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1.
Accurate surface photometry has been obtained inJ andK for 12 giant elliptical galaxies. Ellipses have been fitted, to obtain luminosity, ellipticity, and major axis position angle profiles. The results have been combined with visual profiles from CCD observations. We find that elliptical galaxies become bluer inV - K on the average by 0.3 (mag/sq xr
e) going outward from the nucleus. Radial colour gradients inV - K correlate strongly with those inU - V andB - V. By modelling, using theoretical isochrones, it is found that the observed colour gradients can be explained by a gradient in metallicity, if in addition the proportion of hot stars rises very rapidly with decreasing metallicity. 相似文献
2.
Most workflow systems that support data provenance primarily focus on tracing lineage of data. Data provenance by data lineage provides the derivation history of data including information about services and input data that contributed to the creation of a data product. We show that tracing lineage by means of full backward chaining not only enables users to share, discover and reuse the data, but also supports scientific data processing through storage, retrieval and (re)processing of digitized scientific data. In this paper, we present Astro-WISE, a distributed system for processing, analyzing and disseminating wide field imaging astronomical data. We show how Astro-WISE traces lineage of data and how it facilitates data processing, retrieval, storage and archiving. Particularly we show how it solves issues related to the changing data items typical for the scientific environment, such as physical changes in calibrations, our insight in these changes and improved methods for deriving results. 相似文献
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Compared to the pre-launch measurements, the in-orbit noise levels ofthe Short Wavelength Spectrometer (SWS) detectors show a significantincrease, considerably lowering the overall sensitivity. Cosmic rayimpacts on the detectors and/or on the instrument electronics play animportant role in the noise levels and consequently many observations offaint sources are affected by this increased noise. However, by takingadvantage of the high read-out frequency of 24 Hz and the redundanciesprovided by the observing strategy, it is possible to significantlyimprove the quality of the data. Here, we present the concept ofself-calibration and additional algorithms, which are successfullyapplied to recover the weak signals of molecular hydrogen lines undetectable in a standard data reduction. 相似文献
4.
Hydrological model parameter estimation is an important aspect in hydrologic modelling. Usually, parameters are estimated through an objective function minimization, quantifying the mismatch between the model results and the observations. The objective function choice has a large impact on the sensitivity analysis and calibration outcomes. In this study, it is assessed whether spectral objective functions can compete with an objective function in the time domain for optimization of the Soil and Water Assessment Tool (SWAT). Three empirical spectral objective functions were applied, based on matching (i) Fourier amplitude spectra, (ii) periodograms and (iii) Fourier series of simulated and observed discharge time series. It is shown that most sensitive parameters and their optimal values are distinct for different objective functions. The best results were found through calibration with an objective function based on the square difference between the simulated and observed discharge Fourier series coefficients. The potential strengths and weaknesses of using a spectral objective function as compared to utilising a time domain objective function are discussed. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
5.
Syn‐sedimentary salt diapirism as a control on fluvial‐system evolution: an example from the proximal Permian Cutler Group,SE Utah,USA 
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下载免费PDF全文 Loading of subsurface salt during accumulation of fluvial strata can result in halokinesis and the growth of salt pillows, walls and diapirs. Such movement may eventually result in the formation of salt‐walled mini‐basins, whose style of architectural infill may be used to infer both the relative rates of salt‐wall growth and sedimentation and the nature of the fluvial‐system response to salt movement. The Salt Anticline Region of the Paradox Basin of SE Utah comprises a series of elongate salt‐walled mini‐basins, arranged in a NW‐trending array. The bulk of salt movement occurred during deposition of the Permian Cutler Group, a wedge of predominantly quartzo‐feldspathic clastic strata comprising sediment derived from the Uncompahgre Uplift to the NE. The sedimentary architecture of selected mini‐basin fills has been determined at high resolution through outcrop study. Mini‐basin centres are characterized by multi‐storey fluvial channel elements arranged into stacked channel complexes, with only limited preservation of overbank elements. At mini‐basin margins, thick successions of fluvial overbank and sheet‐like elements dominate in rim‐syncline depocentres adjacent to salt walls; many such accumulations are unconformably overlain by single‐storey fluvial channel elements that accumulated during episodes of salt‐wall breaching. The absence of gypsum clasts suggests that sediment influx was high, preventing syn‐sedimentary surface exposure of salt. Instead, fluvial breaching of salt‐generated topography reworked previously deposited sediments of the Cutler Group atop growing salt walls. Palaeocurrent data indicate that fluvial palaeoflow to the SW early in the history of basin infill was subsequently diverted to the W and ultimately to the NW as the salt walls grew to form topographic barriers. Late‐stage retreat of the Cutler fluvial system coincided with construction and accumulation of an aeolian system, recording a period of heightened climatic aridity. Aeolian sediments are preserved in the lees of some salt walls, demonstrating that halokinesis played a complex role in the differential trapping of sediment. 相似文献
6.
