Más allá del paisaje: análisis de los sistemas de fosas circulares neolíticas de la Baja Austria con arqueoastronomía virtual avanzada

[EN] This paper describes developments in virtual archaeology that started in a research project about the possible astronomical entrance orientation of Neolithic circular ditch systems (German Kreisgrabenanlagen, KGA) of Lower Austria. Starting from data analysis in a Geographical Information System (GIS), we will cover a simple way of modelling, and discuss three ways of visualisation for the combination of landscape and human-made buildings together with celestial objects. The first way involves extensions to the modelling program SketchUp to bring in just enough astronomical data for scientific evaluation. The second introduces a set of extensions to the open-source desktop planetarium program Stellarium, which can meanwhile be used to load a standard 3D model format to allow detailed research in astronomical orientation patterns, and light-and-shadow interaction over many millennia, even for researchers less familiar with astronomical programming. The third presents a “serious gaming” approach, which can provide the most natural view of the landscape, but requires at least some, if not deep, familiarity with astronomical and 3D computer graphics programming and, therefore, due to this considerably larger effort, appears to be mostly useful for outreach of high-profile results to the public. The entrances to the KGA of Lower Austria turned out to be mostly oriented following a purely terrestrial pattern of up- and downward sloping terrain, but with one noteworthy exception.Highlights:Virtual archaeology can help to better understand archaeological remains embedded in the landscape. Occasionally, the “landscape” concept must be extended to include the celestial landscape.Open-source development allowed the combination of a desktop planetarium with 3D landscape and architecture visualisation. Also, datable changes in the landscape can meanwhile be simulated.Astronomical elements added to a game engine can also be used to faithfully provide important insights while providing the most appealing visualisation environments so far, but with considerably more effort.[ES] Este artículo describe los desarrollos en el campo de la arqueología virtual que se iniciaron en un proyecto de investigación sobre la posible orientación astronómica de la entrada de los sistemas de fosas circulares neolíticas (Kreisgrabenanlagen en alemán, KGA) de Baja Austria. Partiendo del análisis de los datos en un Sistema de Información Geográfica (SIG), cubriremos una forma sencilla de modelización, y discutiremos tres formas de visualización para la combinación de los paisajes y los edificios construidos por el hombre junto con objetos celestes. La primera forma implica extensiones del programa de modelado SketchUp que aporta sólo los datos astronómicos necesarios para la evaluación científica. El segundo introduce un conjunto de extensiones al programa de sobremesa, de código abierto y de planetario denominado Stellarium, que pueden utilizarse para cargar un formato de modelo 3D estándar que permita la investigación detallada de patrones de orientación astronómica y la interacción luz-sombra a lo largo de muchos milenios, incluso a investigadores menos familiarizados con la programación astronómica. El tercero presenta un enfoque de "juego serio", que puede proporcionar la visión más natural del paisaje, pero que requiere al menos cierta, si no profunda, familiaridad con la programación astronómica y de gráficos por ordenador en 3D y, por lo tanto, debido a este esfuerzo considerablemente mayor, parece ser mayormente útil para la divulgación de resultados destacados al público. 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Smartphone Based 3D Navigation Techniques in an Astronomical Observatory Context: Implementation and Evaluation in a Software Platform

International audience3D Virtual Environments (3DVE) come up as a good solution to transmit knowledge in a museum exhibit. In such contexts, providing easy to learn and to use interaction techniques which facilitate the handling inside a 3DVE is crucial to maximize the knowledge transfer. We took the opportunity to design and implement a software platform for explaining the behavior of the Telescope Bernard-Lyot to museum visitors on top of the Pic du Midi. Beyond the popularization of a complex scientific equipment, this platform constitutes an open software environment to easily plug different 3D interaction techniques. Recently, popular use of a smartphones as personal handled computer lets us envision the use of a mobile device as an interaction support with these 3DVE. Accordingly, we design and propose how to use the smartphone as a tangible object to navigate inside a 3DVE. In order to prove the interest in the use of smartphones, we compare our solution with available solutions: keyboard-mouse and 3D mouse. User experiments confirmed our hypothesis and particularly emphasizes that visitors find our solution more attractive and stimulating. Finally, we illustrate the benefits of our software framework by plugging alternative interaction techniques for supporting selection and manipulation task in 3D

Weak gravitational lensing : Detection of mass concentrations in wide field imaging data

