Infrared studies of the structure of the galaxy

A simple three-component model of the Galaxy is presented. The Galaxy is represented by (1) a disk whose stellar density decreases exponentially with distance from the galactic centre as well as perpendicularly as a function of height above or below the galactic plane; plus a (2) ring with a radius of R₀sin25 kpc considered to be an enhancement of the disk and finally by (3) an oblate de Vaucouleurs spheroid meant to represent the galactic bulge. The absorbing material is also assumed to be distributed as an exponential layer. The model is used to fit the 2.4 μm integrated flux observations of the Galaxy, which it does remarkably well, and to determine some of the model constants such as the radial length scale for the disk and the central densities for the bulge and ring components. Based on this model and the derived values of the constants, a series of stellar count predictions for the Km agnitude (2.2 μm) were made. These predictions were com pared to those made by the Bahcall and Soneira model of the Galaxy. The model predicts an almost complete dominance of the bright K-magnitude (K ≤ 14-15) realm by the disk population. At fainter magnitudes the bulge population dominates. A transition region at which disk and bulge contributions are similar occurs at different K -m agnitudes and depends on galactic longitude (from K ~ +9.5 at l ~ 0 to K ~ +20 at l ~ 180). Stellar counts along the galactic plane in the range 220 ≤ l ≤ 60 have been obtained, and have been fitted to the galactic model described above. The model constants utilised in fitting the stellar counts are those derived from the model fit to the 2.4 μm observed integrated flux. Considering the general nature of the model (same constants for all regions), the agreement between the model predictions and the observations is remarkable. The slight discrepancies which have arisen between theory and observations have been interpreted, in most cases, as inhomogeneities in the absorbing material. In the longitude range 0 ≤ l ≤ 60, there appears to be a slight theoretical excess over the observed counts at bright magnitudes. A carefully chosen alteration of the absolute K-magnitude of all the stars in the Luminosity Function (LF) may be necessary to produce a perfect fit between predicted and observed Cumulative Counts Functions (CCF’s). A low absorption window in the direction l — 0, 6 ~ -4, known as Baade’s Window (BW) has been observed photometrically as well as spectroscopically. A K-scan of this region provided an observational CCF which, with the aid of the model discussed above, was decomposed into possible disk plus bulge contributions. The following results were obtained: • At bright K-magnitudes the slope of the disk CCF is different from that of the bulge CCF. This suggests the presence of two radically different stellar populations within a radius of ± 3 kpc from the galactic centre. • Possible similarities between the real BW bulge population and globular clusters stars is suggested from the similar slope of both stellar populations’ CCF’s. • A significant spread in the (J-H) vs. (H-K), as well as in the CO vs. (J-K) diagram suggests an intrinsic spread in the colour of the sources, which may indicate a possible spread in the metallicity of the objects observed in BW. • What may be identified as the brightest infrared (IR) magnitude locus for stars in BW, is composed of young (2 x 10⁹ years) Asymptotic Giant Branch (AGB) stars with a luminosity of the order ~ 10⁴Lʘ. • In BW ‘true’ bulge members appear to be CO-poor as opposed to ‘true’ disk members which seem to have higher CO-index values. This suggests there is a difference in metallicity of the stars in the disk and the bulge. ‘True’ bulge members appear to be more metal poor than 47-Tuc. There is a hint of kinematical differences between CO-weak and CO-strong stars which is consistent with our picture of ‘true’ bulge and ‘true’ disk populations respectively. Further photometric, spectroscopic and kinematical studies of IR sources in low absorption regions will help to confirm the points put forward in this thesis

Sub-arcsecond radio and optical observations of the likely counterpart to the gamma-ray source 2FGL J2056.7+4939

