Full spectral fitting of Milky Way and M31 globular clusters: ages and metallicities

Context: The formation and evolution of disk galaxies are long standing questions in Astronomy. Understanding the properties of globular cluster systems can lead to important insights on the evolution of its host galaxy. Aims: We aim to obtain the stellar population parameters - age and metallicity - of a sample of M31 and Galactic globular clusters. Studying their globular cluster systems is an important step towards understanding their formation and evolution in a complete way. Methods: Our analysis employs a modern pixel-to-pixel spectral fitting technique to fit observed integrated spectra to updated stellar population models. By comparing observations to models we obtain the ages and metallicities of their stellar populations. We apply this technique to a sample of 38 globular clusters in M31 and to 41 Galactic globular clusters, used as a control sample. Results: Our sample of M31 globular clusters spans ages from 150 Myr to the age of the Universe. Metallicities [Fe/H] range from -2.2 dex to the solar value. The age-metallicity relation obtained can be described as having two components: an old population with a flat age-[Fe/H] relation, possibly associated with the halo and/or bulge, and a second one with a roughly linear relation between age and metallicity, higher metallicities corresponding to younger ages, possibly associated with the M31 disk. While we recover the very well known Galactic GC metallicity bimodality, our own analysis of M31's metallicity distribution function (MDF) suggests that both GC systems cover basically the same [Fe/H] range yet M31's MDF is not clearly bimodal. These results suggest that both galaxies experienced different star formation and accretion histories.Comment: A&A, in pres

Synthesis and degradation of poly-β-hydroxybutyrate in a sequencing batch biofilm reactor

The aim of this work was the study of poly-β-hydroxybutyrate (PHB) formation and degradation in a sequencing batch biofilm reactor (SBBR). The SBBR was operated in cycles comprising three individual phases: mixed fill, aeration and draw. A synthetic substrate solution with acetate and ammonium was used. PHB was formed during the aeration phase immediately after acetate depletion, and was subsequently consumed for biomass growth, owing to the high oxygen concentration in the reactor. It was observed a combination of suspended and biofilm growth in the SBBR with predominance of the fixed form of biomass (506 Cmmol and 2102 Cmmol, respectively). Maximum PHB fraction of suspended biomass (0.13 Cmol/Cmol) was considerably higher than that of biofilm (0.01 Cmol/Cmol). This may possibly be explained by a combination of two factors: lower mass transfer limitation of acetate and higher fraction of heterotrophs in suspended biomass compared to the ones of biofilm.Fundo Europeu de Desenvolvimento Regional (FEDER) - POCI 2010 (POCI/AMB/61155/2004)Fundação para a Ciência e a Tecnologia (FCT) - PRAXIS XXI BD/19687/9

Biofilm technology : from support design to reactor operation

The aim of this work was to assess the feasibility of a Sequential Batch Biofilm Reactor (SBBR) to perform carbon and nitrogen removal: from support design to reactor operation. The experimental part was conducted in two phases. In the first phase, different supports were tested to select the most suitable one for SBBR operation. In the second phase, the most appropriate support was used in a SBBR to perform carbon and nitrogen removal. The results demonstrate that the support with the highest internal surface area presented a higher biomass accumulation. Time profiles of nitrogen ions and acetate concentration showed the typical behaviour of a SBBR performing carbon and nitrogen removal. Poly-bhydroxybutyrate (PHB) was formed immediately after acetate depletion and was subsequently consumed for biomass growth, owing to the high oxygen concentration in the reactor

Black hole formation in bidimensional dilaton gravity coupled to scalar matter systems

This work deals with the formation of black hole in bidimensional dilaton gravity coupled to scalar matter fields. We investigate two scalar matter systems, one described by a sixth power potential and the other defined with two scalar fields containing up to the fourth power in the fields. The topological solutions that appear in these cases allow the formation of black holes in the corresponding dilaton gravity models.Comment: Latex, 9 pages. Published in Mod. Phys. Lett. A14 (1999) 268

