Integrating Discrete and Continuous Data in an OpenGeospatial‐Compliant Specification

The integrated management of heterogeneous spatial data, such as continuous fields and discrete data, is an important issue for the Geographic Information (GI) community. Indeed, GI users are forced to navigate among and operate with several tools in order to solve their spatial problems, due to the lack of systems capable of integrating different components, each meant to provide a specific solution. The aim of this article is to propose an OpenGeospatial‐compliant solution which supports expert users in handling problems involving heterogeneous data by means of a seamless approach. A class hierarchy modeling spatial discrete objects, continuous data, relationships, and operations, is described, whereby data are organized in agreement with the binary representation. A running example is illustrated to support readers' understanding of the proposed solution. Finally, some guidelines about an implementation modality are given, to demonstrate the applicability of the proposal to an existing DBMS.     

Decoding the spectra of SDSS early-type galaxies: new indicators of age and recent star formation

We apply principal component analysis (PCA) to a sample of early-type galaxies from the Sloan Digital Sky Survey (SDSS) in order to infer differences in their star formation histories from their unresolved stellar populations. We select a   z < 0.1  volume-limited sample comprising ∼7000 early-type galaxies from SDSS/Data Release 4. Out of the first few principal components (PC), we study four which give information about stellar populations and velocity dispersion. We construct two parameters (η and ζ) as linear combinations of PC1 and PC2. The four components can be presented as 'optimal filters' to explore in detail the properties of the underlying stellar populations. By comparing various photospectroscopic observables – including near-ultraviolet (NUV) photometry from Galaxy Evolution Explorer (GALEX) – we find ζ to be most sensitive to recent episodes of star formation, and η to be strongly dependent on the average age of the stellar populations. Both η and ζ also depend on metallicity. We apply these optimal filters to composite spectra assembled by Bernardi et al. The distribution of the η component of the composites appear to be indistinguishable between high- and low-density regions, whereas the distribution of ζ parameters have a significant skew towards lower values for galaxies in low-density regions. This result suggests that galaxies in lower density environments are less likely to present weak episodes of recent star formation. In contrast, a significant number of galaxies from our high-density subsample – which includes clusters (both outer regions and centres) and groups – underwent small but detectable recent star formation at high metallicity, in agreement with recent estimates targeting elliptical galaxies in Hickson Compact Groups and in the field.     

Comparison of the ENEAR peculiar velocities with the PSCz gravity field

We present a comparison between the peculiar velocity field measured from the ENEAR all-sky D _n– σ catalogue and that derived from the galaxy distribution of the IRAS Point Source Catalog Redshift Survey (PSC z ). The analysis is based on a modal expansion of these data in redshift space by means of spherical harmonics and Bessel functions. The effective smoothing scale of the expansion is almost linear with redshift reaching 1500 km s⁻¹ at 3000 km s⁻¹. The general flow patterns in the filtered ENEAR and PSC z velocity fields agree well within 6000 km s⁻¹, assuming a linear biasing relation between the mass and the PSC z galaxies. The comparison allows us to determine the parameter     where Ω is the cosmological density parameter and b is the linear biasing factor. A likelihood analysis of the ENEAR and PSC z modes yields     in good agreement with values obtained from Tully–Fisher surveys.     

Sediments from Lake Cheko (Siberia), a possible impact crater for the 1908 Tunguska Event

Cheko, a small lake located in Siberia close to the epicentre of the 1908 Tunguska explosion, might fill a crater left by the impact of a fragment of a Cosmic Body. Sediment cores from the lake’s bottom were studied to support or reject this hypothesis. A 175‐cm long core, collected near the center of the lake, consists of an upper ～1 m thick sequence of lacustrine deposits overlaying coarser chaotic material. ²¹⁰Pb and ¹³⁷Cs indicate that the transition from lower to upper sequence occurred close to the time of the Tunguska Event. Pollen analysis reveals that remains of aquatic plants are abundant in the top post‐1908 sequence, but are absent in the lower pre‐1908 portion of the core. These results, including organic C, N and δ¹³C data, suggest that Lake Cheko formed at the time of the Tunguska Event.     

巴西Ara(c)uaí河流域长期水量平衡分析

Semi-arid and arid areas exhibit great temporal variability in water availability. In some of these regions, a one- or two-day rainfall is followed by intervening dry periods of variable length. In recent decades, many rivers of the semi-arid portion of the Jequitinhonha Basin have been undergoing a progressive discharge reduction, mainly of their base flow, the are presented herein. Satellite images, hydrometeorological and river discharge data were analyzed; mean and variance tests were conducted to determine temporal homogeneity.Historical pluviometric data analysis shows no corresponding precipitation reduction and temperature undergoes only a slight increase in the same period. On the other hand,evaporation is extremely high, higher than precipitation during most of the year, leaving alwaters of its tributaries are now occupied by a monoculture, Eucaliptus sp., used for paper production. Because of the decreased fluvial discharges, its lowlands, usually used for agriculture and pasture, are abandoned and partially eroded.