The Age Dependent Luminosities of the Red Giant Branch Bump, Asymptotic Giant Branch Bump, and Horizontal Branch Red Clump

Color-magnitude diagrams of globular clusters often exhibit a prominent horizontal branch (HB) and may also show features such as the red giant branch (RGB) bump and the asymptotic giant branch (AGB) bump. Stellar evolution theory predicts that the luminosities of these features will depend on the metallicity and age of the cluster. We calculate theoretical lines of 2 to 12 Gyr constant age RGB-bumps and AGB-bumps in the V(HB-Bump)--[Fe/H] diagram, which shows the brightness difference between the bump and the HB as a function of metallicity. In order to test the predictions, we identify giant branch bumps in new Hubble Space Telescope color-magnitude diagrams for 8 SMC clusters. First, we conclude that the SMC cluster bumps are RGB-bumps. The data for clusters younger than ~6 Gyr are in fair agreement the relative age dependent luminosities of the HB and RGB-bump. The V(HB-Bump)--[Fe/H] data for clusters older then ~6 Gyr demonstrate a less satisfactory agreement with our calculations. We conclude that ~6 Gyr is a lower bound to the age of clusters for which the Galactic globular cluster, age independent V(HB-Bump)--[Fe/H] calibration is valid. Application of the V(HB-bump)--[Fe/H] diagram to stellar population studies is discussed.Comment: Accepted for publication in the Astrophysical Journal, 30 pages, Latex aaspp4.sty, including 7 postscript figure

3D gravity and non-linear cosmology

By the inclusion of an additional term, non-linear in the scalar curvature $R$, it is tested if dark energy could rise as a geometrical effect in 3D gravitational formulations. We investigate a cosmological fluid obeying a non-polytropic equation of state (the van der Waals equation) that is used to construct the energy-momentum tensor of the sources, representing the hypothetical inflaton in gravitational interaction with a matter contribution. Following the evolution in time of the scale factor, its acceleration, and the energy densities of constituents it is possible to construct the description of an inflationary 3D universe, followed by a matter dominated era. For later times it is verified that, under certain conditions, the non-linear term in $R$ can generate the old 3D universe in accelerated expansion, where the ordinary matter is represented by the barotropic limit of the van der Waals constituent.Comment: 7 pages, to appear in Mod. Phys. Let

Non-linear terms in 2D cosmology

In this work we investigate the behavior of two-dimensional (2D) cosmological models, starting with the Jackiw-Teitelboim (JT) theory of gravitation. A geometrical term, non-linear in the scalar curvature $R$, is added to the JT dynamics to test if it could play the role of dark energy in a 2D expanding universe. This formulation makes possible, first, the description of an early (inflationary) 2D universe, when the van der Waals (vdW) equation of state is used to construct the energy-momentum tensor of the gravitational sources. Second, it is found that for later times the non-linear term in $R$ can generate an old 2D universe in accelerated expansion, where an ordinary matter dominated era evolves into a decelerated/accelerated transition, giving to the dark energy effects a geometrical origin. The results emerge through numerical analysis, following the evolution in time of the scale factor, its acceleration, and the energy densities of constituents.Comment: tex file plus figures in two zipped files. To appear in Europhys. Let

The VISTA Orion mini-survey: star formation in the Lynds 1630 North cloud

The Orion cloud complex presents a variety of star formation mechanisms and properties and it is still one of the most intriguing targets for star formation studies. We present VISTA/VIRCAM near-infrared observations of the L1630N star forming region, including the stellar clusters NGC 2068 and NGC 2071, in the Orion molecular cloud B and discuss them in combination with Spitzer data. We select 186 young stellar object (YSO) candidates in the region on the basis of multi-colour criteria, confirm the YSO nature of the majority of them using published spectroscopy from the literature, and use this sample to investigate the overall star formation properties in L1630N. The K-band luminosity function of L1630N is remarkably similar to that of the Trapezium cluster, i.e., it presents a broad peak in the range 0.3-0.7 M$_\odot$ and a fraction of sub-stellar objects of $\sim$20%. The fraction of YSOs still surrounded by disk/envelopes is very high ($\sim$85%) compared to other star forming regions of similar age (1-2 Myr), but includes some uncertain corrections for diskless YSOs. Yet, a possibly high disk fraction together with the fact that 1/3 of the cloud mass has a gas surface density above the threshold for star formation ($\sim$129 M$_\odot$ pc$^{-2}$), points towards a still on-going star formation activity in L1630N. The star formation efficiency (SFE), star formation rate (SFR) and density of star formation of L1630N are within the ranges estimated for galactic star forming regions by the Spitzer "core to disk" and "Gould's Belt" surveys. However, the SFE and SFR are lower than the average value measured in the Orion A cloud and, in particular, lower than that in the southern regions of L1630. This might suggest different star formation mechanisms within the L1630 cloud complex.Comment: 22 pages, 9 figure

Avaliação do desempenho reprodutivo do rebanho leiteiro do Estado de Rondônia: formação e gestão de banco de dados.

Para que o produtor se adapte aos novos moldes de produção, um intenso controle sobre os dados do rebanho deve ser empregado nos sistemas de produção de leite. Além de produzir com eficiência, sustentabilidade ambiental, responsabilidade social e sem desperdícios é preciso desenvolver habilidades no gerenciamento e motivação de pessoas para comprar insumos, na venda da produção e na gestão adequada dos custos. Desta forma, há necessidade que o produtor desenvolva ferramentas e práticas de monitoramento de seus dados para processar, interpretar e transformá–los em informação. Vários fatores afetam o registro e gestão dos dados da fazenda. O efetivo uso de registros representa um “divisor de águas” na medicina moderna do gado de leite. A coleta de dados permite a definição de valores-referência (benchmarks), padrões, níveis de interferência e objetivos. Os registros proveem acesso aos resultados de performance do rebanho e, quando surgem os problemas, servem como a maior fonte de informação para o diagnóstico. Como a produção de leite tem aumentado consideravelmente na maioria das bacias leiteiras do Brasil, os profissionais “de campo” devem estar cada vez mais dedicados à análise e organização dos dados de produção.bitstream/item/57917/1/doc142-rebanholeiteiro.pd