Ca II Triplet Spectroscopy of Small Magellanic Cloud Red Giants. VI. Analysis of chemical properties of the Main Body

B.J. DE BORTOLI; M.C. PARISI; L.P. BASSINO; D. GEISLER; B. DIAS; G. GIMENO; M.S. ANGELO; F. MAURO

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2022 vol. 664 p. 168 - 179

0004-6361

Aims. We aim to analyze the chemical evolution of the Main Body of the SMC, adding six additional clusters to existing sample,based on homogeneously and accurate metallicities.Methods. We derived radial velocitities and Ca II Triplet (CaT) metallicity of more than 150 red giants stars in six SMC star clustersand their surrounding fields, with the instrument GMOS on GEMINI-S. The mean cluster radial velocity and metallicity were obtainedwith mean errors of 2.2 km s−1and 0.03 dex, while the mean field metallicities have an mean error of 0.13 dex. We add this informationto that available for another 51 clusters and 30 fields with CaT metallicities on the same scale. Using this expanded sample we analizethe chemical properties of the SMC Main Body, defined as the inner 3.4 degrees in semimajor axis.Results. We found a high probability that the metallicity distribution of the Main Body clusters is bimodal with a metal-rich and ametal-poor cluster group, having mean metallicities and dispersion of µ = −0.80, σ = 0.06 and µ = −1.15, σ = 0.10 dex, respectively.On the other hand, Main Body field stars show a unimodal metallicity distribution peaking at [Fe/H] ∼ −1 and dispersion of 0.3.Neither metal-rich nor metal-poor clusters present a metallicity gradient. However the full Main Body cluster sample and field starshave a negative metallicity gradient consistent with each other, but the one corresponding to clusters has a large error due to the largemetallicity dispersion present in the clusters studied in that region. Metal-rich clusters present a clear age-metallicity relation, whilemetal-poor clusters present no chemical enrichment throughout the life of the galaxy.Conclusions. We present observational evidence that the chemical enrichment is complex in the SMC Main Body. Two clustergroups with potential different origins could be coexisting in the Main Body. More data with precise and homogeneous metallicitiesand distances are needed and dynamical simulations are required to understand possible different origins for the two possible clustergroups.