Journal articles: 'Astronomie spatiale'

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Treps, Nicolas. "De l’imagerie quantique aux télécommunications : une histoire de modes." Photoniques, no. 92 (July 2018): 25–28. http://dx.doi.org/10.1051/photon/20189225.

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Du fait de ses potentielles applications, la mise en forme spatiale de la lumière est une des problématiques d’optique les plus actives. Ses succès sont déjà multiples, que ce soit en astronomie ou imagerie biologique, via l’optique adaptative, ou encore pour la focalisation à travers des milieux diffusants. L’optique quantique aussi y a puisé de l’inspiration, pour permettre en particulier d’ordonner spatialement les fluctuations quantiques et réaliser des expériences de métrologie quantique. De manière remarquable, les procédés développés pour ces études fondamentales ont des applications en télécommunications par fibre optique et ont permis de fonder la société CAILabs.

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Kaufmann, P., E. Correia, J. E. R. Costa, and A. M. Zodi. "Far Infrared and Submillimeter Continuum Observations of Solar Flares: Justifications and Prospects for Ground-Based Experiments." Symposium - International Astronomical Union 154 (1994): 93–101. http://dx.doi.org/10.1017/s0074180900124313.

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Solar flare observations in the sub-mm spectral bands are essentially non-existent. There is evidence that some solar bursts exhibit a spectral component rising in intensity towards wavelengths shorter than 3 mm, displaying fast sub-second pulses at different repetition rates. On the other hand, the spectral features of white light flares are also unknown in the infra-red range of frequencies. In both wavelength ranges the physics of the emission processes may involve particles accelerated to high energies. The diagnostics of solar flare continuum emission in the IR and sub-mm spectral regions will provide crucial tests on various flare models and bring some clues on the initial primary energy release mechanisms. We propose the construction and operation of a ground-based telescope, operating at two sub-millimeter wavelengths (at about 210 GHz and 405 GHz), with high time resolution (one millisecond), capable of determining the spatial position of burst emission centroids with high definition (a few arcseconds) using the multiple beam technique. Final installation and operation at a high-altitude site in the Argentinian Andes mountains are planned in a joint cooperation with Argentina's Instituto de Astronomia y Fisica del Espacio, IAFE (M. Rovira and associates) and Complejo Astronomico El Leoncito, CASLEO, San Juan (H. Levato and associates); and Switzerland's University of Bern, Institute of Applied Physics, IAP, Bern (A. Magun and associates).

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Babu, Gutti Jogesh, and Eric D. Feigelson. "Spatial point processes in astronomy." Journal of Statistical Planning and Inference 50, no. 3 (March 1996): 311–26. http://dx.doi.org/10.1016/0378-3758(95)00060-7.

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Lacombe, Mireille. "La vulgarisation scientifique au Planétarium de Montréal." Scientia Canadensis 38, no. 2 (November 14, 2016): 21–33. http://dx.doi.org/10.7202/1037944ar.

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Cet article retrace l’histoire du Planétarium Dow de Montréal, en mettant l’accent sur la vulgarisation scientifique qui s’y pratique. À son ouverture en 1966, les activités visent d’abord un public adulte et portent surtout sur la conquête spatiale. Le planétarium travaille alors conjointement avec les astronomes amateurs et participe à la fondation de l’Association des planétariums canadiens. Après 1971, le planétarium se tourne graduellement vers les publics scolaires et diversifie ses spectacles. Dans les années 1980, les thèmes des spectacles changent, alors que le planétarium engage des astronomes diplômés. Dans les années 1990, la création du regroupement des Muséums Nature Montréal joue un rôle crucial dans le développement de l’institution, notamment avec la création de la Société des astronomes amateurs du Planétarium de Montréal et la promotion du loisir scientifique destiné aux jeunes. Au tournant du siècle, faisant face à des équipements désuets, le planétarium mise sur la diversification de ses types d’activités et offre de plus en plus d’activités hors de ses murs.

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Bucur, Doina. "The network signature of constellation line figures." PLOS ONE 17, no. 7 (July 28, 2022): e0272270. http://dx.doi.org/10.1371/journal.pone.0272270.

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In traditional astronomies across the world, groups of stars in the night sky were linked into constellations—symbolic representations rich in meaning and with practical roles. In some sky cultures, constellations are represented as line (or connect-the-dot) figures, which are spatial networks drawn over the fixed background of stars. We analyse 1802 line figures from 56 sky cultures spanning all continents, in terms of their network, spatial, and brightness features, and ask what associations exist between these visual features and culture type or sky region. First, an embedded map of constellations is learnt, to show clusters of line figures. We then form the network of constellations (as linked by their similarity), to study how similar cultures are by computing their assortativity (or homophily) over the network. Finally, we measure the diversity (or entropy) index for the set of constellations drawn per sky region. Our results show distinct types of line figures, and that many folk astronomies with oral traditions have widespread similarities in constellation design, which do not align with cultural ancestry. In a minority of sky regions, certain line designs appear universal, but this is not the norm: in the majority of sky regions, the line geometries are diverse.

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Heyer, Inge, Stephanie J. Slater, and Timothy F. Slater. "ESTABLISHING THE EMPIRICAL RELATIONSHIP BETWEEN NON-SCIENCE MAJORING UNDERGRADUATE LEARNERS’ SPATIAL THINKING SKILLS AND THEIR CONCEPTUAL ASTRONOMY KNOWLEDGE." Revista Latino-Americana de Educação em Astronomia, no. 16 (December 1, 2013): 45–61. http://dx.doi.org/10.37156/relea/2013.16.045.