We have searched and reviewed all multi- wavelength data available for the region towards the gamma-ray source 2FGL J2056.7+4939 in order to con- strain its possible counterpart at lower energies. As a result, only a point-like optical/infrared source with flat-spectrum radio emission is found to be consistent with all X-ray and gamma-ray error circles. Its struc- ture is marginally resolved at radio wavelengths at the sub-arcsecond level. An extragalactic scenario appears to be the most likely interpretation for this object.Comment: 5 pages, 3 figures, 1 tabl

A major star formation region in the receding tip of the stellar Galactic bar

We present an analysis of the optical spectroscopy of 58 stars in the Galactic plane at $l=27$\arcdeg, where a prominent excess in the flux distribution and star counts have been observed in several spectral regions, in particular in the Two Micron Galactic Survey (TMGS) catalog. The sources were selected from the TMGS, to have a $K$ magnitude brighter than +5 mag and be within 2 degrees of the Galactic plane. More than 60% of the spectra correspond to stars of luminosity class I, and a significant proportion of the remainder are very late giants which would also be fast evolving. This very high concentration of young sources points to the existence of a major star formation region in the Galactic plane, located just inside the assumed origin of the Scutum spiral arm. Such regions can form due to the concentrations of shocked gas where a galactic bar meets a spiral arm, as is observed at the ends of the bars of face-on external galaxies. Thus, the presence of a massive star formation region is very strong supporting evidence for the presence of a bar in our Galaxy.Comment: 13 pages (latex) + 4 figures (eps), accepted in ApJ Let

Simultaneous multiwavelength observations of the Low/Hard State of the X-ray transient source SWIFT J1753.5-0127

We report the results of simultaneous multiwavelength observations of the X-ray transient source SWIFT J1753.5-0127 performed with INTEGRAL, RXTE, NTT, REM and VLA on 2005 August 10-12. The source, which underwent an X-ray outburst since 2005 May 30, was observed during the INTEGRAL Target of Opportunity program dedicated to new X-ray novae located in the Galactic Halo. Broad-band spectra and fast timing variability properties of SWIFT J1753.5-0127 are analyzed together with the optical, near infra-red and radio data. We show that the source was significantly detected up to 600 keV with Comptonization parameters and timing properties typical of the so-called Low/Hard State of black hole candidates. We build a spectral energy distribution and we show that SWIFT J1753.5-0127 does not follow the usual radio/X-ray correlation of X-ray binaries in the Low/Hard State. We give estimates of distance and mass. We conclude that SWIFT J1753.5-0127 belongs to the X-ray nova class and that it is likely a black hole candidate transient source of the Galactic Halo which remained in the Low/Hard State during its main outburst. We discuss our results within the context of Comptonization and jet models.Comment: Accepted for publication in ApJ, 25 pages, 4 tables, 11 figures (3 in color

Valoração econômica dos serviços ambientais em um sistema agrossilvipastoril no bioma caatinga.

Resumo: No intuito de minimizar os impactos da ação antrópica sobre o bioma Caatinga, a Embrapa Caprinos e Ovinos desenvolveu um sistema agroflorestal (SAF) para o semiárido que oferece benefícios ao sistema produtivo bem como serviços ambientais. O objetivo deste trabalho foi valorar o serviço ambiental - sequestro de carbono, gerado por um SAF localizado em Sobral/CE. Para isso, foram desenvolvidos os índices de contribuição (IC), o custo de oportunidade das atividades agropecuárias desenvolvidas na agricultura familiar do Ceará (CO) e a construção do índice-ponto (IP) obtido na área. A valoração foi feita pela multiplicação entre o IP e o CO indexado à Unidade Fiscal de Referência do Ceará (UFIRCE). O custo de oportunidade foi de R$878,36. O SAF obteve índice-ponto igual à 5.4, equivalente ao valor de R$ 4.743,82, sendo o valor de R$592,98 quando avaliado por hectare. A metodologia de valoração econômica proposta se mostrou eficiente e eficaz em responder ao objetivo da pesquisa e serve como base para um processo de pagamento pelos serviços ambientais (PSA) [Economic valuation of environmental services on a agrossilvipastoral system of “caatinga” biome]. In order to minimize the impacts of human action on the “Caatinga” biome, Embrapa developed a agroforestry system (SAF) for semi arid areas that provide benefits to the productive system and environmental services. The objective of this study was to find a value for environmental services - carbon sequestration, generated by a SAF located in Sobral, CE. Thus, were developed contribution rates (IC), the opportunity cost of agricultural activities developed in family farming in Ceará (CO) and the construction of the index-point (IP) obtained in the area. The valuation was done by multiplying the IP and CO indexed to the Fiscal Reference Unit of Ceará (UFIRCE). The opportunity cost was U$535.9. This index obtained SAF-point equal to 5.4, equivalent to U$2892.57, and the value of U$361.57 when measured per hectare. The economic valuation methodology proposed is efficient and effective in responding to our research and serves as the basis for a process of payment for environmental services (PES

