Analysis of groundwater mining in two carbonate aquifers in Sierra de Estepa (SE Spain) based on hydrodynamic and hydrochemical data

The carbonate aquifers of Lora and Mingo form part of the hydrogeological unit of Sierra de Estepa (SE Spain). By means of time series analysis and a 1D numerical groundwater model, groundwater exploitation was quantified and the mean annual recharge in both systems was estimated (2001–2004). During this period, the Lora and Mingo aquifers received an average groundwater recharge of 0.29 × 10⁶ m³/year and 0.14 × 10⁶ m³/year, respectively, whereas an average of 0.34 × 10⁶ m³/year and 0.21 × 10⁶ m³/year, respectively, was extracted. These conditions led to a conspicuous lowering of the water table in both systems. In addition, the analysis of the evolution of the main hydrogeochemical parameters of the groundwater showed that the increased pumping rates produced an increase in total dissolved solids, and chloride and sodium ions in both aquifers. In the case of the Lora aquifer, the only ion that presented decreased levels was nitrate. The results show that groundwater pumping in both aquifers should not exceed the mean annual recharge of 0.29 × 10⁶ m³/year and 0.14 × 10⁶ m³/year in the Lora and Mingo aquifers, respectively. Nevertheless, it would be advisable to reduce pumping rates to below these values in order to restore piezometric levels and improve groundwater quality for different uses in the future.     

The Herschel PACS photometer calibration

We present a flux calibration scheme for the PACS chopped point-source photometry observing mode based on the photometry of five stellar standard sources. This mode was used for science observations only early in the mission. Later, it was only used for pointing and flux calibration measurements. Its calibration turns this type of observation into fully validated data products in the Herschel Science Archive. Systematic differences in calibration with regard to the principal photometer observation mode, the scan map, are derived and amount to 5 ? 6 %. An empirical method to calibrate out an apparent response drift during the first 300 Operational Days is presented. The relative photometric calibration accuracy (repeatability) is as good as 1 % in the blue and green band and up to 5 % in the red band. Like for the scan map mode, inconsistencies among the stellar calibration models become visible and amount to 2 % for the five standard stars used. The absolute calibration accuracy is therefore mainly limited by the model uncertainty, which is 5 % for all three bands.     

Disc–halo interaction – I. Three-dimensional evolution of the Galactic disc

The results of a three-dimensional model for disc–halo interaction are presented here. The model considers explicitly the input of energy and mass by isolated and correlated supernovae in the disc. Once disrupted by the explosions, the disc never returns to its initial state. Instead it approaches a state where a thin H  i disc is formed in the Galactic plane, overlaid by thick H  i and H  ii gas discs with scaleheights of 500 pc and 1–1.5 kpc, respectively. The upper parts of the thick H  ii disc (the diffuse ionized medium) act as a disc–halo interface, and its formation and stability are directly correlated to the supernova rate per unit area in the simulated disc.     

UV Capabilities to Probe the Formation of Planetary Systems: From the ISM to Planets

