Finalized PhD theses

Nombre d'entrades: 84

Measuring Large Scale Structure using angular cross-correlations

Estat: defended (27/09/2013)
Estudiant: Jacobo Asorey Barreiro
Supervisat per: Enrique Gaztañaga ; Martin Crocce
Universitat: Universitat Autònoma de Barcelona

La propuesta de proyecto de tesis se enmarca en el estudio de la evolución cósmica a través de cartografiados extragalácticos. Será llevada a cabo dentro del grupo de Cosmología del Instituto de Ciencias del Espacio (IEEC-CSIC), el cual participa activamente en la construcción de grandes cartografiados como son el Physics of the Accelerating Universe Survey (PAU Survey), el Dark Energy Survey (DES) y el ESA-EUCLID. El proyecto consistirá en estudiar y entender la ciencia básica relacionada con los catálogos de galaxias resultantes de tales cartografiados, además de desarrollar métodos de análisis que nos permitan optimizar la información sobre el contenido de materia y energía del Universo, que condicionan tanto la evolución cósmica como la formación de estructuras a grandes escalas. Esto nos permitiría discriminar entre diferentes modelos, tanto los que se basan en la energía oscura como el fluido responsable de la expansión acelerada del Universo como aquellos que proponen modificaciones de la teoría de la gravedad para explicar dicha aceleración. Para ello tendremos en cuenta la distribución espacial de las galaxias, las distorsiones en el espacio de redshift producidas por el campo de velocidades de las galaxias y el efecto de lente gravitatoria causado sobre las imágenes de galaxias más lejanas por la materia que hay entre nosotros y dichas fuentes. Especialmente, en el caso de PAU, al basarse en la estimación de coordenadas radiales de las galaxias usando redshifts fotométricos de alta resolución, mediante la toma de imágenes de las galaxias contenidas en el volumen del catálogo con una cámara con 40 filtros de banda estrecha, estudiaremos la manera óptima de analizar el catálogo que resulte cuando finalice el cartografiado al tratarse de una nueva técnica observacional para la obtención de cartografiados extragalácticos. La obtención del redshifts fotométricos de alta resolución, nos permite dividir en capas muy finas el volumen del catálogo, pudiendo estudiar como están correlacionadas las galaxias en cada capa y entre ellas, abriendo nuevos horizontes en el análisis de la distribución de galaxias y materia oscura. Además será posible llegar hasta una profundidad de z ~ 1.2 lo que también amplia la capacidad de posibles análisis. Se realizarán predicciones de los errores estadísticos a los que estarán sujetos los cartografiados en construcción utilizando métodos analíticos, numéricos e incluso simulaciones cosmológicas. Así mismo, se aplicarán las herramientas desarrolladas en los datos una vez disponibles. En particular intentaremos desarrollar técnicas que nos permitan combinar los relacionados a los catálogos de galaxias con datos procedentes de otros experimentos como son el espectro de anisotropías en la temperatura de la radiación de fondo de microondas dados por WMAP o Planck o catálogos de Supernovas de tipo Ia. Un objetivo final es realizar una determinación de parámetros conjunta que nos permita obtener todavía mayor precisión en la determinación del contenido energético del Universo y en la parametrización de la Energía Oscura.
In this thesis we propose to use galaxy clustering, more concretely angular cross-correlations, as a tool to understand the late-time expansion of the Universe and the growth of large-scale structure. Galaxy surveys measure the position of galaxies (what traces the dark- matter field) in spherical coordinates…
Estat: defended (27/09/2013)
Estudiant: Jacobo Asorey Barreiro
Supervisat per: Enrique Gaztañaga ; Martin Crocce
Universitat: Universitat Autònoma de Barcelona

In this thesis we propose to use galaxy clustering, more concretely angular cross-correlations, as a tool to understand the late-time expansion of the Universe and the growth of large-scale structure. Galaxy surveys measure the position of galaxies (what traces the dark- matter field) in spherical coordinates (z,θ,φ). Most galaxy clustering analyses convert these positions to distances assuming a background cosmology. This approach thus requires doing the full data analysis for each background cosmological model one wants to test. Instead we propose to select galaxies in radial shells, according to their redshifts, and then measure and analyse the angular (2D) correlations in each bin circumventing the model assumption. Remarkably, we find that if we include in the analysis also the angular cross-correlations between different shells, we can recover the radial modes corresponding to the separations between radial bins. We extend this analysis to photometric galaxy surveys, such as Physics of the Accelerating Universe (PAU) and Dark Energy Survey (DES). Angular analysis in redshift bins is then the natural framework for such surveys. We show that we can obtain competitive constraints on the growth history of the Universe at high redshifts (z~1). Finally, we built galaxy survey mocks from the MICE simulations, including non-linear gravitational effects and observational ones such as redshift-space distortions and photo-z errors.  We found a good agreement between theory and simulation measurements. In the future, we expect to apply this framework for cosmological parameter estimation, especially focusing on DES and PAU surveys.