Democracia (im)pactada : coaliciones políticas en Bolivia (1985-2003)

El balance de José Luis Exeni Rodríguez acerca de la democracia pactada permite distinguir las experiencias positivas y negativas del pasado para encarar el desafío permanente de la ampliación de la democracia sin debilitar su cualidad hegemónica, aquella que la convierte en la mejor forma de gobierno. Una idea que se refuerza con la interpretación que el autor propone sobre un período político mediante un recorrido analítico matizado con claridad conceptual, precisión metodológica y exquisito estilo narrativo. Un libro que invita a reflexionar críticamente sobre la democracia y estimula una lectura placentera del análisis político. Del Prólogo de Fernando Mayorg

Application of molecular topology to the prediction of antimalarial activity of 4-anilinoquinoline analogues

La malaria es una enfermedad parasitaria causada por protozoos del género Plasmodium y transmitida por vectores del género Anopheles . En 2019 esta enfermedad se cobró la vida de más de 400.000 personas, de las cuales un 94 % se concentraban en la región de África. Uno de los principales problemas en el control de la malaria es la aparición de resistencias frente a los diferentes fármacos que existen, es por ello que es necesario el desarrollo de alternativas antimaláricas eficaces. En este estudio se ha aplicado la topología molecular a una serie de compuestos análogos de la 4-anilinoquinolina con actividad inhibitoria de la proliferación de 3 cepas de Plasmodium falciparum, una sensible a la cloroquina (D6) y dos resistentes (W2 y C235); para así desarrollar un modelo de relación cuantitativa estructura-actividad QSAR que permita predecir la actividad de los compuestos frente a cada una de ellas. Utilizando el análisis lineal discriminante se seleccionaron tres funciones que clasificaron correctamente el 87 % de los compuestos analizados en la cepa D6, en la W2 y en la C235, respectivamente. Para la validación del modelo se empleó un test interno del tipo leave some out para cada una de las funciones. Por último, se aplicó el modelo en la búsqueda de nuevos compuestos antimaláricos potencialmente activos frente a las tres cepas.Malaria is a parasitic disease caused by the Plasmodium protozoa and transmitted by vector of the genus Anopheles . In 2019, this disease claimed the lives of more than 400.000 people, of which 94 % are concentrated in the African region. One of the main problems with malaria control is parasite resistance to the different drugs that exist, which is why it is necessary to develop effective antimalarial alternatives. In this study, molecular topology was applied to 4-anilinoquinoline analogs with proliferation inhibitory activity of 3 Plasmodium falciparum strains, one chloroquine sensitive (D6) and two chloroquine resistant (W2 and C235); in order to develop a quantitative structure-activity (QSAR) model to predict the activity of the compounds against each of them. Using linear discriminant analysis, three functions were selected that correctly classified 87 % of the compounds analyzed in strain D6, W2 and C235, respectively. The leave some out test was carried out to validate this model. Finally, the model was applied to search for new antimalarial compounds potentially active against all three strains.Ciencias Experimentale