Full spectral fitting of Milky Way and M31 globular clusters: ages and metallicities

Autor(es)

Cezario, E. ^[1] ; Coelho, P. R. T. ^[1] ; Alves-Brito, A. ^[2] ; Forbes, D. A. ^[3] ; Brodie, J. P. ^[4]

Afiliação do(s) autor(es)

^[1] Univ Cruzeiro Sul, Nucleo Astrofis Teor, BR-01506000 Sao Paulo - Brazil

^[2] Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611 - Australia

^[3] Swinburne Univ Technol, Ctr Astrophys & Supercomp, Hawthorn, Vic 3122 - Australia

^[4] Univ Calif Santa Cruz, UCO Lick Observ, Santa Cruz, CA 95064 - USA

• Tipo de documento: Artigo Científico
• Fonte: Astronomy & Astrophysics; v. 549, JAN 2013.
• Citações Web of Science: 12

Resumo

Context .The formation and evolution of disk galaxies are long standing questions in astronomy. Understanding the properties of globular cluster systems can lead to important insights on the evolution of its host galaxy. Aims. We aim to obtain the stellar population parameters - age and metallicity - of a sample of M31 and Galactic globular clusters. Studying their globular cluster systems is an important step towards understanding their formation and evolution in a complete way. Methods. Our analysis employs a modern pixel-to-pixel spectral fitting technique to fit observed integrated spectra to updated stellar population models. By comparing observations to models we obtain the ages and metallicities of their stellar populations. We apply this technique to a sample of 38 globular clusters in M31 and to 41 Galactic globular clusters, used as a control sample. Results. Our sample of M31 globular clusters spans ages from 150 Myr to the age of the Universe. Metallicities {[}Fe/H] range from -2.2 dex to the solar value. The age-metallicity relation obtained can be described as having two components: an old population with a flat age-{[}Fe/H] relation, possibly associated with the halo and/or bulge, and a second one with a roughly linear relation between age and metallicity, higher metallicities corresponding to younger ages, possibly associated with the M31 disk. While we recover the very well known Galactic GC metallicity bimodality, our own analysis of M31's metallicity distribution function (MDF) suggests that both GC systems cover basically the same {[}Fe/H] range yet M31's MDF is not clearly bimodal. These results suggest that both galaxies experienced different star formation and accretion histories. (AU)

• Processo FAPESP: 08/58406-4 - A modelagem de populações estelares e padrões de abundância detalhados
• Beneficiário: Paula Rodrigues Teixeira Coelho
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores