TY - JOUR
T1 - Abundances for a large sample of red giants in NGC 1851
T2 - Hints for a merger of two clusters?
AU - Carretta, Elisa
AU - Gratton, Raffaele G.
AU - Lucatello, Sara
AU - Bragaglia, Angela
AU - Catanzaro, Giovanni
AU - Leone, Francesco
AU - Momany, Yazan
AU - D'Orazi, V.
AU - Cassisi, Santi
AU - D'Antona, Francesca
AU - Ortolani, S.
PY - 2010/10/10
Y1 - 2010/10/10
N2 - We present the abundance analysis of a sample of more than 120 red giants in the globular cluster (GC) NGC 1851, based on FLAMES spectra. We find a small but detectable metallicity spread. This spread is compatible with the presence of two different groups of stars with a metallicity difference of 0.06-0.08 dex, in agreement with earlier photometric studies. If stars are divided into these two groups according to their metallicity, both components show Na-O anticorrelation (signature of a genuine GC nature) of moderate extension. The metal-poor stars are more concentrated than the metal-rich ones.We tentatively propose the hypothesis that NGC 1851 formed from a merger of two individual GCs with a slightly different Fe and α-element content and possibly an age difference up to 1 Gyr. This is also supported by number ratios of stars on the split subgiant and on the bimodal horizontal branches. The distribution of n-capture process elements in the two components also supports the idea that the enrichment must have occurred in each of the structures separately and not as a continuum of events in a single GC. The most probable explanation is that the proto-clusters formed into a (now dissolved) dwarf galaxy and later merged to produce the present GC.
AB - We present the abundance analysis of a sample of more than 120 red giants in the globular cluster (GC) NGC 1851, based on FLAMES spectra. We find a small but detectable metallicity spread. This spread is compatible with the presence of two different groups of stars with a metallicity difference of 0.06-0.08 dex, in agreement with earlier photometric studies. If stars are divided into these two groups according to their metallicity, both components show Na-O anticorrelation (signature of a genuine GC nature) of moderate extension. The metal-poor stars are more concentrated than the metal-rich ones.We tentatively propose the hypothesis that NGC 1851 formed from a merger of two individual GCs with a slightly different Fe and α-element content and possibly an age difference up to 1 Gyr. This is also supported by number ratios of stars on the split subgiant and on the bimodal horizontal branches. The distribution of n-capture process elements in the two components also supports the idea that the enrichment must have occurred in each of the structures separately and not as a continuum of events in a single GC. The most probable explanation is that the proto-clusters formed into a (now dissolved) dwarf galaxy and later merged to produce the present GC.
KW - Globular clusters: general
KW - Globular clusters: individual (NGC 1851)
KW - Stars: abundances
KW - Stars: evolution
KW - Stars: Population II
UR - http://www.scopus.com/inward/record.url?scp=78649285191&partnerID=8YFLogxK
U2 - 10.1088/2041-8205/722/1/L1
DO - 10.1088/2041-8205/722/1/L1
M3 - Article
AN - SCOPUS:78649285191
VL - 722
JO - The Astrophysical Journal Letters
JF - The Astrophysical Journal Letters
SN - 2041-8205
IS - 1 PART 2
ER -