Gamma-ray emission of young stellar objects and discovery of superorbital variability at high energies

Estat: defended (30/07/2013)
Estudiant: Daniela Hadasch
Supervisat per: Diego F. Torres ; Font, Ll. (UAB)
Universitat: Universitat Autònoma de Barcelona

UAB Abstract - Department of Physics - Doctor of Physics   Gamma-ray emission of young stellar objects and discovery of super orbital variability at high energies   by Daniela Hadasch   This thesis is structured in three parts: 1.) Observations of binary systems with the Fermi…
Estat: defended (30/07/2013)
Estudiant: Daniela Hadasch
Supervisat per: Diego F. Torres ; Font, Ll. (UAB)
Universitat: Universitat Autònoma de Barcelona

UAB Abstract - Department of Physics - Doctor of Physics   Gamma-ray emission of young stellar objects and discovery of super orbital variability at high energies   by Daniela Hadasch   This thesis is structured in three parts: 1.) Observations of binary systems with the Fermi satellite and first discovery of superorbital modulation at high energies in the system LS I +61 ◦303, 2.) Studies of magnetars at high and at very high energies and deriving first upper limits on their γ-ray emission and 3.) Studies of the prospects forobservations of binary systems with the forthcoming Cherenkov Telescope Array.

GNSS-R as a Source of Opportunity for Remote Sensing of the Cryosphere

Estat: defended (13/05/2013)
Estudiant: Fran Fabra Cervellera
Supervisat per: Estel Cardellach Galí
Universitat: Universitat Politècnica de Catalunya

This work evaluates the potential use of signals from the Global Navigation Satellite Systems (GNSS) that scatter off the Earth surface for the retrieval of geophysical information from the cryosphere. For this purpose, the present study is based on data collected with a dedicated reflectometry GNSS…
Estat: defended (13/05/2013)
Estudiant: Fran Fabra Cervellera
Supervisat per: Estel Cardellach Galí
Universitat: Universitat Politècnica de Catalunya

This work evaluates the potential use of signals from the Global Navigation Satellite Systems (GNSS) that scatter off the Earth surface for the retrieval of geophysical information from the cryosphere. For this purpose, the present study is based on data collected with a dedicated reflectometry GNSS receiver during two field campaigns, which were focused on two types of characteristic surfaces of the cryosphere: thin sea ice covers and thick dry snow accumulations. During the first experiment, the complete process of formation, evolution and melting of sea ice was monitorized for more than seven months in a bay located in Greenland. This type of ice is typically characterized by its thickness, concentration and roughness. Different observables from GNSS reflections are analyzed to try to infer these properties. The ice thickness is linked to the free-board level, defined as the height of the sea ice
surface. Accurate phase altimetry is achieved, showing good agreement with an Arctic tide model. In addition, the long term results of ellipsoidal height retrievals are consistent with the evolution of the ice surface temperature product given by MODIS, which is a key parameter in the rate of growth of sea ice. On the other hand, the presence of salinity in the sea ice modifies its dielectric properties, resulting in different amplitude and phase for the co- and cross-polar components of the complex Fresnel coefficients. The polarimetric measurements obtained show good agreement with visual inspections of ice concentration from an Arctic weather station. Finally, the shape of the reflected signals and its phase dispersion are tested as potential signatures of surface roughness. For comparison, ice charts of the experimental area are employed. In particular, maximums in roughness given by the GNSS observables coincide with fast ice events. Fast ice is defined as ice anchored to the coast, where the tidal movements contribute to the development of strange patterns, cracks, and fissures on its surface, thus consistent with the GNSS-R roughness retrievals. The second experiment took place on Antarctica, monitoring a pristine snow area which is well-known for the calibration of remote sensing instruments. Due to the relative stability of the snow layers, the data acquisition was limited to ten continuous days. Interferometric beats were found after a first analysis of the amplitude from the collected signals, which were consistent with a multipath model where the reflector lies below the surface level. Motivated by these results, a forward model is developed that reconstructs the complex received signal as a sum of a finite number of reflections, coming from different snow layers (a snow density profile obtained from in-situ measurements). The interferometric information is then retrieved from the spectral analysis applied to time series from both real and modeled signals (lag-holograms). We find that the frequency bands predicted by the model are in general consistent with the data and the lag-holograms show repeatability for different days. Then, we attempt a proper inversion of the collected data to determine the dominant layers of the dry snow profile that contribute to L-band reflections, which are related to significant gradients of snow density/permittivity.

A search for low-mass objects in young star-forming regions

Estat: defended (12/04/2013)
Estudiant: Manuel Perger
Supervisat per: Martín, E.; Barrado y Navascues, D.

The best tool to characterize the formation of stars is the mass function. The members of the young and nearby Taurus star-forming region represent an important exception to the universal form of the function since many low-mass objects would be missing in this low-density region in order to match its…
Estat: defended (12/04/2013)
Estudiant: Manuel Perger
Supervisat per: Martín, E.; Barrado y Navascues, D.

