THE CARINA PROJECT. VII. TOWARD THE BREAKING OF THE AGE-METALLICITY DEGENERACY OF RED GIANT BRANCH STARS USING THE CU, B, I INDEX

被引：11

作者：

Monelli, M. ^{[1
,2
]}

Milone, A. P. ^{[1
,2
,3
]}

Fabrizio, M. ^{[4
]}

Bono, G. ^{[5
]}

Stetson, P. B. ^{[6
]}

Walker, A. R. ^{[7
]}

Cassisi, S. ^{[4
]}

Gallart, C. ^{[1
,2
]}

Nonino, M. ^{[8
]}

Aparicio, A. ^{[1
,2
]}

Buonanno, R. ^{[4
,5
]}

Dall'Ora, M. ^{[9
]}

Ferraro, I. ^{[10
]}

Iannicola, G. ^{[10
]}

Pulone, L. ^{[10
]}

Thevenin, F. ^{[11
]}

机构：

[1] Inst Astrofis Canarias, E-38205 Tenerife, Spain

[2] Univ La Laguna, Dept Astrofis, E-38200 Tenerife, Spain

[3] Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611, Australia

[4] Osservatorio Astron Collurania, Ist Nazl Astrofis, I-64100 Teramo, Italy

[5] Univ Roma Tor Vergata, Dipartimento Fis, I-00133 Rome, Italy

[6] NRC Herzberg, Domin Astrophys Observ, Victoria, BC V9E 2E7, Canada

[7] Cerro Tololo Interamer Observ, Natl Opt Astron Observ, La Serena, Chile

[8] Osserv Astron Trieste, Ist Nazl Astrofis, I-40131 Trieste, Italy

[9] Osserv Astron Capodimonte, INAF, I-80131 Naples, Italy

[10] Osserv Astron Roma, Ist Nazl Astrofis, I-00044 Rome, Italy

[11] Univ Nice Sophia Antipolis, CNRS, Observ Cote Azur, Lab Lagrange, F-06304 Nice, France

来源：

ASTROPHYSICAL JOURNAL | 2014年 / 796卷 / 02期

基金：

澳大利亚研究理事会;

关键词：

galaxies: abundances; galaxies: individual (Carina dSph); Local Group; techniques: photometric; techniques: spectroscopic; DWARF SPHEROIDAL GALAXY; GALACTIC GLOBULAR-CLUSTERS; DOUBLE SUBGIANT BRANCH; STELLAR POPULATIONS; FORMATION HISTORY; IRREGULAR GALAXY; LOCAL GROUP; MULTIPLE POPULATIONS; VLT/UVES ABUNDANCES; MAIN-SEQUENCE;

D O I：

10.1088/0004-637X/796/2/90

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

We present an analysis of photometric and spectroscopic data of the Carina dSph galaxy, testing a new approach similar to that used to disentangle multiple populations in Galactic globular clusters (GCs). We show that a proper color combination is able to separate a significant fraction of the red giant branch (RGB) of the two main Carina populations (the old one, similar to 12 Gyr, and the intermediate- age one, 4-8Gyr). In particular, the c(U, B, I) =(U - B) - (B - I) pseudo-color allows us to follow the RGB of both populations along a relevant portion of the RGB. We find that the oldest stars have a more negative c(U, B, I) pseudo-color than intermediate-age ones. We correlate the pseudo-color of RGB stars with their chemical properties, finding a significant trend between the iron content and the cU, B, I. Stars belonging to the old population are systematically more metal-poor ([Fe/H] = -2.32 +/- 0.08 dex) than the intermediate-age ones ([Fe/H] = -1.82 +/- 0.03 dex). This gives solid evidence of the chemical evolution history of this galaxy, and we have a new diagnostic that can allow us to break the age-metallicity degeneracy of H-burning advanced evolutionary phases. We compared the distribution of stars in the cU, B, I plane with theoretical isochrones, finding that no satisfactory agreement can be reached with models developed in a theoretical framework based on standard heavy element distributions. Finally, we discuss possible systematic differences when compared with multiple populations in GCs.

引用

页数：10