CANDELS: The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey - The Hubble Space Telescope Observations, Imaging Data Products and Mosaics

This paper describes the Hubble Space Telescope imaging data products and data reduction procedures for the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS). This survey is designed to document the evolution of galaxies and black holes at $z\sim1.5-8$, and to study Type Ia SNe beyond $z>1.5$. Five premier multi-wavelength sky regions are selected, each with extensive multiwavelength observations. The primary CANDELS data consist of imaging obtained in the Wide Field Camera 3 / infrared channel (WFC3/IR) and UVIS channel, along with the Advanced Camera for Surveys (ACS). The CANDELS/Deep survey covers \sim125 square arcminutes within GOODS-N and GOODS-S, while the remainder consists of the CANDELS/Wide survey, achieving a total of \sim800 square arcminutes across GOODS and three additional fields (EGS, COSMOS, and UDS). We summarize the observational aspects of the survey as motivated by the scientific goals and present a detailed description of the data reduction procedures and products from the survey. Our data reduction methods utilize the most up to date calibration files and image combination procedures. We have paid special attention to correcting a range of instrumental effects, including CTE degradation for ACS, removal of electronic bias-striping present in ACS data after SM4, and persistence effects and other artifacts in WFC3/IR. For each field, we release mosaics for individual epochs and eventual mosaics containing data from all epochs combined, to facilitate photometric variability studies and the deepest possible photometry. A more detailed overview of the science goals and observational design of the survey are presented in a companion paper.Comment: 39 pages, 25 figure

EG Andromedae: A Symbiotic System as an Insight into Red Giant Chromospheres

Symbiotic systems are interacting binary stars consisting of both hot and cool components. This results in a complex environment that is ideal for studying the latter stages of stellar evolution along with interactions within binary systems. As a star approaches the end of its life, in particular the red giant phase, it exhausts its supply of core hydrogen and begins burning its way through successively heavier elements. Red giants lose mass in the form of a dense wind that will replenish the interstellar medium with chemical elements that are formed through nuclear processes deep in the stellar interior. When these elements reach the interstellar medium they play a central role in both stellar and planetary evolution, as well as providing the essential constituents needed for life. The undoubted significance of these cool giants means the study of their atmospheres is necessary to help understand our place in the Universe. This thesis presents Hubble Space Telescope observations of the symbiotic system EG Andromedae as an insight into red giant stars. EG And is one of the brightest and closest symbiotic systems and consists of a red giant primary along with a white dwarf. The presence of the white dwarf in the system allows spatially resolved examination of the red giant primary. The benefits of using such a system to better understand the base of red giant chromospheres is shown. Along with the observations of EG And, new HST observations of an isolated red giant spectral standard HD148349 are described. The similarity between the isolated spectral standard and the red giant primary of EG And is demonstrated, showing that much of the information gleaned from a symbiotic system can be applied to the general red giant population. Using both ultraviolet and optical spectroscopy, the atmosphere of EG And and HD148349 are investigated and contrasted.Comment: PhD Thesis, Trinity College Dubli

GPU data structures for graphics and vision

Graphics hardware has in recent years become increasingly programmable, and its programming APIs use the stream processor model to expose massive parallelization to the programmer. Unfortunately, the inherent restrictions of the stream processor model, used by the GPU in order to maintain high performance, often pose a problem in porting CPU algorithms for both video and volume processing to graphics hardware. Serial data dependencies which accelerate CPU processing are counterproductive for the data-parallel GPU. This thesis demonstrates new ways for tackling well-known problems of large scale video/volume analysis. In some instances, we enable processing on the restricted hardware model by re-introducing algorithms from early computer graphics research. On other occasions, we use newly discovered, hierarchical data structures to circumvent the random-access read/fixed write restriction that had previously kept sophisticated analysis algorithms from running solely on graphics hardware. For 3D processing, we apply known game graphics concepts such as mip-maps, projective texturing, and dependent texture lookups to show how video/volume processing can benefit algorithmically from being implemented in a graphics API. The novel GPU data structures provide drastically increased processing speed, and lift processing heavy operations to real-time performance levels, paving the way for new and interactive vision/graphics applications.Graphikhardware wurde in den letzen Jahren immer weiter programmierbar. Ihre APIs verwenden das Streamprozessor-Modell, um die massive Parallelisierung auch für den Programmierer verfügbar zu machen. Leider folgen aus dem strikten Streamprozessor-Modell, welches die GPU für ihre hohe Rechenleistung benötigt, auch Hindernisse in der Portierung von CPU-Algorithmen zur Video- und Volumenverarbeitung auf die GPU. Serielle Datenabhängigkeiten beschleunigen zwar CPU-Verarbeitung, sind aber für die daten-parallele GPU kontraproduktiv . Diese Arbeit präsentiert neue Herangehensweisen für bekannte Probleme der Video- und Volumensverarbeitung. Teilweise wird die Verarbeitung mit Hilfe von modifizierten Algorithmen aus der frühen Computergraphik-Forschung an das beschränkte Hardwaremodell angepasst. Anderswo helfen neu entdeckte, hierarchische Datenstrukturen beim Umgang mit den Schreibzugriff-Restriktionen die lange die Portierung von komplexeren Bildanalyseverfahren verhindert hatten. In der 3D-Verarbeitung nutzen wir bekannte Konzepte aus der Computerspielegraphik wie Mipmaps, projektive Texturierung, oder verkettete Texturzugriffe, und zeigen auf welche Vorteile die Video- und Volumenverarbeitung aus hardwarebeschleunigter Graphik-API-Implementation ziehen kann. Die präsentierten GPU-Datenstrukturen bieten drastisch schnellere Verarbeitung und heben rechenintensive Operationen auf Echtzeit-Niveau. Damit werden neue, interaktive Bildverarbeitungs- und Graphik-Anwendungen möglich

NEW INSIGHTS ON THE INNER MASS DISTRIBUTION OF MASSIVE GALAXY CLUSTERS FROM A COMBINATION OF STRONG LENSING AND GALAXY KINEMATICS

Galaxy clusters are important astrophysical laboratories to study the nature of Dark Matter (DM), whose physical properties are still unknown. In particular, a detailed investigation of the mass distribution of cluster halos, by dissecting the DM and baryonic components, can provide stringent tests of the Cold Dark Matter paradigm of structure formation. Over the last decade, strong gravitational lensing has become one of the most powerful techniques to study the total mass distribution in the Universe, particularly on galaxy and cluster scale. In recent years, dedicated large imaging surveys with HST and ground-based spectroscopic campaigns on sizeable samples of massive galaxy clusters have ushered a new generation of high-precision strong lensing models, via the identification of a large number of multiple images and cluster members. In this thesis, we extend beyond the state of the art these new cluster lens models, including the stellar kinematics of a significant fraction of cluster galaxies measured with the integral field spectrograph MUSE on the VLT. This study focuses on three massive clusters MACS~J1206.2$-$0847, MACS~J0416.1$-$2403, and Abell S1063 at $zsim 0.4$ with HST imaging and VLT spectroscopy data of unprecedented quality. Specifically, we measured the stellar velocity dispersion, $sigma$, of 40-60 member galaxies per cluster with MUSE, covering 4-5 magnitudes down to $mF160W simeq 21.5$. The robustness and accuracy of the velocity dispersion measurements were tested with extensive spectral simulations. We determined the normalization and slope of the galaxy Faber-Jackson relation in each cluster, and include this prior information in the cluster lens models. We find that using this novel technique, the inherent degeneracy between different mass components and possible systematics on model parameters are strongly reduced and the mass density profiles of the cluster galaxies are now robustly constrained. Once re-normalized to the same absolute luminosity, our kinematic lens models predict consistent masses and sizes of sub-halos as a function of galaxy velocity dispersions. Moreover, extending previous findings, we derive consistent sub-halo mass velocity dispersion functions for the three clusters. By comparing the observed sub-halo mass distribution from our cluster lens models with the predictions of high-resolution N-body and hydrodynamical cosmological simulations, we find a lack of compact sub-structures in the corresponding inner regions of simulated clusters, whereas the sub-halo mass functions are found in good agreement. We still do not understand whether the origin of these differences has to be ascribed to numerical or resolution effects in the simulations, or to some physical aspect missing in the Cold Dark Matter framework. An additional method to investigate the mass distribution of cluster galaxies is to exploit galaxy scale strong lensing systems (GSSLS), in which a single cluster galaxy produces highly magnified multiple images on kpc scale around lens galaxies. We show how strong lensing modeling of GSSLS in the cluster field, in combination with spatially resolved stellar kinematics of the lens galaxies, can further constrain the structure and sizes of cluster sub-halos. Finally, in an effort to include in our lens models the measured cluster member stellar velocity dispersions and the observed scatter of the Faber-Jackson relation, we develop and made public a python module that expands the capabilities of common lens modeling tools. The methodology of high-precision lens modeling developed in this thesis will find important applications in the near future when large numbers of cosmic lenses will be discovered with large-area surveys. In particular, by exploiting lensing clusters as powerful cosmic telescopes to investigate galaxies in the early Universe and in cosmographic applications with gravitational time delay techniques

The 2005 HST Calibration Workshop Hubble After the Transition to Two-Gyro Mode

The 2005 HST Calibration Workshop was held at the Space Telescope Science Institute during October 26, 2005 to bring together members of the observing community, the instrument development teams, and the STScI instrument support teams to share information and techniques. Presentations included the two-gyro performance of HST and FGS, advances in the calibration of a number of instruments, the results of other instruments after their return from space, and the status of still others which are scheduled for installation during the next servicing mission. Cross-calibration between HST and JWST was discussed, as well as the new Guide Star Catalog and advances in data analysis software. This book contains the published record of the workshop, while all the talks and posters are available electronically on the workshop Web site

Characterization of microplastics and natural gas by infrared spectrometry and multivariate modelling

Programa Oficial de Doutoramento en Ciencia e Tecnoloxía Ambiental. 5006V01[Abstract] The main objective of this work is to explore the use of infrared spectrometry combined with the application of multivariate chemometric models to the quantification of the major components of natural gas and to the identification of plastic samples, both artificially aged and collected from coastal ecosystems. The articles presented here deal with different themes related with these topics. In particular: the application of IR-inert gases to improve the spectra of other gases of interest; a report evidencing a general absence of important specifications of the instrumental setup of environmental studies on microplastics, suggesting a minimum of information to be offered; and a study of the effects of aging in both the surface morphology and the spectral characteristics of polyamide 6.6. Finally, chemometric models have been developed to identify the main constituent polymers of microplastics and to quantify the major components of natural gas samples, as well as their Wobbe index.[Resumen] El principal objetivo de este trabajo es explorar el uso de la espectrometría infrarroja combinada con la aplicación de modelos quimiométricos multivariables para cuantificar de la composición mayoritaria de muestras de gas natural y para identificar muestras de plásticos, tanto envejecidos de forma artificial como recolectados de ecosistemas costeros. Los artículos presentados tratan sobre diversos aspectos relacionados con estos temas. En concreto: el uso de gases inertes a la radiación infrarroja para mejorar los espectros de otros gases de interés; un informe que evidenciando una importante ausencia de especificaciones instrumentales básicas en los estudios medioambientales sobre microplásticos, donde se sugiriere un mínimo de información a aportar; y un estudio de los efectos del envejecimiento en la morfología y características espectrales de la poliamida 6.6. Finalmente, se han desarrollado modelos quimiométricos capaces de identificar los principales polímeros constituyentes de microplásticos y de cuantificar los componentes mayoritarios de muestras de gas natural, así como su índice Wobbe.[Resumo] O obxectivo principal deste traballo é explorar o uso da espectrometría infravermella combinada coa aplicación de modelos quimiométricos multivariabeis para a cuantificación da composición maioritaria de mostras de gas natural e a identificación de plástico, tanto envellecidos artificialmente como recollido de ecosistemas costeiros. Os diferentes artigos presentados tratan diversos aspectos relacionados con estes temas. Nomeadamente: a aplicación de gases inertes á radiación infravermella para mellorar os espectros doutros gases de interese; unha recompilación onde se constata a ausencia xeral especificacións instrumentais fundamentais nos estudos medioambientais de microplásticos, suxerindo un mínimo de información a aportar; e un estudo dos efectos do envellecemento na morfoloxía e características espectrais na poliamida 6.6. Finalmente, desenvolvéronse modelos quimiométricos capaces de identificar os polímeros constituíntes de microplásticos e de cuantificar os principais compoñentes de mostras de gas natural, ademais do seu índice de Wobbe

Gas flows and star formation as a consequence of galaxy interaction in compact groups

The environment of galaxies is known to influence their evolution via a wide range of processes, such as tidal interactions, ram-pressure stripping, or galaxy harassment. However, the exact interconnectivity between the large scale environment-driven mechanisms and the other internal processes (starburst, star formation quenching, nuclear activity, and both outflows and inflows) remains poorly understood. This thesis describes the use of the WiFeS and MUSE integral field spectrographs to study gas flows and star formation activity inside two members of compact groups of galaxies: HCG 16c and HCG 91c. In particular, WiFeS and MUSE are used to resolve scales of 1 kpc at the distances of HCG 16c and HCG 91c - the size of giant molecular clouds and HII regions - in an effort to tie the environment to its impact within the disks of the galaxies. HCG 16c is found to host an asymmetric, bipolar, rotating galactic wind, powered by a nuclear starburst. Emission line ratio diagnostics indicate that photoionization is the dominant excitation mechanism at the base of the wind. The asymmetry of the wind is likely caused by one of the two lobes of the wind-blown bubble bursting out of its HI envelope. The characteristics of the wind suggest that it is caught early (a few Myr) in the wind evolution sequence. The wind is also quite different to the galactic wind in the partner galaxy HCG 16d which contains a symmetric, shock-excited wind. Given that both galaxies have (likely) similar interaction histories, the different wind characteristics must be a consequence of the intrinsic properties of HCG 16c and HCG 16d. In HCG 91c, WiFeS and MUSE reveal HII regions with kinematic and abundance offsets in this otherwise unremarkable star-forming spiral. Specifically, at least three HII regions harbor an oxygen abundance 0:15 dex lower than expected from their immediate surroundings and from the overall abundance gradient present in the disk of this galaxy. The same star forming regions are also associated with a small kinematic offset in the form of a lag of 5-10kms1 with respect to the local circular rotation of the gas. HI observations of HCG 91 from the VLA and broadband optical images from Pan-STARRS suggest that HCG 91c is caught early in its interaction with the compact group HCG 91. Altogether, evidence point towards infalling and collapsing extra-planar halo gas clouds at the disk-halo interface of the galaxy. As such, HCG 91c provides evidence that some of the perturbations possibly associated with the early phase of galaxy evolution in compact groups impact the star forming disk locally, and on sub-kpc scales. Finally, this thesis also describes a series of new tools developed for the processing, analysis and visualization of these integral field spectroscopy datasets. These comprise a new data reduction pipeline for the WiFeS instrument, interactive PDF & HTML documents for multi-dimensional data visualization and publication, 3-D printing of astrophysical datasets, the pyqz code to derive oxygen abundances & ionization parameters from strong emission line ratios, and 3-D line ratio diagnostic diagrams

Physical mechanisms controlling the pre-failure stress-strain behavior of frozen sand

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.Includes bibliographical references.The physical mechanisms controlling the pre-failure stress-strain behavior of frozen sands are investigated in triaxial compression. The pre-failure, or small strain behavior (Ea<l%), is represented by the initial stiffness (Young's modulus) and the upper yield stress, a very distinctive yield point representing the onset of large unrecoverable plastic strains. An extensive experimental program was conducted on a number of ice-saturated particulate systems to investigate the dependency of these two parameters on volume fraction, stress level, strain rate, and temperature, as well as on particle size, stiffness, roughness, shape, and interfacial bond strength. Theories for composite material behavior are employed to analyze the observed stress-strain-time-temperature behavior. The stress-strain behavior has been measured in a high-pressure, low-temperature automated triaxial compression testing system. Strain was evaluated using a novel on-specimen measurement device capable of consistently resolving displacements of less than 0.1 microns, corresponding to strains of less than 0.0002% for specimens measuring 3.6 cm x 7.6 cm. Very precise temperature and strain rate control systems contributed to the reliability of the small strain measurements at confining pressures up to 10 MPa. Experimental findings show that the Young's modulus of frozen soils varies significantly with particle modulus and increases slightly with particle volume fraction, but does not change with strain rate and temperature. The development of stiffness, however, relies heavily on the extent of coupling between phases for the effective transfer of shear stress. This coupling can take the form of an adhesional bond or a frictional bond. In natural sand systems, shear stress is transferred through surface roughness and particle angularity and consequently the presence of an adhesional bond is not important. However, adhesional bonding is much more important in systems composed of smooth spherical particles. Application of reinforcement theories for two-phase particulate composites has led to a new approach for predicting the Young's modulus of frozen sand. The upper yield stress behavior is controlled primarily by strain rate, temperature, and particle grain size, and for fully-bonded materials, is essentially independent of particle volume fraction and stress level. In the absence of an adhesional bond, however, the degree of surface roughness and stress level affect the upper yield stress of the system, showing the importance of coupling in this region as well. The qualitative behavior of the upper yield stress relative to polycrystalline ice can be explained by examining the influence of ice-particle interaction on the nature of cracks propagating through the ice matrix.by Gregory Da Re.Ph.D