Revisiting the theory of interferometric wide-field synthesis

After several generations of interferometers in radioastronomy, wide-field imaging at high angular resolution is today a major goal for trying to match optical wide-field performances. All the radio-interferometric, wide-field imaging methods currently belong to the mosaicking family. Based on a 30 years old, original idea from Ekers & Rots, we aim at proposing an alternate formalism. Starting from their ideal case, we successively evaluate the impact of the standard ingredients of interferometric imaging. A comparison with standard nonlinear mosaicking shows that both processing schemes are not mathematically equivalent, though they both recover the sky brightness. In particular, the weighting scheme is very different in both methods. Moreover, the proposed scheme naturally processes the short spacings from both single-dish antennas and heterogeneous arrays. Finally, the sky gridding of the measured visibilities, required by the proposed scheme, may potentially save large amounts of hard-disk space and cpu processing power over mosaicking when handling data sets acquired with the on-the-fly observing mode. We propose to call this promising family of imaging methods wide-field synthesis because it explicitly synthesizes visibilities at a much finer spatial frequency resolution than the one set by the diameter of the interferometer antennas.Comment: 22 pages, 6 PostScript figures. Accepted for publication in Astronomy & Astrophysics. Uses aa LaTeX macros

Poder y contexto

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La mujer de Segovia

Copia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-201

The dangerous borders of the “community”: a challenge to the communications community

O texto reconhece a importância das associações comunitárias, principalmente as organizadas politicamente nesta época de globalização econômica e cultural, mas procura refletir sobre os usos do conceito de comunidade como instrumento de controle externo. O que encoraja os discursos que parecem querer manter os membros das comunidades atrás de muros físicos e conceituais? A discussão fundamental aqui é a possibilidade de auto-representação no momento em que a luta de diferentes grupos por visibilidade na mídia aumenta.The text recognizes the importance of community associations, especially those politically organized in this time of economic and cultural globalization, but seeks to reflect on the uses of the concept of community as an instrument of external control. What encourages the discourses that seem to want to keep the members of the communities behind (physical and conceptual) walls? The fundamental discussion here is about the possibility of self-representation when the struggle of different groups for visibility in the media increases

El puesto de Ramón Llull en la filosofía cristiana

Abstract not availabl

Lista comentada de la ictiofauna del Canal Beagle.

Inventario de la ictiofauna de la región, evaluación de aspectos de distribución y biología de las especies presentes. Además se incluyó la información completa de todas las entidades tratadas. Como resultado de este análisis se obtuvo un panorama actualizado del estado del conocimiento de los peces presentes en este sector. (PDF tiene 85 paginas.

Depositional style and tectonostratigraphic evolution of El Bierzo Tertiary sub-basin (Pyrenean orogen, NW Spain)

El Bierzo Tertiary sub-basin (Oligocene-Miocene, NW Spain) is a small remnant of the western Duero Basin, a nonmarine broken foreland basin developed in front of the Cantabrian Mountains (Pyrenean orogen). The alluvial infill of El Bierzo Tertiary sub-basin consists of a coarsening-upward succession from fluvial (Toral Formation) to alluvial-fan deposits (Las Médulas Formation) and reflects the uplift of the Cantabrian Mountains, in the north, and then of the related Galaico-Leoneses Mountains, in the south. These alluvial deposits show signs of having been laid down mainly by catastrophic flows (flood-dominated systems) and consist of three main depositional elements, namely, flood-plain fines, and lobe and channel conglomerates and sandstones. The vertical stacking patterns of these deposits and their relationships to the Alpine structures permit to unravel the tectonosedimentary evolution of the basin. The alluvial-plain element is the main constituent of a wide unconfined alluvial plain (Toral Formation) during the early stages of basin evolution, whereas the channel and lobe elements form a set of relatively small, laterally confined alluvial fans (Las Médulas Formation) fed first from the north and then from the south. Las Médulas deposits form two superposed units, the lower unit, cut by the Alpine thrusts, shows a progradational character, and the upper unit, which postdates most of the thrusts but not the youngest ones, displays a composite retrogradational trend. This organisation reflects the interplay between thrust emplacement and alluvial-fan sedimentation and suggests that maximum progradation took place during the climax of Alpine deformation