2002/11/29 by Bacham E. Reddy, Jocelyn Tomkin, David L. Lambert +1 · 2 citations
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.2003.06305.x
published as Mon.Not.Roy.Astron.Soc. 340 (2003) 304 · 51 pages (includes 19 figures and 6 tables). To appear in MNRAS (paper has been replaced: typos added, In Table~1, [Fe/H]phot has been replaced by spectroscopic [Fe/H] that are used in the plots) (Table1, photometric[Fe/H] values are replaced by spectroscopically derived [Fe/H] that are used in the plots)
Photospheric abundances are presented for 27 elements from carbon to europium in 181 F-G dwarfs from a differential LTE analysis of high-resolution and high signal-to-noise spectra. Stellar T\rm eff were adopted from an infrared flux method calibration of Strömgren photometry. Stellar log g were calculated from \it Hipparcos parallaxes and stellar evolutionary tracks. Stellar space motions (U, V, W) and a Galactic potential were used to estimate Galactic orbital parameters. Results of α-elements -- O, Mg, Si, Ca, and Ti -- show [α/Fe] to increase slightly with decreasing [Fe/H]. Heavy elements with dominant contributions at solar metallicity from the s-process show [s/Fe] to decrease slightly with decreasing [Fe/H]. Scatter in [X/Fe] at a fixed [Fe/H] is entirely attributable to the small measurement errors, after excluding the few thick disc stars and the s-process enriched CH subgiants. Tight limits are set on `cosmic' scatter. By combining our sample with published studies, thick disc stars are identified by their VLSR in the range - 40 to -100 km s-1. These are very old stars with origins in the inner Galaxy and metallicities [Fe/H] ≤ -0.4. At the same [Fe/H], the sampled thin disc stars have VLSR ∼ 0 km s-1, and are generally younger with a birthplace at about the Sun's Galactocentric distance. In the range -0.35 ≥ [Fe/H] ≥ -0.70, well represented by present thin and thick disc samples, [X/Fe] of the thick disc stars is greater than that of thin disc stars for Mg, Al, Si, Ca, Ti, and Eu. [X/Fe] is very similar for the thin and thick disc for -- notably -- Na, and iron-group elements.