The deflection and distortion of a light bundle by tidal gravitational fields is described in the framework of General Relativity. There, light bundles from a source follow exactly the curvature of spacetime, and are distorted when passing by a large mass concentration such as a galaxy cluster. This weak gravitational lensing effect can be used to reconstruct the (dark) matter distribution in the lens, and to obtain a mass estimate independent of its luminosity and virialisation. A description of the basic (cosmological) physics behind gravitational lensing is given in the first Chapter of the present work, together with an introduction into the subject of gravitational lensing itself. With the rapid improvement of detector and telescope technology, and the advent of wide field imagers at the end of the nineties, it became possible to turn the lensing argument around and use the weak lensing effect to search for mass concentrations in the universe. This method has the advantage that the galaxy clusters are detected directly by their most fundamental property, the mass, and not by their luminosity. The mass of a cluster, in turn, is a sensitive measure of cosmology and thus a mass-selected sample of galaxy clusters is highly desireable in this respect. A significant fraction of clusters detected in this way is rather enigmatic, since they appear to be entirely dark, i.e. they are not associated with any light. The physical nature of these objects, if they are indeed real and not due to some yet unknown systematics, is still unclear. This work establishes for the first time a larger sample of such objects. For the latter purpose, our group conducted a weak lensing survey with the Wide Field Imager at the 2.2m MPG/ESO telescope. 20 square degrees of the southern sky were mapped to great depth in excellent observational conditions. For the reduction of the very large amount of data (several TB), a fully automatic pipeline had to be developed that meets all specifications required for an analysis of the weak lensing effect. Four men years were used for the development and thorough testing of this tool. A description of the pipeline and the techniques required especially for multi-chip cameras is given in Chapter 2. In Chapter 3 the focus of interest is on the analysis of the reduced images, and the extraction of the desireable weak lensing signal. The basic quantity which is to be obtained from the images are the shapes of the potentially lensed galaxies, which is a highly non-trivial task as is outlined in the text. Having measured image shapes at hand, a statistics is introduced that allows the identification of a distortion pattern characteristic for galaxy clusters, and an estimate of the signal-to-noise of its detection. This statistics involves a filter function, for which several suggestions are given in the literature. Further possibilities are introduced in this work, and the various filters are tested extensively against each other. A very effective new filter was found in this process for the detection of mass concentrations. Chapter 4, finally, verifies the used evaluation methods and presents the results obtained from the conducted survey. It is shown that the galaxies in the survey fields are not randomly oriented, but show significant coherent shear patterns, which are consistent with simulations. Besides, a sample of 100 mass concentrations with a signal-to-noise of at least 4 is presented. About 60% of the mass concentrations found are dark, whereas 30% are bright, having obvious optical counterparts. Half of the latter are already spectroscopically confirmed. The remaining 10% of the sample could not be classified. The populations of the bright and dark mass peaks show very similar distributions in their size as well as in their significance, apart from the very smallest angular scale probed where disproportionate many dark peaks are found. It is shown that true mass peaks can be discerned from spurious peaks in the sense that they appear on a significant level for a broader range of filter scales. Thereafter, various verification methods for the mass detections found are presented by means of an example

High cadence optical polarimetry for time domain astronomy on the Liverpool Telescope

Gamma-ray bursts are the most violent of known astrophysical events, with up to 10^53 ergs of energy released on the order of seconds. These extreme explosions, first observed in 1960s, form a fast moving field of research within astrophysics which relies on multi-wavelength observations of these transient events to probe the early- time (< 15 minutes) parameter space of these events. In the optical regime, follow-up observations to the prompt emission are ideally suited to the 2.0 metre Liverpool Tele- scope (LT), situated at an altitude of 2363m on the Observatorio Roque de las Mucha- chos (ORM), La Palma, Canary Islands. The LT is fully robotic and able to respond automatically to triggers of new gamma-ray burst (GRB) events, starting within 2-3 minutes of the detection of the prompt emission. The observed radiation from GRBs is released from relativistic jets. Launched from a black hole central engine, the energy within the jets is converted to the observed radi- ation predominantly through a synchrotron process, which can produce highly linearly polarised radiation. Polarimetric observations of this radiation are a key resource to infer the magnetic field structure of the emission region and distinguish between baryonic and magnetic models of jet physics. For this reason, the Liverpool Telescope has hosted the RINGO series of polarimeters which use a novel design to enable early-time polarimetric measurements of these highly variable optical sources. RINGO was mounted on the LT in 2005, and observed GRB 090102A providing a measure of 10.2 ± 1.3% average linear polarisation in the period of 160-220s post burst. RINGO2, mounted in June 2009 improved on the original design utilising a triggered electron multiplying CCD system. Both RINGO and RINGO2 were single band instruments. The development of RINGO3 extended the design of RINGO2 into a simultaneous 3 band polarimeter. This work focuses on the characterisation of RINGO2 and analysing the sample of GRB observations made during its lifetime. The observations of GRB 120308A provide measurements with a high confidence, inferring the existence of stable, or- dered magnetic fields within the jet. Analysis of other GRB afterglows observed with RINGO2 provides confidence in this result and confirm that jets can be highly magne- tised, with the majority of energy being contained in magnetic field recombination and not through kinetic energy of baryonic matter. RINGO3, a multi-band extension to RINGO2, was developed and tested within the Astrophysics Research Institute labs before being commissioned on the Liverpool Telescope in November 2012. Lab tests of instrument throughput with calculations of the signal to noise ratio across the operating wavelength defined the optimal cut-offs of the 3 wavelength bands. This instrument was then characterised using similar methods to RINGO2, and whilst not an ideal instrument was found to be within the required performance for the prime science goal of early-time GRB afterglow observations

Probing dark energy with large-scale galaxy clustering: from instrumentation to simulation

In the standard paradigm of cosmology, everything we observe now originated from initial quantum fluctuations in a small smooth region, which were frozen in during inflation and became primordial density perturbations on large classical scales. Under gravitational collapse, the overdensities seeded the formation of stars and galaxies. Mapping the large-scale structure of the universe at the Cosmic Frontier is a promising experimental avenue which will address in the next decade several pressing open questions in cosmology and particle physics, most notably the accelerating cosmic expansion. The observed distribution of galaxies and quasars traces the underlying matter density field and contains a wealth of information from signatures of primordial conditions to the background evolution rate. The Dark Energy Spectroscopic Instrument (DESI) is a next-generation, Stage IV dark energy experiment that will measure the expansion history of the universe through baryon acoustic oscillations and the growth of structure through redshift-space distortions with unprecedented precision. Ground-based at the Kitt Peak National Observatory, DESI features a new 8 deg² field-of-view corrector, 5000 robotically-actuated fibre positioners, and ten fibre-fed spectrographs. The 5-year survey beginning in 2020 will measure the spectra of 35 million galaxies and quasars up to redshift z ~ 3.5 in the 360 nm to 980 nm wavelength range, covering 14000 deg² of the sky. With an order of magnitude improvement over previous redshift surveys, DESI will place tight constraints on the dark energy equation of state, modified gravity, the existence of extra light species, neutrino masses, and models of inflation. ProtoDESI was a proof of concept commissioned in 2016 to mitigate the risks associated with DESI's challenging instrument design and precision requirements. Its simplified focal plane instrument housed 3 fibre positioners and a fibre photometry camera in place of spectrographs. ProtoDESI was successful as the first on-sky technology demonstration for DESI. For the official DESI focal plane instrument, the fibre positioning accuracy and, ultimately, the success of DESI, are grounded upon the stringent specifications of the focal plate structure (FPS) which directly holds the positioners. The FPS parts, consisting of ten focal plate petals (FPPs) and a focal plate ring, were fabricated with the required tolerances, comprehensively inspected, and aligned with appropriate shims and gauge blocks to ensure minimal loss of photons at the fibre tips. Adopting a coordinate measurement machine-based approach, we projected the fibre injection efficiency by measuring hardware features and modelling geometric transformations and fibre optics. The as-aligned, total root-mean-square optical throughput for 6168 positioner holes of 12 production FPPs (including two spares) is 99.88% ± 0.12%, well above the 99.5% project requirement. Finally, observations of galaxy clustering cannot be properly understood alone without accompanying theoretical motivations and numerical simulations in parallel. Cosmological N-body simulations have become indispensable for designing survey strategies, developing analysis methods, and making theoretical predictions. We quantify the shifts of the acoustic scale potentially resulting from galaxy clustering bias, which constitutes an increasingly significant source of theoretical systematics in distance measurements with the standard ruler. Utilising mock catalogues based on generalised halo occupation population of high-accuracy Abacus simulations in the largest volume to date for such tests, 48h⁻¹Gpc³, we find a 0.3% shift in the line-of-sight acoustic scale for one variation in the satellite galaxy population and a 0.7% shift for an extreme level of velocity bias of the central galaxies, while other models tested are consistent with zero shift at the 0.2% level after reconstruction. We note that these bias models produce sizeable and likely distinguishable changes at small scales that correlate with the shifts

Comets as natural laboratories: Interpretations of the structure of the inner heliosphere

Comets can be considered to be natural laboratories of the inner heliosphere, as their ion tails trace the solar wind flow. Much has been learnt about the heliosphere’s structure from in situ solar wind spacecraft observations. Their coverage is however limited in time and space. This thesis proposes to address these constraints and ascertain the validity of analysing comets’ ion tails as complementary sources of information on dynamical heliospheric phenomena and the underlying continuous solar wind. Solar wind conditions influence comets’ induced magnetotails, formed through the draping of the heliospheric magnetic field by the velocity shear in the mass-loaded solar wind. I present a novel imaging technique and software to exploit the vast catalogues of amateur and professional images of comet ion tails. My projection technique uses the comet’s orbital plane to sample its ion tail as a proxy for determining radial solar wind velocities in each comet’s vicinity. Making full use of many observing stations from astrophotography hobbyists to professional observatories and spacecraft, this approach is applied to several comets observed in recent years. Complementary velocities, derived from folding ion rays and a velocity profile map built from consecutive images, are provided as an alternative means of quantifying the solar wind-cometary ionosphere interaction. I review the validity of these techniques by comparing near-Earth comets to solar wind models in the inner heliosphere and extrapolated measurements by ACE to a near-Earth comet’s orbit. My radial velocities are mapped back to the solar wind source surface to identify sources of the quiescent solar wind and heliospheric current sheet crossings. Comets are found to be good indicators of solar wind structure, but the quality of results is strongly dependent on the observing geometry. Many ion tails also show a constant curvature, so far unexplained, which further complicates the interpretation of tails’ orientations

Realistic visualisation of cultural heritage objects

This research investigation used digital photography in a hemispherical dome, enabling a set of 64 photographic images of an object to be captured in perfect pixel register, with each image illuminated from a different direction. This representation turns out to be much richer than a single 2D image, because it contains information at each point about both the 3D shape of the surface (gradient and local curvature) and the directionality of reflectance (gloss and specularity). Thereby it enables not only interactive visualisation through viewer software, giving the illusion of 3D, but also the reconstruction of an actual 3D surface and highly realistic rendering of a wide range of materials. The following seven outcomes of the research are claimed as novel and therefore as representing contributions to knowledge in the field: A method for determining the geometry of an illumination dome; An adaptive method for finding surface normals by bounded regression; Generating 3D surfaces from photometric stereo; Relationship between surface normals and specular angles; Modelling surface specularity by a modified Lorentzian function; Determining the optimal wavelengths of colour laser scanners; Characterising colour devices by synthetic reflectance spectra

COSMOLOGICAL NARRATIVE IN THE SYNAGOGUES OF LATE ROMAN-BYZANTINE PALESTINE

The night sky provided ancient peoples with a visible framework through which they could view and experience the divine. Ancient astronomers looked to the night sky for practical reasons, such as the construction of calendars by which time could evenly be divided, and for prognosis, such as the foretelling of future events based on the movements of the planets and stars. While scholars have written much about the Greco-Roman understanding of the night sky, few studies exist that examine Jewish cosmological thought in relation to the appearance of the Late Roman-Byzantine synagogue Helios-zodiac cycle. This dissertation surveys the ways that ancient Jews experienced the night sky, including literature of the Second Temple (sixth century BCE – 70 CE), rabbinic and mystical writings, and Helios-zodiac cycles in synagogues of ancient Palestine. I argue that Judaism joined an evolving Greco-Roman cosmology with ancient Jewish traditions as a means of producing knowledge of the earthly and heavenly realms.Doctor of Philosoph

Developing a multiple glazing system to minimize transmission of direct insolation for particular latitudes

Too often, in the last 50 years, the energy-thrift lessons of vernacular architecture have been forgotten or ignored. In the Middle East, many recently-designed commercial buildings, with large areas of glazing, incur excessively high electricity-demands to provide energy for the required air-conditioning plant. One way of reducing the magnitude of this demand is through better window design. A new glazing system is proposed that utilizes the insertion of a clear glazing element within the cavity of a double glazed window. The main objective of this system is to achieve acceptable levels of daylight within a building by attempting to maintain the diffuse component of insolation while reducing the penetration of direct component by using the increased reflectivity of these materials with the angle of incidence of the direct beam component of solar irradiation. By using clear glazing materials the proposed system attempts to achieve acceptable performance without the need for elaborate and expensive coatings or substrates. Because solar geometry varies with latitude a varying performance of glazing systems is expected with current glazing systems. However, the suggested system utilizes an optimal angle for overall daylighting and thermal performance that relates to the particular solar geometry of interest, New software is also developed to assess the performance of the suggested system; this involved examining all the modes of heat transfer through the entire glazing system. Results then were assessed to calculate the optimal angle of the element that corresponds to the solar geometry of particular latitude. Such proposal takes a new perspective, once it is acknowledged that though different forms of advanced glazing systems currently are being used to inhibit the penetration of direct solar radiation, still the main disadvantages of such advanced glazing systems are that they are relatively expensive and would reduce the penetration of a considerable part of the daylight entering the space