METAL ABUNDANCES OF RR LYRAE VARIABLES IN SELECTED GALACTIC STAR FIELDS .5. THE LICK ASTROGRAPHIC FIELDS AT INTERMEDIATE GALACTIC LATITUDES

被引:181
作者
SUNTZEFF, NB
KINMAN, TD
KRAFT, RP
机构
[1] KITT PEAK NATL OBSERV,NATL OPT ASTRON OBSERV,TUCSON,AZ 85726
[2] UNIV CALIF SANTA CRUZ,LICK OBSERV,BOARD STUDIES ASTRON & ASTROPHYS,MT HAMILTON,CA 95140
关键词
CLUSTERS; GLOBULAR; GALAXIES; STELLAR CONTENT; THE GALAXY; STARS; ABUNDANCES; POPULATION-II; RR LYRAE;
D O I
10.1086/169650
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We derive DELTA-S metallicities for 60 RR Lyrae variables in three new Lick Astrographic Survey fields at intermediate Galactic latitudes: (l, b) = (86-degrees, + 35-degrees), (52-degrees, + 35-degrees), and (18-degrees, + 25-degrees). DETLA-S values are also given for five nearby field RR Lyraes without previously published values, and improved DELTA-S values are listed for 24 nearby RR Lyraes. We have combined these data with the data from the previous Lick surveys and the work of Saha and Oke to study the nature of the Galactic holo in the galactocentric distance range 4-30 kpc based on 171 RR Lyraes. We find that the nature of the metallicity of the Galactic halo changes at the solar circle. Outside the solar circle, the metallicity gradient is zero as a function of R or [z[. The average DELTA-S outside the solar circle corresponds <]Fe/H[> = -1.65 with dispersion of 0.30 dex. Inside the solar circle, the gradient in [Fe/H] is -0.06 dex kpc-1. In comparison with the globular cluster population, outside the solar circle the field RR lyraes and globular clusters have the same mean metallicity and dispersion, while inside the solar circle the field RR Lyraes are more metal-rich than the globular clusters. However, when the field RR Lyraes are compared with the RR Lyraes in globular clusters, we find that the metallicity distribution is the same over the whole distance range. On the assumption that the two populations are the same, we derive a ratio of globular cluster mass to halo mass of 0.02, a luminous halo mass of approximately 9 x 10(8) M. in the range 4-25 kpc, and a local space density for luminous halo matter of 5.5 +/- 1.8 x 10(-5) M. pc-3. The ratio of solar neighborhood metal-rich to metal-poor RR Lyraes is shown to be consistent with the probability of formation of an RR Lyrae in the thick disk versus the halo population. Finally, we show that the field RR Lyraes obey a period-shift-metallicity relationship similar to that in the globular clusters, and that the field RR Lyraes also exhibit the two "Oosterhoff" groups seen in the clusters.
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页码:528 / 546
页数:19
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