J/AJ/108/1016 J/AJ/108/1016 Kinematics of local RR lyrae stars. I. A C Layden Astron. J. 108 1016 1994 1994AJ....108.1016L J/AJ/110/2288 : Kinematics of local RR Lyrae. II. (Layden 1995) Abundances, [Fe/H] Photometry Radial velocities Stars, variable In order to study the structure and formation history of the galaxy, we have obtained low-to-moderate dispersion spectra of 302 nearby RR Lyrae variables of Bailey type "ab". We derived abundances, typically accurate to 0.15-0.20dex and calibrated to the Zinn & West (1984ApJS...55...45Z) globular cluster metallicity scale, from the pseudo-equivalent widths of the Ca II K, Hdelta, Hgamma, and Hbeta lines. Radial velocities accurate to between 2 and 30km/s were obtained from the spectra and from the literature. Distances accurate to between 5% and 20% were derived from published apparent magnitudes and Burstein & Heiles (1982AJ.....87.1165B) reddenings. The metallicity distribution of the RR Lyrae stars peaks at [Fe/H]_K_{approx}-1.5, and is narrower than that of the Ryan & Norris (1991AJ....101.1865R) subdwarfs, as expected since the most metal-rich and metal-poor progenitors preferentially appear as stable red and blue horizontal branch stars, rather than as RR Lyrae. The metal-rich tail of the RR Lyrae distribution extends to [Fe/H]_K_{approx}0, and a qualitative analysis of the distribution of distances from the galactic plane shows that the stars in this tail (i.e., [Fe/H]_K_>-1.0) are more concentrated to the plane than the more metal-poor stars. The abundance distribution of the local RR Lyrae stars is in excellent agreement with the changing abundance distributions of distant RR Lyrae stars as a function of galactocentric distance, as derived by Suntzeff et al. (1991ApJ...367..528S), who ascribed this change to systematic variations in horizontal branch morphology (probably age variations) with galactocentric distance. The abundance distribution of the local RR Lyrae stars also agrees well with those of the distant RR Lyrae stars as a function of distance from the galactic plane. There is no evidence for an abundance gradient in this direction, suggesting that gaseous dissipation did not play a major role in the formation of the outer halo.

Name Variable star name (as in GCVS4, <II/139>) --- [Fe/H] Metal abundance, on Zinn & West (1984ApJS...55...45Z) scale Sun u_[Fe/H] Uncertainty flag on [Fe/H] --- e_[Fe/H] rms uncertainty on [Fe/H] Sun o_[Fe/H] Number of spectra used for [Fe/H] estimate --- <V> Intensity-averaged V magnitude (see n_<V>) mag r_<V> Reference for <V> (see n_<V>) number=1 Intensity-averaged V magnitude reference: a = <V> value from Schmidt 1991AJ....102.1766S b = Layden (1993, Ph.D. dissertation, Yale University) photoelectric photometry c = Layden (1993, Ph.D. dissertation, Yale University) recalibration of photographic photometry d = Photometry from Nikolev et al. 1984, The Mean Light and Colour (B-V and U-B) Curves of 210 Field RR Lyrae Types Stars, (University of Sofia, Sofia) e = GCVS4 <II/139> photometry uncertain --- n_<V> Photometric passband number=2 Photometry passband: V = photoelectric V B = photoelectric B p = photographic v = (photo)visual --- AV Interstellar absorption in V number=3 Interstellar absorption in V, from Burstein & Heiles 1982AJ....187.1165B --- Dist Distance from Sun kpc e_Dist rms uncertainty on distance kpc Z Distance from Galactic plane kpc Rgc Distance from Galactic center, assumes Ro=8kpc kpc RV Systemic radial velocity km/s e_RV Estimated error in measured radial velocity km/s o_RV Number of spectra used in Vrad estimate --- Method Radial velocity combination method number=4 Radial velocity combination method: 1 = fits with standard RV curve 2 = weighted mean 3 = single observation only --- Vsys Final systemic radial velocity number=5 Final systemic radial velocity, a combination of Vrad and values from the literature km/s e_Vsys Estimated error in Vsys km/s u_Vsys ':' indicates disagreement in velocity number=6 A colon, ':', indicates the measured and literature velocity estimates disagree by more than the quoted error; the quoted error may be too small. -------------------------------------------------------------------------------- Acknowledgements: Layden A.C. <alayden@noao.edu> Department of Astronomy, Yale University, P.O. Box 208101 New Haven, Connecticut 06520-8101 AAS CD-ROM series, Volume 3, 1995 --- Lee Brotzman ADS 1994, Patricia Bauer [CDS] 16-Feb-1995Oct31 J_AJ_108_1016.xml