Weak gravitational shear and flexion with polar shapelets

We derive expressions, in terms of 'polar shapelets', for the image distortion operations associated with weak gravitational lensing. Shear causes galaxy shapes to become elongated, and is sensitive to the second derivative of the projected gravitational potential along their line of sight; flexion bends galaxy shapes into arcs, and is sensitive to the third derivative. Polar shapelets provide a natural representation, in which both shear and flexion transformations are compact. Through this tool, we understand progress in several weak lensing methods. We then exploit various symmetries of shapelets to construct a range of shear estimators with useful properties. Through an analogous investigation, we also explore several flexion estimators. In particular, some of the estimators can be measured simultaneously and independently for every galaxy, and will provide unique checks for systematics in future weak lensing analyses. Using simulated images from the Shear TEsting Programme, we show that we can recover input shears with no significant bias. A complete software package to parametrize astronomical images in terms of polar shapelets, and to perform a full weak lensing analysis, is available on the Internet.     

Modelling the habitat suitability of cetaceans: Example of the sperm whale in the northwestern Mediterranean Sea

Cetaceans are mobile and spend long periods underwater. Because of this, modelling their habitat could be subject to a serious problem of false absence. Furthermore, extensive surveys at sea are time and money consuming, and presence–absence data are difficult to apply. This study compares the ability of two presence–absence and two presence-only habitat modelling methods and uses the example of the sperm whale (Physeter macrocephalus) in the northwestern Mediterranean Sea. The data consist of summer visual and acoustical detections of sperm whales, compiled between 1998 and 2005. Habitat maps were computed using topographical and hydrological eco-geographical variables. Four methods were compared: principal component analysis (PCA), ecological niche factor analysis (ENFA), generalized linear model (GLM) and multivariate adaptive regression splines (MARS). The evaluation of the models was achieved by calculating the receiver operating characteristic (ROC) of the models and their respective area under the curve (AUC). Presence–absence methods (GLM, AUC=0.70, and MARS, AUC=0.79) presented better AUC than presence-only methods (PCA, AUC=0.58, and ENFA, AUC=0.66), but this difference was not statistically significant, except between the MARS and the PCA models. The four models showed an influence of both topographical and hydrological factors, but the resulting habitat suitability maps differed. The core habitat on the continental slope was well highlighted by the four models, while GLM and MARS maps also showed a suitable habitat in the offshore waters. Presence–absence methods are therefore recommended for modelling the habitat suitability of cetaceans, as they seem more accurate to highlight complex habitat. However, the use of presence-only techniques, in particular ENFA, could be very useful for a first model of the habitat range or when important surveys at sea are not possible.     

Weak lensing of the CMB by large-scale structure

Several recent papers have studied lensing of the CMB by large-scale structures, which probes the projected matter distribution from z=10³ to z0. This interest is motivated in part by upcoming high resolution, high sensitivity CMB experiments, such as APEX/SZ, ACT, SPT or Planck, which should be sensitive to lensing. In this paper, we examine the reconstruction of the large-scale dark matter distribution from lensed CMB temperature anisotropies. We go beyond previous work in using numerical simulations to include higher order, non-Gaussian effects and find that the convergence and its power spectrum are biased, with the bias increasing with the angular resolution. We also study the contamination by the kinetic Sunyaev–Zel'dovich signal, which is spectrally indistinguishable from lensed CMB anisotropies, and find that it leads to an overestimate of the convergence. We finish by estimating the sensitivity of the previously cited experiments and find that all of them could detect the lensing effect, but would be biased at around the 10% level.     

http://www.sciencedirect.com/science/article/pii/S1674987113000315

The Panzhihua gabbroic intrusion,part of the plumbing system of the Emeishan large igneous province, intruded late-Proterozoic dolomites and marls about～263 Ma ago.The dolomites in the contact aureole were converted to brucite marbles and a diverse suite of forsterite,diopside and garnet skarns.The variation in mineralogy is explained in part by differences in the composition of the protolith,particularly the proportion of silica minerals and clay,and in part by transfer of elements from intruding magmas.The trace element compositions of most marbles and skarns are very similar to those of unmetamorphosed dolomites and marls,but some contain high Si,Ti,and Fe contents that are interpreted to have come from a magmatic source.Three brucite marbles sampled～10 m from the contact of the intrusion and named "enriched brucite marble" have trace element compositions very different from their dolomitic protolith:their rare earth elements are strongly enriched whereas levels of Nb-Ta,Zr-Hf and Ti are very low.These characteristics resemble those of carbonate liquid in equilibrium with silicate liquid or more probably with silicate minerals in the case of Panzhihua,a similarity we take to indicate that the sample underwent partial melting.Samples taken up to 300 m from the contact contain brucite indicating that high temperatures persisted well into the country rocks.However,other samples collected only tens of metres from the contact are only slightly recrystallized indicating that conditions in the aureole were highly variable.We suggest that temperatures within the aureole were controlled by conduction of heat from the main intrusion and by supply of additional heat from abundant small dykes within the aureole.Circulation of fluids derived from deeper levels in the aureole flushed the carbon dioxide from the dolomite,lowering temperature needed to partially melt carbonate to the temperatures attained near the intrusion.Irregular but extensive heating destabilized the carbonates of the aureole and decarbonation reactions associated with carbonate breakdown and melting emitted a large volume of CO₂,with potential impact on global climate.     

Environmental fragility evaluation and guidelines for environmental zoning: a study case on Ibiuna (the Southeastern Brazilian region)

Environmental fragility models are important decision tools for policy makers as they help quantify environmental sensitivity and understand the relationship between human activities and environmental quality. The objective of this study was to evaluate three different environmental fragility models within the Brazilian rainforest region and to use the results to develop environmental zone classes. Two rural river basins located in Ibiuna, Sao Paulo state, Brazil, were studied. Input variables, including slope class, relief dissection rate, soil class, lithology, land cover, and climate data, were used to compute environmental fragility classes using three standard models. The model outputs were evaluated on their ability to accurately predict the most sensitive and least sensitive areas. The best models for each region were used to derive environmental zoning maps, including restoration priorities, best regions for agriculture, and areas with high needs for soil management. These maps will help support land use strategies for environmental restoration. This study provides insight into territorial ordering and management of environmental services with a regional perspective.     

Extragalactic science with the FRESNEL imager

The space Fresnel Interferometric Imager, originally proposed to the ESA Cosmic Vision plan, is an innovative concept providing enhanced capabilities in terms of spatial resolution and dynamical range. In this paper we describe some of the most promising applications of the Fresnel Interferometric Imager concept in extragalactic studies. There are two different topics where the FII could make major progress. The first one is the mapping of star-formation in galaxies, from the local universe to ??75?C85% look back time, based on the first version of FII which is optimized for the UV and optical domains. The second topic is a test case for a subsequent improved version of FII, with a larger collecting area and optimized for the near-IR, focusing on the physical properties of the first galaxies.