We present a novel approach to quality control during the processing of astronomical data. Quality control in the Astro-WISE Information System is integral to all aspects of data handing and provides transparent access to quality estimators for all stages of data reduction from the raw image to the final catalog. The implementation of quality control mechanisms relies on the core features in this Astro-WISE Environment (AWE): an object-oriented framework, full data lineage, and both forward and backward chaining. Quality control information can be accessed via the command-line awe-prompt and the web-based Quality-WISE service. The quality control system is described and qualified using archive data from the 8-CCD Wide Field Imager (WFI) instrument (http://www.eso.org/lasilla/instruments/wfi/) on the 2.2-m MPG/ESO telescope at La Silla and (pre-)survey data from the 32-CCD OmegaCAM instrument (http://www.astro-wise.org/~omegacam/) on the VST telescope at Paranal. 相似文献
7.
Jelte T. A. de Jong Gijs A. Verdoes Kleijn Konrad H. Kuijken Edwin A. Valentijn 《Experimental Astronomy》2013,35(1-2):25-44
The Kilo Degree Survey (KiDS) is a 1500 square degree optical imaging survey with the recently commissioned OmegaCAM wide-field imager on the VLT Survey Telescope (VST). A suite of data products will be delivered to the European Southern Observatory (ESO) and the community by the KiDS survey team. Spread over Europe, the KiDS team uses Astro-WISE as its main tool to collaborate efficiently and pool hardware resources. In Astro-WISE the team shares, calibrates and archives all survey data. The data-centric architectural design realizes a dynamic ‘live archive’ in which new KiDS survey products of improved quality can be shared with the team and eventually the full astronomical community in a flexible and controllable manner. 相似文献
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G. A. Verdoes Kleijn K. H. Kuijken E. A. Valentijn D. R. Boxhoorn K. G. Begeman E. R. Deul E. M. Helmich R. Rengelink 《Experimental Astronomy》2013,35(1-2):103-130
The OmegaCAM wide-field optical imager is the sole instrument on the VLT Survey Telescope at ESO’s Paranal Observatory. The instrument, as well as the telescope, have been designed for surveys with very good, natural seeing-limited image quality over a 1 square degree field. OmegaCAM was commissioned in 2011 and has been observing three ESO Public Surveys in parallel since October 15, 2011. We use the Astro-WISE information system to monitor the calibration of the observatory and to produce the Kilo Degree Survey (KiDS). Here we describe the photometric monitoring procedures in Astro-WISE and give a first impression of OmegaCAM’s photometric behavior as a function of time. The long-term monitoring of the observatory goes hand in hand with the KiDS survey production in Astro-WISE. KiDS is observed under partially non-photometric conditions. Based on the first year of OmegaCAM operations it is expected that a ～ 1–2 % photometric homogeneity will be achieved for KiDS. 相似文献
10.
John P. McFarland Gijs Verdoes-Kleijn Gert Sikkema Ewout M. Helmich Danny R. Boxhoorn Edwin A. Valentijn 《Experimental Astronomy》2013,35(1-2):45-78
We have designed and implemented a novel way to process wide-field astronomical data within a distributed environment of hardware resources and humanpower. The system is characterized by integration of archiving, calibration, and post-calibration analysis of data from raw, through intermediate, to final data products. It is a true integration thanks to complete linking of data lineage from the final catalogs back to the raw data. This paper describes the pipeline processing of optical wide-field astronomical data from the WFI (http://www.eso.org/lasilla/instruments/wfi/) and OmegaCAM (http://www.astro-wise.org/~omegacam/) instruments using the Astro-WISE information system (the Astro-WISE Environment or simply AWE). This information system is an environment of hardware resources and humanpower distributed over Europe. AWE is characterized by integration of archiving, data calibration, post-calibration analysis, and archiving of raw, intermediate, and final data products. The true integration enables a complete data processing cycle from the raw data up to the publication of science-ready catalogs. The advantages of this system for very large datasets are in the areas of: survey operations management, quality control, calibration analyses, and massive processing. 相似文献