 25% at $|$Z$|$ $\sim 10$ kpc. For stars with $-2.0 <$ [Fe/H] $< -$1.5, the mean carbonicity is $<$[C/Fe]$>$ $\sim +1.0$ for 0 kpc $<$ $|$Z$|$ $<$ 10 kpc, with little dependence on $|$Z$|$; for [Fe/H] $< -$2.0, $<$[C/Fe]$>$ $\sim +1.5$, again roughly independent of $|$Z$|$.

Affiliated with

Also associated with

No associations

Rating

Carbon-Enhanced Metal-Poor Stars in the Inner and Outer Halo Components of 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 Carbon-Enhanced Metal-Poor Stars in the Inner and Outer Halo Components of the Milky Way, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Carbon-Enhanced Metal-Poor Stars in the Inner and Outer Halo Components of the Milky Way will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-261727