| Texto completo | |
| Autor(es): |
Lepine, J. R. D.
[1]
;
Cruz, P.
[2]
;
Scarano, Jr., S.
[1]
;
Barros, D. A.
[1]
;
Dias, W. S.
[3]
;
Pompeia, L.
[4]
;
Andrievsky, S. M.
[5, 6, 7, 8]
;
Carraro, G.
[9]
;
Famaey, B.
[10, 11]
Número total de Autores: 9
|
| Afiliação do(s) autor(es): Mostrar menos - | [1] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508090 Sao Paulo - Brazil
[2] CAB INTA CSIC, Ctr Astrobiol, Dept Astrofis, Madrid 28850 - Spain
[3] Univ Fed Itajuba, DFQ Inst Ciencias Exatas, UNIFEI, BR-37500903 Itajuba, MG - Brazil
[4] Univ Libre Bruxelles, Inst Astron & Astrophys, B-1050 Brussels - Belgium
[5] Odessa Natl Univ, Dept Astron, UA-65014 Odessa - Ukraine
[6] Odessa Natl Univ, Astron Observ, UA-65014 Odessa - Ukraine
[7] Isaac Newton Inst Chile, Odessa Branch, UA-65014 Odessa - Ukraine
[8] Univ Paris Diderot, CNRS, Observ Paris Meudon, GEPI, F-92125 Meudon - France
[9] ESO, Alonso De Cordova 3107, Santiago De Chi - Chile
[10] Univ Strasbourg, CNRS, UMR 7550, Astron Observ, F-67000 Strasbourg - France
[11] Univ Bonn, AIfA, D-53121 Bonn - Germany
Número total de Afiliações: 11
|
| Tipo de documento: | Artigo Científico |
| Fonte: | Monthly Notices of the Royal Astronomical Society; v. 417, n. 1, p. 698-708, OCT 2011. |
| Citações Web of Science: | 81 |
| Resumo | |
The connection between some features of the metallicity gradient in the Galactic disc, best revealed by Open Clusters and Cepheids, and the spiral structure, has been explored. The step-like abrupt decrease in metallicity at 8.5 kpc (with R(0) = 7.5 kpc, or at 9.5 kpc if R(0) = 8.5 kpc is adopted) is well explained by the corotation ring-shaped gap in the density of gas, which isolates the internal and external regions of the disc one from the other. This solves the long-standing problem of a lack of understanding of the different chemical characteristics of the inner and outer parts of the disc. The time required to build up the metallicity difference between the two sides of the step is a measure of the minimal lifetime of the present grand-design spiral pattern structure, of the order of 3 Gyr. The plateaux observed on both sides of the step are interpreted in terms of the large-scale radial motion of the stars and of the gas flow induced by the spiral structure. The star formation rate revealed by the density of open clusters is maximum in the Galactic radial range from 6 to 12 kpc (with an exception of a narrow gap at corotation), coinciding with the region where the four-arms mode is allowed to exist. We argue that most of the old open clusters situated at large Galactocentric radii were born in this inner region where conditions more favourable for star formation are found. The ratio of a-elements to Fe of the sample of Cepheids does not vary appreciably with the Galactic radius, which reveals a homogeneous history of star formation. Different arguments are forwarded to show that the usual approximations of chemical evolution models, which assume fast mixing of metallicity in the azimuthal direction and ignore the existence of the spiral arms, are poor ones. (AU) | |
| Processo FAPESP: | 08/06304-3 - Aglomerados Abertos e Metalicidade no Disco Galáctico |
| Beneficiário: | Patricia Cardoso Cruz |
| Modalidade de apoio: | Bolsas no Brasil - Doutorado |