Carbon Stars and other Luminous Stellar Populations in M33

The M33 galaxy is a nearby, relatively metal-poor, late-type spiral. Its proximity and almost face-on inclination means that it projects over a large area on the sky, making it an ideal candidate for wide-field CCD mosaic imaging. Photometry was obtained for more than 10^6 stars covering a 74' x 56' field centered on M33. Main sequence (MS), supergiant branch (SGB), red giant branch (RGB) and asymptotic giant branch (AGB) populations are identified and classified based on broad-band V and I photometry. Narrow-band filters are used to measure spectral features allowing the AGB population to be further divided into C and M-star types. The galactic structure of M33 is examined using star counts, colour-colour and colour-magnitude selected stellar populations. We use the C to M-star ratio to investigate the metallicity gradient in the disk of M33. The C/M-star ratio is found to increase and then flatten with increasing galactocentric radius in agreement with viscous disk formation models. The C-star luminosity function is found to be similar to M31 and the SMC, suggesting that C-stars should be useful distance indicators. The ``spectacular arcs of carbon stars'' in M33 postulated recently by Block et al. (2004) are found in our work to be simply an extension of M33's disk.Comment: 20 pages, 20 figures. Accepted for publication in The Astronomical Journa

Implantação, manejo e utilização do sistema agroflorestal cercas vivas de Gliricidia sepium (Jacq.) Steud. na Costa Rica.

O melhor aproveitamento de agroecossistemas pouco produtivos, para a racionalização no uso da terra e a identificação de espécies para usos múltiplos, que cumpram objetivos sócio-econômicos e ecológicos, são aspectos que justificam esse trabalho. Efetuou-se um levantamento, a nível de Costa Rica, com o intuito de codificar o conhecimento dos agricultores quanto aos fatores que influem na implantação, manejo e utilização das cercas vivas de Gliricidia sepium. Foram selecionadas cinco zonas ecológicas para o levantamento, nas quais também se tomaram amostras de partes vegetais para análises físico-químicas. Para a implantação das cercas vivas, as atividades objetivam a máxima taxa de sobrevivência das estacas. Os aspectos mais importantes são: estado fisiológico das árvores para o corte, idade e dimensões das estacas, profundidade de plantio e fixação dos arames. A poda periódica é fundamental para a manutenção e uso adequado na produção de estacas, lenha e proteção contra o vento. A espécie não é utilizada plenamente pelos agricultores, sendo possível um aumento dos produtos e serviços. A análise dos tecidos detectou que as folhas contém maior quantidade de N, P e Ca, em comparação com os talos tenros. Nos casos de K e Mg, não houve diferença entre partes vegetais. Pela quantidade de proteína bruta ( X = 26,8%) e valores da digestibilidade in vitro ( X = 66,6%), as folhas de Gliricidia são adequadas para uso como forragem. O potencial da espécie para produção de biomassa nas cercas vivas justifica pesquisas que determinem sua capacidade em regime de cortes sucessivos

Searching for tidal tails around ω\omega Centauri using RR Lyrae Stars

We present a survey for RR Lyrae stars in an area of 50 deg$^2$ around the globular cluster $\omega$ Centauri, aimed to detect debris material from the alleged progenitor galaxy of the cluster. We detected 48 RR Lyrae stars of which only 11 have been previously reported. Ten among the eleven previously known stars were found inside the tidal radius of the cluster. The rest were located outside the tidal radius up to distances of $\sim 6$ degrees from the center of the cluster. Several of those stars are located at distances similar to that of $\omega$ Centauri. We investigated the probability that those stars may have been stripped off the cluster by studying their properties (mean periods), calculating the expected halo/thick disk population of RR Lyrae stars in this part of the sky, analyzing the radial velocity of a sub-sample of the RR Lyrae stars, and finally, studying the probable orbits of this sub-sample around the Galaxy. None of these investigations support the scenario that there is significant tidal debris around $\omega$ Centauri, confirming previous studies in the region. It is puzzling that tidal debris have been found elsewhere but not near the cluster itself.Comment: 11 pages, 11 figures, Accepte

Hardy spaces for a class of singular domains

We set a framework for the study of Hardy spaces inherited by complements of analytic hypersurfaces in domains with a prior Hardy space structure. The inherited structure is a filtration, various aspects of which are studied in specific settings. For punctured planar domains, we prove a generalization of a famous rigidity lemma of Kerzman and Stein. A stabilization phenomenon is observed for egg domains. Finally, using proper holomorphic maps, we derive a filtration of Hardy spaces for certain power-generalized Hartogs triangles, although these domains fall outside the scope of the original framework