AGB stars in the SMC: evolution and dust properties based on Spitzer observations

Dell'Agli, F.; García-Hernández, D. A.; Ventura, P.; Schneider, R.; Di Criscienzo, M.; Rossi, C.
Referencia bibliográfica

Monthly Notices of the Royal Astronomical Society, Volume 454, Issue 4, p.4235-4249

Fecha de publicación:
12
2015
Número de autores
6
Número de autores del IAC
1
Número de citas
50
Número de citas referidas
45
Descripción
We study the population of asymptotic giant branch (AGB) stars in the Small Magellanic Cloud (SMC) by means of full evolutionary models of stars of mass 1 M⊙ ≤ M ≤ 8 M⊙, evolved through the thermally pulsing phase. The models also account for dust production in the circumstellar envelope. We compare Spitzer infrared colours with results from theoretical modelling. We show that ˜75 per cent of the AGB population of the SMC is composed by scarcely obscured objects, mainly stars of mass M ≤ 2 M⊙ at various metallicity, formed between 700 Myr and 5 Gyr ago; ˜70 per cent of these sources are oxygen-rich stars, while ˜30 per cent are C-stars. The sample of the most obscured AGB stars, accounting for ˜25 per cent of the total sample, is composed almost entirely by carbon stars. The distribution in the colour-colour ([3.6] - [4.5], [5.8] - [8.0]) and colour-magnitude ([3.6] - [8.0], [8.0]) diagrams of these C-rich objects, with a large infrared emission, traces an obscuration sequence, according to the amount of carbonaceous dust in their surroundings. The overall population of C-rich AGB stars descends from 1.5-2 M⊙ stars of metallicity Z = 4 × 10-3, formed between 700 Myr and 2 Gyr ago, and from lower metallicity objects, of mass below 1.5 M⊙, 2-5 Gyr old. We also identify obscured oxygen-rich stars (M ˜ 4-6 M⊙) experiencing hot bottom burning. The differences between the AGB populations of the SMC and LMC are also commented.
Proyectos relacionados
Project Image
Nucleosíntesis y procesos moleculares en los últimos estados de la evolución estelar
Las estrellas de masa baja e intermedia (M < 8 masas solares, Ms) representan la mayoría de estrellas en el Cosmos y terminan sus vidas en la Rama Asintótica de las Gigantes (AGB) - justo antes de formar Nebulosas Planetarias (NPs) - cuando experimentan procesos nucleosintéticos y moleculares complejos. Las estrellas AGB son importantes
Domingo Aníbal
García Hernández