STROMGREN PHOTOMETRY OF GALACTIC GLOBULAR CLUSTERS. II. METALLICITY DISTRIBUTION OF RED GIANTS IN ω CENTAURI

被引：48

作者：

Calamida, A. ^{[1
,2
,3
]}

Bono, G. ^{[2
,3
]}

Stetson, P. B. ^{[4
]}

Freyhammer, L. M. ^{[5
]}

Piersimoni, A. M. ^{[6
]}

Buonanno, R. ^{[2
,3
]}

Caputo, F. ^{[3
]}

Cassisi, S. ^{[6
]}

Castellani, M. ^{[3
]}

Corsi, C. E. ^{[3
]}

Dall'Ora, M. ^{[7
]}

Degl'Innocenti, S. ^{[8
,9
]}

Ferraro, I. ^{[3
]}

Grundahl, F. ^{[10
]}

Hilker, M. ^{[1
]}

Iannicola, G. ^{[3
]}

Monelli, M. ^{[11
]}

Nonino, M. ^{[12
]}

Patat, N. ^{[3
]}

Pietrinferni, A. ^{[6
]}

Moroni, P. G. Prada ^{[8
,9
]}

Primas, F. ^{[1
]}

Pulone, L. ^{[3
]}

Richtler, T. ^{[13
]}

Romaniello, M. ^{[1
]}

Storm, J. ^{[14
]}

Walker, A. R. ^{[15
]}

机构：

[1] European So Observ, D-85748 Garching, Germany

[2] Univ Roma Tor Vergata, I-00133 Rome, Italy

[3] INAF Osservatorio Astron Roma, I-00040 Monte Porzio Catone, Italy

[4] Natl Res Council Canada, Herzberg Inst Astrophys, Dominion Astrophys Observ, Victoria, BC V9E 2E7, Canada

[5] Univ Cent Lancashire, Ctr Astrophys, Preston PR1 2HE, Lancs, England

[6] INAF Osservatorio Astron Collurania, I-64100 Teramo, Italy

[7] INAF Osservatorio Astron Capodimonte, I-80131 Naples, Italy

[8] Univ Pisa, Dipartimento Fis E Fermi, I-56127 Pisa, Italy

[9] INFN, Sez Pisa, I-56127 Pisa, Italy

[10] Aarhus Univ, Dept Phys & Astron, DK-8000 Aarhus C, Denmark

[11] Inst Astrofis Canarias, E-38200 San Cristobal la Laguna, Tenerife, Spain

[12] INAF Osservatorio Astron Trieste, Trieste, Italy

[13] Univ Concepcion, Dept Fis, Concepcion, Chile

[14] Astrophys Inst Potsdam, D-14482 Potsdam, Germany

[15] Cerro Tololo Interamer Observ, La Serena, Chile

来源：

ASTROPHYSICAL JOURNAL | 2009年 / 706卷 / 02期

基金：

美国国家科学基金会; 美国国家航空航天局;

关键词：

globular clusters: general; globular clusters: individual (Omega Centauri); stars: abundances; stars: evolution; MAIN-SEQUENCE; STELLAR POPULATIONS; CCD PHOTOMETRY; RESOLUTION SPECTROSCOPY; CHEMICAL INHOMOGENEITY; HOMOGENEOUS PHOTOMETRY; COLOR TRANSFORMATIONS; ABUNDANCE PATTERNS; UVBY PHOTOMETRY; BRIGHT STARS;

D O I：

10.1088/0004-637X/706/2/1277

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

We present new intermediate-band Stromgren photometry based on more than 300 u, v, b, y images of the Galactic globular cluster omega Cen. Optical data were supplemented with new multiband near-infrared (NIR) photometry (350 J, H, K-s images). The final optical-NIR catalog covers a region of more than 20 x 20 arcmin squared across the cluster center. We use different optical-NIR color-color planes together with proper-motion data available in the literature to identify candidate cluster red-giant (RG) stars. By adopting different Stromgren metallicity indices, we estimate the photometric metallicity for approximate to 4000 RGs, the largest sample ever collected. The metallicity distributions show multiple peaks ([Fe/H](phot) =-1.73 +/- 0.08, -1.29 +/- 0.03, -1.05 +/- 0.02, -0.80 +/- 0.04, -0.42 +/- 0.12, and -0.07 +/- 0.08 dex) and a sharp cutoff in the metal-poor (MP) tail ([Fe/H](phot) less than or similar to -2 dex) that agree quite well with spectroscopic measurements. We identify four distinct subpopulations, namely, MP ([Fe/H] <= -1.49), metal-intermediate (MI;-1.49 < [Fe/H] <= -0.93), metal-rich (MR; -0.95 < [Fe/H] <= -0.15), and solar metallicity ([Fe/H] approximate to 0). The last group includes only a small fraction of stars (similar to 8% +/- 5%) and should be confirmed spectroscopically. Moreover, using the difference in metallicity based on different photometric indices, we find that the 19% +/- 1% of RGs are candidate CN-strong stars. This fraction agrees quite well with recent spectroscopic estimates and could imply a large fraction of binary stars. The Stromgren metallicity indices display a robust correlation with alpha-elements ([Ca+Si/H]) when moving from the MI to the MR regime ([Fe/H] greater than or similar to -1.7 dex).

引用

页码：1277 / 1298

页数：22

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