Morphological transition between diffusion-limited and ballistic aggregation growth patterns

In this work, the transition between diffusion-limited and ballistic aggregation models was revisited using a model in which biased random walks simulate the particle trajectories. The bias is controlled by a parameter $\lambda$, which assumes the value $\lambda=0$ (1) for ballistic (diffusion-limited) aggregation model. Patterns growing from a single seed were considered. In order to simulate large clusters, a new efficient algorithm was developed. For $\lambda \ne 0$, the patterns are fractal on the small length scales, but homogeneous on the large ones. We evaluated the mean density of particles $\bar{\rho}$ in the region defined by a circle of radius $r$ centered at the initial seed. As a function of $r$, $\bar{\rho}$ reaches the asymptotic value $\rho_0(\lambda)$ following a power law $\bar{\rho}=\rho_0+Ar^{-\gamma}$ with a universal exponent $\gamma=0.46(2)$, independent of $\lambda$. The asymptotic value has the behavior $\rho_0\sim|1-\lambda|^\beta$, where $\beta= 0.26(1)$. The characteristic crossover length that determines the transition from DLA- to BA-like scaling regimes is given by $\xi\sim|1-\lambda|^{-\nu}$, where $\nu=0.61(1)$, while the cluster mass at the crossover follows a power law $M_\xi\sim|1 -\lambda|^{-\alpha}$, where $\alpha=0.97(2)$. We deduce the scaling relations \beta=\n u\gamma and $\beta=2\nu-\alpha$ between these exponents.Comment: 7 pages, 8 figure

Impacto das variáveis sociofamiliares no desenvolvimento cognitivo da criança

O presente estudo explora a variável meio (urbano vs rural) no desenvolvimento cognitivo das crianças. A investigação na área aponta que fatores sociofamiliares (profissão da mãe e do pai, habilitações escolares da mãe e do pai e meio de pertença urbano vs rural), assim como os contextos escolares, estão associados a diferenças nas habilidades cognitivas das crianças. Nesta comunicação recorremos à aplicação da Escala de Competências Cognitivas (ECCOs4/10) a uma amostra de crianças com idades compreendidas entre os 6 e os 9 anos, do 1º Ciclo do Ensino Básico, de escolas públicas e privadas, do meio rural e urbano. Esta aplicação da escala procurou analisar as reações e atitudes das crianças em relação a cada uma das provas e aos seus itens, no fundo um estudo mais qualitativo dos processos e estratégias cognitivas que as crianças usam na resolução da ECCOs.Fundação para a Ciência e a Tecnologia (FCT

Spectroscopic binaries in the Solar Twin Planet Search program: from substellar-mass to M dwarf companions

Previous studies on the rotation of Sun-like stars revealed that the rotational rates of young stars converge towards a well-defined evolution that follows a power-law decay. It seems, however, that some binary stars do not obey this relation, often by displaying enhanced rotational rates and activity. In the Solar Twin Planet Search program we observed several solar twin binaries, and found a multiplicity fraction of $42\% \pm 6\%$ in the whole sample; moreover, at least three of these binaries (HIP 19911, HIP 67620 and HIP 103983) clearly exhibit the aforementioned anomalies. We investigated the configuration of the binaries in the program, and discovered new companions for HIP 6407, HIP 54582, HIP 62039 and HIP 30037, of which the latter is orbited by a $0.06$ M$_\odot$ brown dwarf in a 1-month long orbit. We report the orbital parameters of the systems with well-sampled orbits and, in addition, the lower limits of parameters for the companions that only display a curvature in their radial velocities. For the linear trend binaries, we report an estimate of the masses of their companions when their observed separation is available, and a minimum mass otherwise. We conclude that solar twin binaries with low-mass stellar companions at moderate orbital periods do not display signs of a distinct rotational evolution when compared to single stars. We confirm that the three peculiar stars are double-lined binaries, and that their companions are polluting their spectra, which explains the observed anomalies.Comment: 13 pages, 7 figures, accepted for publication in MNRA