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A comunidade da educação em astronomia tem suposto de forma implícita que o aprendizado da astronomia consiste em um domínio conceitual fundamentado no raciocínio espacial. Como um primeiro passo para identificar formalmente uma relação empírica entre estas duas coisas, utilizamos como amostra os estudantes de graduação de carreiras não científicas de um curso exploratório em uma universidade norte-americana do meio-oeste de médio porte com programa de Doutorado em andamento, onde estes estudantes foram submetidos a um diagnóstico de raciocino espacial e conceitos astronômicos antes e depois do mesmo. As ferramentas utilizadas foram o Test Of Astronomy Standards (TOAST) e o questionário What do you know? Utilizando somente dados completamente consistentes para esta análise, nossa amostra consistiu de 86 estudantes de graduação. As melhoras, depois de normalizadas, do desempenho dos estudantes nos dois quesitos foram pequenas, 0.26 e 0.13 respectivamente. O raciocínio espacial dos estudantes foi medido utilizando um instrumento específico desenhado para este trabalho. As correlações entre os resultados dos testes astronômicos e este instrumento específico antes e depois do curso mostraram uma relação entre moderada e forte, sugerindo que a relação entre o raciocínio espacial e o conhecimento astronômico pode explicar até um 25% na variação no desempenho dos estudantes.

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TURK, Cumhur. "The Correlation between Pre-Service Science Teachers’ Astronomy Achievement, Attitudes towards Astronomy and Spatial Thinking Skills." Journal of Education and Learning 5, no. 2 (March 22, 2016): 187. http://dx.doi.org/10.5539/jel.v5n2p187.

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<p>The purpose of this study was to examine the changes in pre-service Science teachers’ astronomy achievement, attitudes towards astronomy and skills for spatial thinking in terms of their years of study. Another purpose of the study was to find out whether there was correlation between pre-service teachers’ astronomy achievement, attitudes towards astronomy and skills for spatial thinking. The study was conducted with 280 pre-service teachers (freshmen, sophomores, juniors and seniors) studying at the education faculty of a university in Black Sea Region of Turkey. The data were collected through Astronomy Achievement Test, Astronomy Attitude Test and Purdue Spatial Visualization Test: Visualization of Rotations. One way factor analysis (One-Way Anova) technique for independent groups was used for data analysis in order to find out whether pre-service teachers’ astronomy achievement, attitudes towards astronomy and skills for spatial thinking differed in terms of their years of study. In order to find out whether there was correlation between pre-service teachers’ astronomy achievement, attitudes towards astronomy and skills for spatial thinking, simple linear correlation analysis was conducted and Pearson Moment Correlation Coefficient was checked. The results of the data analysis showed that pre-service teachers’ astronomy achievement, attitudes towards astronomy and skills for spatial thinking differed significantly in terms of their years of study. In addition, a low positive correlation was found between pre-service teachers’ astronomy achievement and attitudes towards astronomy while a high positive correlation was found between pre-service teachers’ astronomy achievement and their skills for spatial thinking. In line with these results, recommendations were made to increase the number of astronomy classes in education faculties and to teach astronomy not only in fourth year but also in the first three years.</p>

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Raza, J., A. J. Boonstra, and A. J. van der Veen. "Spatial filtering of RF interference in radio astronomy." IEEE Signal Processing Letters 9, no. 2 (February 2002): 64–67. http://dx.doi.org/10.1109/97.991140.

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Wamsteker, Willem, S. Baliunas, N. Brosch, C. Cesarsky, Th J. L. Courvoisier, J. M. da Costa, V. Domingo, et al. "Division XI: Space and High Energy Astrophysics(Astrophysique Spatiale et Des Hautes Energies)." Transactions of the International Astronomical Union 24, no. 1 (2000): 357–67. http://dx.doi.org/10.1017/s0251107x0000331x.

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The reporting period has shown that Space has become a firmly established domain in observational Astrophysics, also in the low energy astrophysics area. The launching of new spacecraft is always an important addition to the capabilities of the Astronomers, but the availability of space observatories is strongly affected by the fact that they disappear as their subsystems become damaged or, for other reasons, become inoperable. The relatively short life of astronomical space facilities has generated new dynamic in the life cycle of observational tools for the astronomer, rather different from that for ground facilities. Launch failures or the final in-orbit functionality verification can also very strongly affect the availability of observational capabilities in space astrophysics. The only spacecraft designed without this built-in life time restriction, is the Hubble Space Telescope, which can be serviced by the Space Shuttle.

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Hellbourg, Grégory, Rodolphe Weber, Cécile Capdessus, and Albert-Jan Boonstra. "Cyclostationary approaches for spatial RFI mitigation in radio astronomy." Comptes Rendus Physique 13, no. 1 (January 2012): 71–79. http://dx.doi.org/10.1016/j.crhy.2011.10.010.

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Carbonel, Cyril, Sébastien Grasset, and Jean Maysonnave. "Accessing High Spatial Resolution in Astronomy Using Interference Methods." Physics Teacher 56, no. 4 (April 2018): 232–34. http://dx.doi.org/10.1119/1.5028239.

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Picquenot, A., F. Acero, J. Bobin, P. Maggi, J. Ballet, and G. W. Pratt. "Novel method for component separation of extended sources in X-ray astronomy." Astronomy & Astrophysics 627 (July 2019): A139. http://dx.doi.org/10.1051/0004-6361/201834933.

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In high-energy astronomy, spectro-imaging instruments such as X-ray detectors allow investigation of the spatial and spectral properties of extended sources including galaxy clusters, galaxies, diffuse interstellar medium, supernova remnants, and pulsar wind nebulae. In these sources, each physical component possesses a different spatial and spectral signature, but the components are entangled. Extracting the intrinsic spatial and spectral information of the individual components from this data is a challenging task. Current analysis methods do not fully exploit the 2D-1D (x, y, E) nature of the data, as spatial information is considered separately from spectral information. Here we investigate the application of a blind source separation (BSS) algorithm that jointly exploits the spectral and spatial signatures of each component in order to disentangle them. We explore the capabilities of a new BSS method (the general morphological component analysis; GMCA), initially developed to extract an image of the cosmic microwave background from Planck data, in an X-ray context. The performance of the GMCA on X-ray data is tested using Monte-Carlo simulations of supernova remnant toy models designed to represent typical science cases. We find that the GMCA is able to separate highly entangled components in X-ray data even in high-contrast scenarios, and can extract the spectrum and map of each physical component with high accuracy. A modification of the algorithm is proposed in order to improve the spectral fidelity in the case of strongly overlapping spatial components, and we investigate a resampling method to derive realistic uncertainties associated to the results of the algorithm. Applying the modified algorithm to the deep Chandra observations of Cassiopeia A, we are able to produce detailed maps of the synchrotron emission at low energies (0.6–2.2 keV), and of the red- and blueshifted distributions of a number of elements including Si and Fe K.

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OKADA, Daiji, and Takuya MATSUURA. "A Comparative Study on the Spatial Cognition of Students in Astronomy." Journal of Graphic Science of Japan 48, no. 2-3 (2014): 3–10. http://dx.doi.org/10.5989/jsgs.48.2-3_3.

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van, S., and A. J. van der Veen. "Performance analysis of spatial filtering of RF interference in radio astronomy." IEEE Transactions on Signal Processing 53, no. 3 (March 2005): 896–910. http://dx.doi.org/10.1109/tsp.2004.842177.

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Brady, Bernadette. "Stars and Cultural Astronomy." Journal of Skyscape Archaeology 4, no. 1 (August 3, 2018): 129–33. http://dx.doi.org/10.1558/jsa.36095.

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Stars are ubiquitous; the Sun and Moon are singletons. The Sun and the Moon visually dominate the sky. They change in the amount of light they produce, either monthly or yearly. They also rhythmically change how they embrace the horizon, creating a measure of time and seasons. In contrast, the stars are many and their light is small. Their place in the sky is fixed and, ignoring precession, their relationship to the horizon is constant, always rising or setting at the same point. They are different in almost every way to the luminaries, in their multiplicity, light, fixed spatial relationship to each other and fixity in a landscape. These distinct characteristics mean that the stars are a catalyst for sky narratives quite different from those of the luminaries. The most easily recognisable stellar sky narratives are the constellation stories. The multiplicity of the stars produces a scattering of lights across the night sky according to a fixed pattern which, to the human mind - with its apophenia, the tendency to see patterns - results in the heavens becoming a vast storyboard of constellations and clusters. These stories are placed on bright stars, dim stars, coloured stars, dark gaps or voids, and milky hazes. Every spot of the dome of the heavens holds some culture's myth, some culture's cosmic narrative, and every visible place in the dome of the heavens has been claimed by most cultures. Their consistency of movement and fixedness in orientation to each other, however, also offer humanity something quite unique: a view of eternity.

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Jessner, A. "Industrial interference and radio astronomy." Advances in Radio Science 11 (July 4, 2013): 251–58. http://dx.doi.org/10.5194/ars-11-251-2013.

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Abstract. The interferer – victim scenario is described for the case of industrial interference affecting radio astronomical observatories. The sensitivity of radio astronomical receivers and their interference limits are outlined. EMC above 30 MHz is a serious problem for Radio Astronomy. Interferer (CISPR) and victim (ITU-R RA 769) standards are not harmonised. The emissions from the interferer and their spectral characteristics are not defined sufficiently well by CISPR standards. The required minimum coupling losses (MCL) between an industrial device and radio astronomical antenna depends on device properties but is shown to exceed 140 dB in most cases. Spatial separation of a few km is insufficient on its own, the terrain must shield > 30–40 dB, additional mitigations such as extra shielding or suppression of high frequency emissions may be necessary. A case by case compatibility analysis and tailored EMC measures are required for individual installations. Aggregation of many weak rfi emitters can become serious problem. If deployment densities are high enough, the emission constraints can even exceed those for a single interferer at a short distance from the radio observatory. Compatibility studies must account not only for the single interferer but also for many widely distributed interference sources.

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Isham, V., D. R. Cox, I. Rodríguez-Iturbe, A. Porporato, and S. Manfreda. "Representation of space–time variability of soil moisture." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 461, no. 2064 (October 10, 2005): 4035–55. http://dx.doi.org/10.1098/rspa.2005.1568.

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A simplified spatial-temporal soil moisture model driven by stochastic spatial rainfall forcing is proposed. The model is mathematically tractable, and allows the spatial and temporal structure of soil moisture fields, induced by the spatial-temporal variability of rainfall and the spatial variability of vegetation, to be explored analytically. The influence of the main model parameters, reflecting the spatial scale of rain cells, the soil storage capacity, the rainfall interception and the soil water loss rate (representing evaporation and deep infiltration) is investigated. The variabilities of the spatially averaged soil moisture process, and that averaged in both space and time, are derived. The present analysis focuses on spatially uniform vegetation conditions; a follow-up paper will incorporate stochastically heterogeneous vegetation.

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Taylor, B. G., and A. Peacock. "ESA’s X-Ray Astronomy Mission, XMM." International Astronomical Union Colloquium 123 (1990): 129–40. http://dx.doi.org/10.1017/s0252921100076971.

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AbstractESA’s X-ray Astronomy Mission, XMM, scheduled for launch in 1998, is the second of four cornerstones of ESA’s long term science program Horizon 2000. Covering the range from about 0.1 to 10 keV, it will provide a high throughput of 5000 cm2 at 7 keV with three independant telescopes, and have a spatial resolution better than 30 arcsec. Broadband spectrophotometry is provided by CCD cameras while reflection gratings provide medium resolution spectroscopy (resolving power of about 400) in the range 0.3–3 keV. Long uninterrupted observations will be made from the 24 hr period, highly eccentric orbit, reaching a sensitivity approaching 10−15 erg cm−2 s−1 in one orbit. A 30 cm UV/optical telescope is bore-sighted with the x-ray telescopes to provide simultaneous optical counterparts to the numerous serendipitous X-ray sources which will be detected during every observation.

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Jin-Ping, Li, Lu Ke-Qing, Zhao Wei, Yang Yan-Long, Zhu Xiang-Ping, and Guo Xiao-Hui. "Two-Dimensional Photovoltaic Dark Spatial Solitons of Partially Spatially Incoherent Light." Chinese Physics Letters 22, no. 6 (May 25, 2005): 1423–25. http://dx.doi.org/10.1088/0256-307x/22/6/034.

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Chuang, Li, Leng Yu-Xin, Zhang Chun-Mei, Liang Xiao-Yan, Li Ru-Xin, and Xu Zhi-Zhan. "An Ultra-Broadband Spatially Dispersed Regenerative Amplifier Free from Spatial Chirp." Chinese Physics Letters 25, no. 6 (May 29, 2008): 2048–50. http://dx.doi.org/10.1088/0256-307x/25/6/034.

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Dao, M. H., and P. Tkalich. "Tsunami propagation modelling – a sensitivity study." Natural Hazards and Earth System Sciences 7, no. 6 (December 3, 2007): 741–54. http://dx.doi.org/10.5194/nhess-7-741-2007.

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Abstract. Indian Ocean (2004) Tsunami and following tragic consequences demonstrated lack of relevant experience and preparedness among involved coastal nations. After the event, scientific and forecasting circles of affected countries have started a capacity building to tackle similar problems in the future. Different approaches have been used for tsunami propagation, such as Boussinesq and Nonlinear Shallow Water Equations (NSWE). These approximations were obtained assuming different relevant importance of nonlinear, dispersion and spatial gradient variation phenomena and terms. The paper describes further development of original TUNAMI-N2 model to take into account additional phenomena: astronomic tide, sea bottom friction, dispersion, Coriolis force, and spherical curvature. The code is modified to be suitable for operational forecasting, and the resulting version (TUNAMI-N2-NUS) is verified using test cases, results of other models, and real case scenarios. Using the 2004 Tsunami event as one of the scenarios, the paper examines sensitivity of numerical solutions to variation of different phenomena and parameters, and the results are analyzed and ranked accordingly.

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Dubau, Jacques. "Atomic Data Needed for Solar Astronomy from Space." Highlights of Astronomy 9 (1992): 569–70. http://dx.doi.org/10.1017/s1539299600009771.

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The UV and X-ray wavelength ranges are rich in emission unes from the transition region and the corona, formed at temperatures from 104 K to 107 K. Fortunately, these emission lines, absorbed by the earth upper atmosphere, can be observed by some solar space observatories. In particular, the NASA SMM satellite, from 1980 to 1990, has obtained very interesting spectra from which important solar results were derived. In a close future, they will be again observed but with improved spectral, spatial and temporal resolution by SOLAR-A and SOHO.

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Viñas, Maria. "From Astronomy to the clinic: Adaptive Optics based visual simulators." Europhysics News 51, no. 3 (May 2020): 17–19. http://dx.doi.org/10.1051/epn/2020302.

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Adaptive optics based visual simulators with deformable mirrors, spatial light modulators or optotunable lenses are increasingly used to simulate vision through different complex multifocal lens designs. Their final utility in the clinic relies on their capability to predict visual performance after an ocular surgery.

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Aksaker, N., S. K. Yerli, M. A. Erdoğan, Z. Kurt, K. Kaba, M. Bayazit, and C. Yesilyaprak. "Global Site Selection for Astronomy." Monthly Notices of the Royal Astronomical Society 493, no. 1 (February 25, 2020): 1204–16. http://dx.doi.org/10.1093/mnras/staa201.

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ABSTRACT A global site selection for astronomy was performed with 1 km spatial resolution (∼1 gigapixel in size) using long-term and up-to-date datasets to classify the entire terrestrial surface of the Earth. Satellite instruments are used to get the following datasets of geographical information system (GIS) layers: cloud coverage, digital elevation model, artificial light, precipitable water vapour, aerosol optical depth, wind speed, and land use and land cover. A multi-criteria decision analysis (MCDA) technique is applied to these datasets, creating four different series where each layer will have a specific weight. We introduce for the first time a suitability index for astronomical sites (SIAS). This index can be used to find suitable locations and to compare different sites or observatories. The midwestern Andes in South America and the Tibetan Plateau in western China were found to be the best in all SIAS series. Considering all the series, less than 3 per cent of all terrestrial surfaces are found to be the best regions to establish an astronomical observatory. In addition to this, only approximately 10 per cent of all current observatories are located in good locations in all SIAS series. Amateurs, institutions or countries aiming to construct an observatory could create a shortlist of potential site locations using a layout of SIAS values for each country without spending time and budget. The outcomes and datasets of this study have been made available through a website, the Astro GIS Database, at www.astrogis.org.

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Taylor, Roger S., and Erika D. Grundstrom. "Diagrammatic Representational Constraints of Spatial Scale in Earth–Moon System Astronomy Instruction." Astronomy Education Review 10, no. 1 (December 2011): 010104–010104. http://dx.doi.org/10.3847/aer2009075.

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Hill, Lon Clay. "Spatial Thinking and Learning Astronomy: The Implicit Visual Grammar of Astronomical Paradigms." International Astronomical Union Colloquium 105 (1990): 247–48. http://dx.doi.org/10.1017/s0252921100086875.

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As several previous speakers have noted, astronomers are a rare breed. Even though we represent the oldest science, we are as rare as poets. The fact that our discipline is so distinct suggests that it should also have its peculiar pedagogical problems. I have been attempting to understand a pervasive element of all astronomical thinking — the use of spatial imagination to link celestial phenomena to terrestrial analogs. My work has two components — a theoretical explication of astronomical thinking and some practical use of these ideas in teaching situations.If one looks at some of the fundamental “facts” discovered by astronomers, we will find that we often do not, in fact, directly verify our discoveries as scientists supposedly do. Primary astronomical “truths” such as the sphericity of the Earth, the heliocentric orbit of the Earth, the identification of the stars as distant suns, and the recognition that galaxies are enormous collections of stars, were not discovered by direct verification. Thus, we note that the Greeks discovered the Earth’s sphericity nearly two millennia before its circumnavigation and that only a few thousand very bright stars in nearby galaxies have been resolved in our largest telescopes. Some of the primary objects of astronomical discourse, then, are not perceptible objects, but objects created by the spatial imagination.

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Plummer, Julia D. "Spatial thinking as the dimension of progress in an astronomy learning progression." Studies in Science Education 50, no. 1 (January 2, 2014): 1–45. http://dx.doi.org/10.1080/03057267.2013.869039.

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Piccolini, Matteo, Farzam Nosrati, Giuseppe Compagno, Patrizia Livreri, Roberto Morandotti, and Rosario Lo Franco. "Entanglement Robustness via Spatial Deformation of Identical Particle Wave Functions." Entropy 23, no. 6 (June 3, 2021): 708. http://dx.doi.org/10.3390/e23060708.

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We address the problem of entanglement protection against surrounding noise by a procedure suitably exploiting spatial indistinguishability of identical subsystems. To this purpose, we take two initially separated and entangled identical qubits interacting with two independent noisy environments. Three typical models of environments are considered: amplitude damping channel, phase damping channel and depolarizing channel. After the interaction, we deform the wave functions of the two qubits to make them spatially overlap before performing spatially localized operations and classical communication (sLOCC) and eventually computing the entanglement of the resulting state. This way, we show that spatial indistinguishability of identical qubits can be utilized within the sLOCC operational framework to partially recover the quantum correlations spoiled by the environment. A general behavior emerges: the higher the spatial indistinguishability achieved via deformation, the larger the amount of recovered entanglement.

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Jeong, Il-Gyo, and Bon-Chul Koo. "SRAO CO Observation of Supernova Remnants in l = 70° to 190°." Proceedings of the International Astronomical Union 9, S296 (January 2013): 183–87. http://dx.doi.org/10.1017/s1743921313009447.

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AbstractWe present the results 12CO J = 1–0 line observations of eleven Galactic supernova remnants (SNRs) between l = 70° and 190° obtained using the Seoul Radio Astronomy Observatory (SRAO) 6-m radio telescope. We detected CO emission towards most of the remnants. In seven SNRs, molecular clouds show a good spatial relation with their radio morphology: G73.9+0.9, G84.2−0.8, G85.4+0.7, G85.9−0.6, G93.3+6.9 (DA530), 94.0+1.0 (3C 434.1), and G182.4+4.3. Two SNRs are particularly interesting. In G85.4+0.7, there is a filamentary molecular cloud aligned along the south-east boundary of the remnant. This cloud extends to the nearby Hii region G84.9+0.5. If the molecular cloud is associated with both the Hii region and the SNR, the distance to the SNR would be 5–7 kpc. In 3C 434.1, there is a large molecular cloud blocking the western half of the remnant where the radio continuum emission is faint. The cloud shows a very good spatial correlation with radio continuum features, which strongly suggests the physical association of the cloud with the SNR. This gives a distance of 3 kpc to the SNR. We performed 12CO J = 2–1 line observations of this cloud using Kölner Observatorium für Sub-Millimeter Astronomie (KOSMA) 3-m telescope and found a region where the 12CO J = 2–1/1–0 line ratio is high. We present a hydrodynamic model showing that 3C434.1 could have resulted from a SN explosion occurred just outside the boundary of a thin, molecular cloud.

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Martinez-Castellanos, I., Leo P. Singer, E. Burns, D. Tak, Alyson Joens, Judith L. Racusin, and Jeremy S. Perkins. "Multiresolution HEALPix Maps for Multiwavelength and Multimessenger Astronomy." Astronomical Journal 163, no. 6 (May 11, 2022): 259. http://dx.doi.org/10.3847/1538-3881/ac6260.

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Abstract HEALPix—the Hierarchical Equal Area isoLatitude Pixelization—has become a standard in high-energy and gravitational wave astronomy. Originally developed to improve the efficiency of all-sky Fourier analyses, it is now also utilized to share sky localization information. When used for this purpose the need for a homogeneous all-sky grid represents a limitation that hinders a broader community adoption. This work presents mhealpy, a Python library able to create, handle and analyze multiresolution maps, a solution to this problem. It supports efficient pixel querying, arithmetic operations between maps, adaptive mesh refinement, plotting, and serialization into FITS—Flexible Image Transport System—files. This HEALPix extension makes it suitable to represent highly resolved region, resulting in a convenient common format to share spatial information for joint multiwavelength and multimessenger analyses.

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Blecha, A. "CCDs in Active Acquisition Systems." Symposium - International Astronomical Union 167 (1995): 57–66. http://dx.doi.org/10.1017/s0074180900056266.

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The use of CCD detectors as elements of an active acquisition system is reviewed. In such systems, the CCD image acquisition, data-analysis and the instrument and telescope controls are no longer separated elements whose actions are coordinated by an astronomer and/or operator, but are parts of a global system. The interaction between incoming data (nature of the object, registered flux, current PSF and atmospheric transmission), observer's requirement (S/N, spatial and temporal resolution) and forthcoming CCD exposure characteristics (CCD preparation, exposure time, read-out parameters) is examined. The requirements for the CCD electronics, data acquisition system are evaluated and examples of recent application in imaging, spectroscopy, photometry and auxiliary equipment are given. An attempt is made to analyze future technological trends and possible bottlenecks in such systems and to propose simple rules to adopt when designing CCD hardware and software.

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Penchèvre, Erwan. "VÉNUS SELON IBN AL-ŠĀṬIR." Arabic Sciences and Philosophy 26, no. 2 (August 5, 2016): 185–214. http://dx.doi.org/10.1017/s0957423916000011.

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AbstractWe attempt to grasp the mathematics behind the planetary theories of the Syrian astronomer Ibn al-Šāṭir (1304–1375) in his treatise Nihāyat al-Sūl. Following the astronomers of the Marāgha school, by composing circular movements with constant angular velocity, Ibn al-Šāṭir attains two goals. He eliminates the need of excentrics and equant points in astronomy; but he also describes longitudes and latitudes with a unique method, with no more orbs than what is strictly necessary for the longitudes. A better understanding of rotation as a spatial transformation enables this ultimate economy of thought. In our commentary, we take Venus as an example offering an interesting problem about the latitudes. This is an opportunity to give a critical edition of the chapter of the Nihāyat al-Sūl dedicated to the latitudes of Mercury and Venus.

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Yin-Xia, Han, Li Jing-Hui, Zhao Ying-Kui, and Chen Shi-Gang. "Spatially Periodic System with Infinite Globally Coupled Oscillators Driven by Temporal-Spatial Noise." Communications in Theoretical Physics 43, no. 1 (January 2005): 92–96. http://dx.doi.org/10.1088/0253-6102/43/1/019.

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Lelliott, Anthony. "The concept of spatial scale in astronomy addressed by an informal learning environment." African Journal of Research in Mathematics, Science and Technology Education 14, no. 3 (January 2010): 20–33. http://dx.doi.org/10.1080/10288457.2010.10740689.

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Sardarabadi, Ahmad Mouri, Alle-Jan van der Veen, and Albert-Jan Boonstra. "Spatial Filtering of RF Interference in Radio Astronomy Using a Reference Antenna Array." IEEE Transactions on Signal Processing 64, no. 2 (January 2016): 432–47. http://dx.doi.org/10.1109/tsp.2015.2483481.

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Cheema, Amna Umer. "Bishop, Kepler and Sarduy: Ellipse and Ellipsis." Bishop–Lowell Studies 2 (July 1, 2022): 70–112. http://dx.doi.org/10.5325/bishoplowellstud.2.0070.

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Abstract This article expands on Elizabeth Bishop’s affinity with the Cuban poet and critic Severo Sarduy and his neo-baroque reading of the seventeenth-century mathematician and astronomer Johannes Kepler’s planetary geometry of the imperfect circle called the ellipse and its linguistic equivalent the ellipsis (Sarduy 293). This essay will elucidate the geometrical decentering of space and the linguistic decentering of meanings as characteristics of ellipse and ellipsis through a discussion of Bishop’s poems, “In the Waiting Room,” “The Bight” and “One Art.” I argue that Bishop’s engagement with ellips(e/is) is a spatial response to the destabilization of modern urban space and the gap between language and signification, akin to T.S. Eliot’s ideas about the gap between thought and feeling in modern sensibility. Through ellips(e/is), Bishop seeks a perspective outside definitive contours and finds beauty in an incomplete and distorted embodiment of an ever-becoming truth.

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Liu Dong-Bing, Cheng Jin-Ming, Qi Shuang-Xi, Wang Wan-Li, and Qian Wei-Xin. "Spatial correlation properties of focused spatially and spectrally partially coherent Hemite-Gaussian pulsed beams." Acta Physica Sinica 61, no. 24 (2012): 244202. http://dx.doi.org/10.7498/aps.61.244202.

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Ding, Yumei, and Lei Ding. "A Numerical Simulation of Extratropical Storm Surge and Hydrodynamic Response in the Bohai Sea." Discrete Dynamics in Nature and Society 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/282085.

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A hindcast of typical extratropical storm surge occurring in the Bohai Sea in October 2003 is performed using a three-dimensional (3D) Finite Volume Coastal Ocean Model (FVCOM). The storm surge model is forced by 10 m winds obtained from the Weather Research Forecasting (WRF) model simulation. It is shown that the simulated storm surge and tides agree well with the observations. The nonlinear interaction between the surge and astronomical tides, the spatial distribution of the maximum surge level, and the hydrodynamic response to the storm surge are studied. The storm surge is the interaction of the surge and the astronomical tides. The currents change rapidly during the storm surge and turn to be the unidirectional at some places where the tidal currents are usually rectilinear. The results show that the local surge current velocity in each depth, with a magnitude of the same order as the astronomic tidal currents, increases or decreases rapidly depending on the relationship between the winds and current directions. Furthermore, the current pattern gets more complicated under the influence of the direction of the winds, which might affect sand movement in the coastal water of the Bohai Sea.

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Cunden, Fabio Deelan, Sara Di Martino, Paolo Facchi, and Giuseppe Florio. "Spatial separation and entanglement of identical particles." International Journal of Quantum Information 12, no. 02 (March 2014): 1461001. http://dx.doi.org/10.1142/s0219749914610012.

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We reconsider the effect of indistinguishability on the reduced density operator of the internal degrees of freedom (tracing out the spatial degrees of freedom) for a quantum system composed of identical particles located in different spatial regions. We explicitly show that if the spin measurements are performed in disjoint spatial regions then there are no constraints on the structure of the reduced state of the system. This implies that the statistics of identical particles has no role from the point of view of separability and entanglement when the measurements are spatially separated. We extend the treatment to the case of n particles and show the connection with some recent criteria for separability based on subalgebras of observables.

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Gorenstein, Paul. "Focusing X-Ray Optics for Astronomy." X-Ray Optics and Instrumentation 2010 (December 27, 2010): 1–19. http://dx.doi.org/10.1155/2010/109740.

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Focusing X-ray telescopes have been the most important factor in X-ray astronomy’s ascent to equality with optical and radio astronomy. They are the prime tool for studying thermal emission from very high temperature regions, non-thermal synchrotron radiation from very high energy particles in magnetic fields and inverse Compton scattering of lower energy photons into the X-ray band. Four missions with focusing grazing incidence X-ray telescopes based upon the Wolter 1 geometry are currently operating in space within the 0.2 to 10 keV band. Two observatory class missions have been operating since 1999 with both imaging capability and high resolution dispersive spectrometers. They are NASA’s Chandra X-ray Observatory, which has an angular resolution of 0.5 arc seconds and an area of 0.1 m2 and ESA’s XMM-Newton which has 3 co-aligned telescopes with a combined effective area of 0.43 m2 and a resolution of 15 arc seconds. The two others are Japan’s Suzaku with lower spatial resolution and non-dispersive spectroscopy and the XRT of Swift which observes and precisely positions the X-ray afterglows of gamma-ray bursts. New missions include focusing telescopes with much broader bandwidth and telescopes that will perform a new sky survey. NASA, ESA, and Japan’s space agency are collaborating in developing an observatory with very large effective area for very high energy resolution dispersive and non-dispersive spectroscopy. New technologies are required to improve upon the angular resolution of Chandra. Adaptive optics should provide modest improvement. However, orders of magnitude improvement can be achieved only by employing physical optics. Transmitting diffractive-refractive lenses are capable theoretically of achieving sub-milli arc second resolution. X-ray interferometry could in theory achieve 0.1 micro arc second resolution, which is sufficient to image the event horizon of super massive black holes at the center of nearby active galaxies. However, the physical optics systems have focal lengths in the range 103 to 104 km and cannot be realized until the technology for accurately positioned long distance formation flying between optics and detector is developed.

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Ortolano, Giuseppe, Ivano Ruo-Berchera, and Enrico Predazzi. "Quantum enhanced imaging of nonuniform refractive profiles." International Journal of Quantum Information 17, no. 08 (December 2019): 1941010. http://dx.doi.org/10.1142/s0219749919410107.

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In this work, quantum metrology techniques are applied to the imaging of objects with a nonuniform refractive spatial profile. A sensible improvement on the classical accuracy is shown to be found when the “Twin Beam (TWB) State” is used. In particular, exploiting the multimode spatial correlation, naturally produced in the Parametric Down Conversion (PDC) process, allows a 2D reconstruction of complex spatial profiles, thus enabling an enhanced imaging. The idea is to use one of the spatially multimode beams to probe the sample and the other as a reference to reduce the noise. A similar model can also be used to describe wave front distortion measurements. The model is meant to be followed by a first experimental demonstration of such enhanced measurement scheme.

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Guibaly, Fayez El. "Models for the bulk photovoltaic effect in ferroelectric crystals." Canadian Journal of Physics 66, no. 8 (August 1, 1988): 649–54. http://dx.doi.org/10.1139/p88-108.

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Three models for the bulk photovoltaic effect in electrooptic crystals are discussed. All models produce the same results. First, the photocurrent responsible for hologram storage is spatially shifted relative to the optical pattern that produced it. Second, the efficiency of hologram recording decreases with increases in the spatial frequency of the optical interference pattern. Third, the efficiency of hologram recording decreases for crystals exhibiting a strong bulk photovoltaic effect. The effect of finite electron transport length on volume-phase hologram storage is analyzed. It is shown that the resulting holograms are spatially shifted relative to the optical-intensity pattern that produced it. This phase shift affects beam coupling during hologram reading; it can be an aid in studying the bulk photovoltaic effect and the relative importance of the various mechanisms of hologram writing. The analysis also points out that the finite electron transport length reduces the ability of the crystal to store holograms if the spatial frequency of the optical interference pattern is increased.

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Rumpf, Raymond C., Javier J. Pazos, Jennefir L. Digaum, and Stephen M. Kuebler. "Spatially variant periodic structures in electromagnetics." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, no. 2049 (August 28, 2015): 20140359. http://dx.doi.org/10.1098/rsta.2014.0359.

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Spatial transforms are a popular technique for designing periodic structures that are macroscopically inhomogeneous. The structures are often required to be anisotropic, provide a magnetic response, and to have extreme values for the constitutive parameters in Maxwell's equations. Metamaterials and photonic crystals are capable of providing these, although sometimes only approximately. The problem still remains about how to generate the geometry of the final lattice when it is functionally graded, or spatially varied. This paper describes a simple numerical technique to spatially vary any periodic structure while minimizing deformations to the unit cells that would weaken or destroy the electromagnetic properties. New developments in this algorithm are disclosed that increase efficiency, improve the quality of the lattices and provide the ability to design aplanatic metasurfaces. The ability to spatially vary a lattice in this manner enables new design paradigms that are not possible using spatial transforms, three of which are discussed here. First, spatially variant self-collimating photonic crystals are shown to flow unguided waves around very tight bends using ordinary materials with low refractive index. Second, multi-mode waveguides in spatially variant band gap materials are shown to guide waves around bends without mixing power between the modes. Third, spatially variant anisotropic materials are shown to sculpt the near-field around electric components. This can be used to improve electromagnetic compatibility between components in close proximity.

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Dúzs, Brigitta, and István Szalai. "Reaction–diffusion phenomena in antagonistic bipolar diffusion fields." Physical Chemistry Chemical Physics 24, no. 3 (2022): 1814–20. http://dx.doi.org/10.1039/d1cp04662d.

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The bipolar antagonistic diffusion field spatially localizes the intermediates of a reaction. This bipolar spatial control results in localized wave phenomena in a nonlinear activatory–inhibitory reaction.

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Pfeifer, Thomas W., John A. Tomko, Eric Hoglund, Ethan A. Scott, Khalid Hattar, Kenny Huynh, Michael Liao, Mark Goorsky, and Patrick E. Hopkins. "Measuring sub-surface spatially varying thermal conductivity of silicon implanted with krypton." Journal of Applied Physics 132, no. 7 (August 21, 2022): 075112. http://dx.doi.org/10.1063/5.0094876.

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The thermal properties of semiconductors following exposure to ion irradiation are of great interest for the cooling of electronic devices; however, gradients in composition and structure due to irradiation often make the measurement difficult. Furthermore, the nature of spatial variations in thermal resistances due to spatially varying ion irradiation damage is not well understood. In this work, we develop an advancement in the analysis of time-domain thermoreflectance to account for spatially varying thermal conductivity in a material resulting from a spatial distribution of defects. We then use this method to measure the near-surface ([Formula: see text]1 [Formula: see text]m) thermal conductivity of silicon wafers irradiated with Kr+ ions, which has an approximate Gaussian distribution centered 260 nm into the sample. Our numerical analysis presented here allows for the spatial gradient of thermal conductivity to be extracted via what is fundamentally a volumetric measurement technique. We validate our findings via transmission electron microscopy, which is able to confirm the spatial variation of the sub-surface silicon structure, and provide additional insight into the local structure resulting from the effects of ion bombardment. Thermal measurements found the ion stopping region to have a nearly 50[Formula: see text] reduction in thermal conductivity as compared to pristine silicon, while TEM showed the region was not fully amorphized. Our results suggest this drastic reduction in silicon thermal conductivity is primarily driven by structural defects in crystalline regions along with boundary scattering between amorphous and crystalline regions, with a negligible contribution being due to implanted krypton ions themselves.

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Sharon, Chelsea E., Andrew J. Baker, Andrew I. Harris, Dieter Lutz, and Linda J. Tacconi. "Spatial Variation of CO Excitation in High-z Galaxies." Proceedings of the International Astronomical Union 8, S292 (August 2012): 253. http://dx.doi.org/10.1017/s1743921313001282.

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AbstractPrevious studies of the molecular gas excitation in high-redshift galaxies have focused on galaxy-wide averages of CO line ratios. However, it is possible that these averages hide spatial variation on sub-galactic scales, disguising the true distribution and conditions of the molecular gas within star-forming galaxies. Even in the pre-ALMA era we have begun to see evidence for spatial variation of CO excitation in both rest-UV selected and submillimeter-selected galaxies at z > 2, aided both by the increased frequency coverage of the Jansky Very Large Array (allowing high-resolution observations of the CO(1–0) line, the best tracer for the coldest molecular gas) and by the benefits of gravitational lensing for spatially extended sources. We show new results for multiple high-redshift systems that reveal spatial and/or spectral variations in CO excitation, including an early-stage merger that has different conditions in its two components, thereby illustrating the need for high spatial and spectral resolution mapping in order to accurately characterize the molecular ISM in high-z galaxies.

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Tanaka, Shuta J. "Model of radio emission from spherically symmetric pulsar wind nebulae." Proceedings of the International Astronomical Union 8, S291 (August 2012): 511–13. http://dx.doi.org/10.1017/s1743921312024696.

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AbstractWe study radio emission from pulsar wind nebulae (PWNe) considering the observed spatial structure. We assume spherical symmetry of the PWN, and model the evolution of the magnetic field and the particle energy distribution. We do not consider the synchrotron cooling of particles but consider the adiabatic cooling, because we are mostly interested in the radio emission from PWNe. The model is applied to the Crab Nebula and succeeds to reproduce the observed spatially integrated spectrum in radio with a single power-law injection. In our previous work (a one-zone model), in contrast, the integrated spectrum of the Crab Nebula is reproduced by a broken power-law injection of particles. However, the spatial structure in radio is inconsistent with observations and we need a radial velocity profile which is very different from the model by Kennel & Coroniti. Further studies of the spatial structure of PWNe are important to understand the origin of the radio emission from young PWNe.

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Gorman, Martin G., Suzanne J. Ali, Peter M. Celliers, Jonathan L. Peebles, David J. Erskine, James M. McNaney, Jon H. Eggert, and Raymond F. Smith. "Measurement of shock roughness due to phase plate speckle imprinting relevant for x-ray diffraction experiments on 3rd and 4th generation light sources." Journal of Applied Physics 132, no. 17 (November 7, 2022): 175902. http://dx.doi.org/10.1063/5.0117905.

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Laser-shock compression experiments at 3rd and 4th generation light sources generally employ phase plates, which are inserted into the beamline to achieve a repeatable intensity distribution at the focal plane. Here, the laser intensity profile is characterized by a high-contrast, high-frequency laser speckle. Without sufficient smoothing, these laser non-uniformities can translate to a significant pressure distribution within the sample layer and can affect data interpretation in x-ray diffraction experiments. Here, we use a combination of one- and two-dimensional velocity interferometry to directly measure the extent to which spatial frequencies within the laser focal spot intensity pattern are smoothed out during propagation within the laser plasma and a polyimide ablator. We find that the use of thicker polyimide layers results in spatially smoother shock fronts, with the greatest degree of smoothing associated with the highest spatial frequencies. Focal spots with the smallest initial speckle separation produce the most rapid smoothing. Laser systems that employ smoothing by spectral dispersion techniques to rapidly modulate the focal plane intensity distribution are shown to be the most effective ones in producing a spatially smooth shock front. We show that a simple transport model combined with the known polyimide Hugoniot adequately describes the extent of shock smoothness as a function of polyimide thickness. Our results provide a description of spatial structure smoothing across a shock front, which can be used to design targets on x-ray free electron laser facilities.

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Hari, Pradip, Kevin Ko, Emmanouil Koukoumidis, Ulrich Kremer, Margaret Martonosi, Desiree Ottoni, Li-Shiuan Peh, and Pei Zhang. "SARANA: language, compiler and run-time system support for spatially aware and resource-aware mobile computing." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 366, no. 1881 (July 31, 2008): 3699–708. http://dx.doi.org/10.1098/rsta.2008.0127.

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Increasingly, spatial awareness plays a central role in many distributed and mobile computing applications. Spatially aware applications rely on information about the geographical position of compute devices and their supported services in order to support novel functionality. While many spatial application drivers already exist in mobile and distributed computing, very little systems research has explored how best to program these applications, to express their spatial and temporal constraints, and to allow efficient implementations on highly dynamic real-world platforms. This paper proposes the SARANA system architecture, which includes language and run-time system support for spatially aware and resource-aware applications. SARANA allows users to express spatial regions of interest, as well as trade-offs between quality of result (QoR), latency and cost. The goal is to produce applications that use resources efficiently and that can be run on diverse resource-constrained platforms ranging from laptops to personal digital assistants and to smart phones. SARANA's run-time system manages QoR and cost trade-offs dynamically by tracking resource availability and locations, brokering usage/pricing agreements and migrating programs to nodes accordingly. A resource cost model permeates the SARANA system layers, permitting users to express their resource needs and QoR expectations in units that make sense to them. Although we are still early in the system development, initial versions have been demonstrated on a nine-node system prototype.

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Lu, Fang-Wu, Quan-Gui Gao, and Li Zhang. "Energy-dependent nebula extent and spatially resolved spectra of the pulsar wind nebula 3C 58." Monthly Notices of the Royal Astronomical Society 498, no. 2 (September 16, 2020): 1911–19. http://dx.doi.org/10.1093/mnras/staa2338.

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ABSTRACT 3C 58 is a pulsar wind nebula (PWN) that shows an interesting energy-dependent nebula extent and spatial variations of the photon index and surface brightness in the X-ray band. These observations provide useful information with which to study the spatially dependent radiative cooling of electrons and the energy-dependent transport mechanisms within the nebula. In this paper, the energy-dependent nebula extent and spatially resolved spectra of this PWN are investigated in the framework of a spatially dependent particle transport model. The observations of the nebula, including the photon spectral energy distribution, spatial variations of the X-ray spectrum, and measurements of the nebula extent, can be naturally explained in this model. Our results show that the energy-dependent nebula extent favours an advection–diffusion scenario with advection-dominated transport, and the variations of the nebula extent with energy in the X-ray band can be attributed to the cooling losses of high-energy electrons affected by synchrotron burn-off. Particle diffusion plays an important role in modifying the spatial variations of the photon index and surface brightness in the X-ray band. The radial extents of the nebula at radio, GeV and TeV energies are predicted by the model, indicating that the nebula extent of 3C 58 varies with energy in these bands. The analyses show that the dependence of the adiabatic cooling rate and synchrotron radiation on the spectral index of injected particles is important for changing the nebula extent at different energies.

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Journal articles on the topic 'Astronomie spatiale'

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