Planetary systems are angular momentum reservoirs generated during star formation. Solutions to three of the most important problems in contemporary astrophysics are needed to understand the entire process of planetary system formation: The physics of the ISM. Stars form from dense molecular clouds that contain ∼ 30% of the total interstellar medium (ISM) mass. The structure, properties and lifetimes of molecular clouds are determined by the overall dynamics and evolution of a very complex system – the ISM. Understanding the physics of the ISM is of prime importance not only for Galactic but also for extragalactic and cosmological studies. Most of the ISM volume (∼ 65%) is filled with diffuse gas at temperatures between 3000 and 300 000 K, representing about 50% of the ISM mass. The physics of accretion and outflow. Powerful outflows are known to regulate angular momentum transport during star formation, the so-called accretion–outflow engine. Elementary physical considerations show that, to be efficient, the acceleration region for the outflows must be located close to the star (within 1 AU) where the gravitational field is strong. According to recent numerical simulations, this is also the region where terrestrial planets could form after 1 Myr. One should keep in mind that today the only evidence for life in the Universe comes from a planet located in this inner disk region (at 1 AU) from its parent star. The temperature of the accretion–outflow engine is between 3000 and 10 ⁷ K. After 1 Myr, during the classical T Tauri stage, extinction is small and the engine becomes naked and can be observed at ultraviolet wavelengths. The physics of planet formation. Observations of volatiles released by dust, planetesimals and comets provide an extremely powerful tool for determining the relative abundances of the vaporizing species and for studying the photochemical and physical processes acting in the inner parts of young planetary systems. This region is illuminated by the strong UV radiation field produced by the star and the accretion–outflow engine. Absorption spectroscopy provides the most sensitive tool for determining the properties of the circumstellar gas as well as the characteristics of the atmospheres of the inner planets transiting the stellar disk. UV radiation also pumps the electronic transitions of the most abundant molecules (H ₂, CO, etc.) that are observed in the UV.Here we argue that access to the UV spectral range is essential for making progress in this field, since the resonance lines of the most abundant atoms and ions at temperatures between 3000 and 300 000 K, together with the electronic transitions of the most abundant molecules (H ₂, CO, OH, CS, S ₂, CO ₂ ⁺, C ₂, O ₂, O₃, etc.) are at UV wavelengths. A powerful UV-optical instrument would provide an efficient mean for measuring the abundance of ozone in the atmosphere of the thousands of transiting planets expected to be detected by the next space missions (GAIA, Corot, Kepler, etc.). Thus, a follow-up UV mission would be optimal for identifying Earth-like candidates.     

Pressure dependence of the lattice dynamics of diaspore, α-AlO(OH), from Raman spectroscopy and density functional perturbation theory

We have measured the pressure-induced change in the lattice dynamics of diaspore, α-AlO(OH), by in situ Raman spectroscopy up to 25 GPa. The spectra are evaluated by density functional perturbation theory-based atomistic model calculations. The assignment of calculated to experimentally observed Raman bands is based on the calculation of Raman intensities. We discuss the accuracy of the approach employed for these calculations and explain the relative magnitudes of mode Grüneisen parameters.     

Long-term resilience, bush encroachment patterns and local knowledge in a Northeast African savanna

Bush encroachment is a significant phenomenon in savanna environments as it affects wildlife and local livelihoods by preventing new pasture generation. In this article we present a 2000-year record of vegetation change in the Dara range of the Mago National Park, southwestern Ethiopia, an area inhabited by Mursi agro-pastoralists. We use an interdisciplinary approach to understand whether bush encroachment in this area is a recent event or a transitional state of the savanna and describe the local understanding of encroachment as a species-specific process. The vegetation record was obtained from a fossil hyrax midden, a type of sediment already used in Southern Africa but never before in East Africa. Six encroaching phases, led by Capparaceae and Grewia, were found over the last two millennia. The system proved to be resilient, with alternating open and encroached phases, and showed a non-linear response to environmental change, thereby fitting the control theory hypothesis for hysteresis loops. Determining the thresholds conditioning the system's resilience could help to improve savanna management for both local people and National Park authorities.     

On the initial cluster mass distribution inferred from synthesis models

In this contribution we examine the problem of inferring ages and initial cluster masses from synthesis models at the limit of low-mass clusters (M≤ a few ×10⁴ M_⊙). We show that it is not possible to apply directly synthesis models using standard methods to such clusters, since the basic hypothesis implicit in the models (a fixed proportionality between the number of stars in different evolutionary phases) is not fulfilled due to an insufficient number of stars for a reliable sampling of the stellar initial mass function. The consequence of this incomplete sampling is a non-Gaussian distribution of the mass–luminosity relation for clusters that share the same evolutionary conditions (age, metallicity and stellar initial mass distribution function). We review some tests, that can be performed before the start of the analysis, to estimate if the observed cluster can be analyzed with synthesis models following traditional procedures (like χ ² minimization) or if it is necessary make use of synthesis models in a probabilistic framework. Finally, we show the implications of these results for estimating the low-mass tail in the initial cluster mass distribution function.