The Edge of the Galactic Disc

As part of a stellar population sampling program, a series of photometric probes at various field sizes and depths have been obtained in a low extinction window in the galactic anticentre direction. Such data set strong constraints on the radial structure of the disc. At the forefront of this "drilling" program, very deep CCD frames probe the most external parts of the disc. Over the whole effective magnitude range (18 to 25), all contributions in the statistics which should be expected from old disc stars beyond 6 kpc vanish, although such stars dominate by far at distances less than 5 kpc. This is the signature of a sharp cut-off in the star density: the edge of the galactic disc between 5.5 and 6 kpc. As a consequence, the galactic radius does not exceed 14 kpc (assuming $R/-/(//sun/)$=8.5). Colours of elliptical galaxies measured in the field rule out the risk of being misled by undetected extinction.Comment: 8 pages, Besancon Observatory preprint n.

The thick disk of the galaxy: sequel of a merging event

Accurate characterization of thick disc properties from recent kinematic and photometric surveys provides converging evidences that this intermediate population is a sequel of the violent heating of early disc populations by a merging satellite galaxy. The thick disc population is revisited under the light of new data in a number of galactic sample fields. Various thick disc hypotheses are fitted to observational data through a maximum likelihood technique. The resulting characteristics of the thick disc are the following: a scale height of 760 ± 50pc, with a local density of 5.6 ± 1% of the thin disc. The scale length is constrained to be 2.8 ± 0.8kpc, well in agreement with the disc scale length (2.5 ± 0.3kpc). The mean metallicity of the thick disc is found to be -0.7 ±0.2 dex, with no significant metallicity gradients. These photometric constraints in combination with kinematic data give new constraints on the thick disc formation. We show that thick disc characteristics are hardly compatible with a top-down formation scenario but fully compatible with a violent merging event arising at the early thin disc life time as described by Quinn, Hernquist & Fullagar (1993)

The Spiral Structure of the Milky Way, Cosmic Rays, and Ice Age Epochs on Earth

The short term variability of the Galactic cosmic ray flux (CRF) reaching Earth has been previously associated with variations in the global low altitude cloud cover. This CRF variability arises from changes in the solar wind strength. However, cosmic ray variability also arises intrinsically from variable activity of and motion through the Milky Way. Thus, if indeed the CRF climate connection is real, the increased CRF witnessed while crossing the spiral arms could be responsible for a larger global cloud cover and a reduced temperature, thereby facilitating the occurrences of ice ages. This picture has been recently shown to be supported by various data (Shaviv, 2001). In particular, the variable CRF recorded in Iron meteorites appears to vary synchronously with the appearance ice ages. Here we expand upon the original treatment with a more thorough analysis and more supporting evidence. In particular, we discuss the cosmic ray diffusion model which considers the motion of the Galactic spiral arms. We also elaborate on the structure and dynamics of the Milky Way's spiral arms. In particular, we bring forth new argumentation using HI observations which imply that the galactic spiral arm pattern speed appears to be that which fits the glaciation period and the cosmic-ray flux record extracted from Iron meteorites. In addition, we show that apparent peaks in the star formation rate history, as deduced by several authors, coincides with particularly icy epochs, while the long period of 1 to 2 Gyr before present, during which no glaciations are known to have occurred, coincides with a significant paucity in the past star formation rate.Comment: 33 pages, 11 figures. To Appear in New Astronom

L influence du rôle de la femme ayant une activité professionnelle sur la construction des rôles respectifs d homme et de femme chez les adolescents (les conséquences sur la culture coréenne)

Le statut et le rôle des femmes, qui étaient subordonnés dans une structure sociale dominée par les hommes, ont évolué grâce à leur engagement dans une activité professionnelle. Cette évolution entraîne des conflits entre groupes sociaux et des conflits intérieurs chez les femmes elles-mêmes.L activité professionnelle des femmes étend leur rôle à la société, ce qui leur permet de prendre conscience de leur individuation. Cette activité leur confère également un pouvoir économique. Ces deux éléments sont les principaux facteurs de l accélération de l activité professionnelle des femmes en Corée du Sud. Observant cette évolution, les adolescents se font une image positive du rôle professionnel des femmes et projettent une idée des rôles sans discrimination des genres. Cette idée est différente de la conception traditionnelle et montre une facette de l évolution des rôles au fil des générations.Cette recherche analyse l influence de l activité professionnelle des femmes sur la manière dont les adolescents construisent l idée qu ils se font des rôles respectifs des hommes et des femmes. Les résultats permettent de présager de nouveaux rôles pour les femmes en Corée du Sud dans un proche avenir.Cette évolution confère un nouveau statut aux femmes, et ce statut modifie le lien social et familial. Mais il entraîne aussi une évolution de la culture traditionnelle. Le rôle et le statut des femmes ne s appuient plus sur la culture traditionnelle confucéenne. Nous avons finalement pu confirmer que l activité professionnelle des femmes est un facteur principal de l évolution de la culture en Corée du SudThe status and role of women, who are considered subordinate in a social structure dominated by men, has changed thanks to their participation in work. This change has led to a clash between social groups and struggle within the women themselves. Employment broadens women s role in society which raises their awareness of their individuation and gives them economic power. These two elements are major factors in the increase in women in work, in South Korea. By observing this evolution, adolescents can build a positive image of women s professional roles which projects a non-discriminatory impression of the genders. This image is different from the traditional views and shows a facet of how women s roles have evolved through generations.This research analyzes the influence of working women on the way adolescents develop ideas of the role of men and women. The findings enable us to predict new roles for women in South Korea in the near future. Once women are in employment, they become aware of themselves as individuals, capable of breaking free of subordination to male domination. This evolution provides new status to women. This status changes not only family and social links but also the traditional culture. Women s role and status are no longer based on the traditional Confucian culture. Finally, the analysis has confirmed that women s employment is the main factor in the evolution of culture in South KoreaPARIS-DAUPHINE-BU (751162101) / SudocSudocFranceF

Integrating astronomical data and information services at the CDS", this conference

The CDS is providing several unique services to the world-wide astronomical community: the catalogue service, the SIMBAD database, the ALADIN project, bibliography and literature search, yellow pages, etc. We describe how the CDS works at providing a global perspective on astronomical data and information, with the help of recent technological developments.