Abundance trends in the inner and outer Galactic disk

Based on high-resolution spectra obtained with the MIKE spectrograph on the Magellan telescopes we present detailed elemental abundances for 64 red giant stars in the inner and outer Galactic disk. For the inner disk sample (4-7 kpc from the Galactic centre) we find that stars with both thin and thick disk abundance patterns are present while for Galactocentric distances beyond 10 kpc, we only find chemical patterns associated with the local thin disk, even for stars far above the Galactic plane. Our results show that the relative densities of the thick and thin disks are dramatically different from the solar neighbourhood, and we therefore suggest that the radial scale length of the thick disk is much shorter than that of the thin disk. A thick disk scale-length of L_{thick}=2.0 kpc, and L_{thin}=3.8 kpc for the thin disk, better match the data.Comment: Contributed talk at Galactic archeology, near-field cosmology and the formation of the Milky Way, Shuzenji, Japan, 1-4 November 2011, to be published in ASP Conference Serie

Chemical analysis of eight giant stars of the globular cluster NGC 6366

The metal-rich Galactic globular cluster NGC 6366 is the fifth closest to the Sun. Despite its interest, it has received scarce attention, and little is known about its internal structure. Its kinematics suggests a link to the halo, but its metallicity indicates otherwise. We present a detailed chemical analysis of eight giant stars of NGC 6366, using high resolution and high quality spectra (R > 40000, S/N > 60) obtained at the VLT (8.2 m) and CFHT (3.6 m) telescopes. We attempted to characterize its chemistry and to search for evidence of multiple stellar populations. The atmospheric parameters were derived using the method of excitation and ionization equilibrium of FeI and FeII lines and from those atmospheric parameters we calculated the abundances for other elements and found that none of the elements measured presents star-to-star variation greater than the uncertainties. We compared the derived abundances with those of other globular clusters and field stars available in the literature. We determined a mean [Fe/H] = -0.60 +- 0.03 for NGC 6366 and found some similarity of this object with M 71, another inner halo globular cluster. The Na-O anticorrelation extension is short and no star-to-star variation in Al is found. The presence of second generation stars is not evident in NGC 6366.Comment: 17 pages, 14 figures. Accepted for publication in MNRAS; Corrected typos and added reference

Gains from trans-boundary water quality management in linked catchment and coastal socioecological systems: a case study for the Minho region

Sustainable economic development requires balancing of marginal costs from catchment water pollution abatement and associated marginal benefits from freshwater/coastal ecosystem appreciation. Hence we need to differentiate between intra- and trans-boundary catchments because benefactors and beneficiaries from water quality improvement are not one and the same. In trans-boundary catchments, private (national) welfare maximizing rates of water quality improvement differ across nations as benefits from water quality improvement generally accrue to one nation while the costs are paid by multiple nations. In this paper we develop a deterministic optimal control approach to explore private and social welfare maximizing rates of water pollution abatement in linked catchment and freshwater/coastal socioecological systems. For a case study of the Minho region (Iberian Peninsula), we estimate nation-specific water pollution abatement cost functions (based on management practice adoption) to determine and compare private (national) and social (trans-national) welfare maximizing rates of water pollution abatement. Results show that some private (national) welfare gains can be obtained through adoption of win-win practices, leading to a 12% reduction in the annual rate of water pollution and a 7% increase in annual regional income. Maximum social (international) welfare gains can, however, be obtained through adoption of win-win and lose-win practices across Spain and Portugal, leading to a 36% reduction in water pollution and a 14% increase in regional income. Non-cooperation in water pollution abatement would only lead to a 16%-32% reduction in water pollution and a 8%-13% increase in regional income. Hence, social (trans-national) welfare losses from non-cooperation between Spain and Portugal would equate to between 16 and 81 m€/yr