The best tool to characterize the formation of stars is the mass function. The members of the young and nearby Taurus star-forming region represent an important exception to the universal form of the function since many low-mass objects would be missing in this low-density region in order to match its universal form.
We aimed to find new members of Taurus. To this end, we investigated the area located 5 deg north of the main clouds. To probe the link between the difference of the mass function of Taurus and its low density, we also studied the Orion region. As database for our search we used the wide-field near-infrared photometric survey UKIDSS GCS.  Additionally, we analyzed the photometric characteristics of all 351 already known Taurus members. All in all, we applied around 40 selection criteria. To prove the membership of all selected sources, we observed the candidates with low-resolution optical spectroscopy. In those wavelength ranges, many line features can reveal the youth of a source. To compare them, a set of already known Taurus members and field dwarfs were observed.
In Taurus and Orion, we observed 47 of 272 and 7 of 55 candidates, respectively. The complete photometric and spectral analysis revealed 7 and 4 of them as possible new WTTS members. The new Taurus members are not connected to any molecular cloud and have moved from their birth site to their present location. Their existence indicates a significant unknown population of Taurus members away from the main clouds. We conclude that the missing Taurus low-mass objects are located away from the main clouds of the region. The answer to whether this young and nearby star-forming region is unique or not can be found in its outer parts. The region is beyond doubt of lower density and more stretched out as previously assumed.

Populating cosmological simulations with galaxy using the HOD model

Estat: defended (01/02/2013)
Estudiant: Jorge Carretero Palacios
Supervisat per: Francisco Javier Castander Serentill; Enrique Gaztañaga
Universitat: Universitat Autònoma de Barcelona

We want to produce galaxy catalogs from N-body dark matter simulations. Those catalogs should be compare to real data and in this way we will learn about the process of galaxy formation.
Populating cosmological simulations with galaxy using the HOD model
Estat: defended (01/02/2013)
Estudiant: Jorge Carretero Palacios
Supervisat per: Francisco Javier Castander Serentill; Enrique Gaztañaga
Universitat: Universitat Autònoma de Barcelona

Populating cosmological simulations with galaxy using the HOD model

The role of magnetic fields in the formation of low and high mass stars

Estat: defended (12/06/2012)
Estudiant: Frau, P.
Supervisat per: Josep Miquel Girart Medina; Beltrán, M. T.
Universitat: Universitat de Barcelona

The complex interplay among self-gravity, thermal support, turbulence, rotation, and magnetic fields, and ultimately the observable features that arise from them, are not well characterized observationally and, therefore, not well understood theoretically. The fact that the starless cores are diffuse and cold objects, makes them very difficult of observing because their emission is very faint. Our goal in this work is to deepen into the understanding of the formation, survival and evolution of low-mass dense cores. We doubly face this objective since we aim: Firstly, to characterize observationally the physical and chemical properties of magnetized starless dense cores in the earliest stages of evolution to derive the initial conditions for star-formation, and to check whether the magnetic field is playing a role in the evolution of the cores and; Secondly, to compare observations of more evolved Class 0 sources with models of collapse of magnetized clouds to find the most likely initial conditions and dominant physical processes. In order to achieve the first goal, we have selected a sample of starless cores of the Pipe Nebula. This nearby dark molecular cloud complex has a very low star formation efficiency, which makes it an ideal target to study the properties and evolution of pristine starless dense cores. For the second goal, we have selected NGC 1333 IRAS 4A. It is probably the best studied low-mass protostellar dense core, not only through molecular and dust emission, but also through high angular resolution polarimetric observations of the dust emission.
The complex interplay among self-gravity, thermal support, turbulence, rotation, and magnetic fields, and ultimately the observable features that arise from them, are not well characterized observationally and, therefore, not well understood theoretically. The fact that the starless cores are diffuse…
Estat: defended (12/06/2012)
Estudiant: Frau, P.
Supervisat per: Josep Miquel Girart Medina; Beltrán, M. T.
Universitat: Universitat de Barcelona

The complex interplay among self-gravity, thermal support, turbulence, rotation, and magnetic fields, and ultimately the observable features that arise from them, are not well characterized observationally and, therefore, not well understood theoretically. The fact that the starless cores are diffuse and cold objects, makes them very difficult of observing because their emission is very faint. Our goal in this work is to deepen into the understanding of the formation, survival and evolution of low-mass dense cores. We doubly face this objective since we aim: Firstly, to characterize observationally the physical and chemical properties of magnetized starless dense cores in the earliest stages of evolution to derive the initial conditions for star-formation, and to check whether the magnetic field is playing a role in the evolution of the cores and; Secondly, to compare observations of more evolved Class 0 sources with models of collapse of magnetized clouds to find the most likely initial conditions and dominant physical processes. In order to achieve the first goal, we have selected a sample of starless cores of the Pipe Nebula. This nearby dark molecular cloud complex has a very low star formation efficiency, which makes it an ideal target to study the properties and evolution of pristine starless dense cores. For the second goal, we have selected NGC 1333 IRAS 4A. It is probably the best studied low-mass protostellar dense core, not only through molecular and dust emission, but also through high angular resolution polarimetric observations of the dust emission.

Star formation ahead of the Herbig-Haro 80N

Estat: defended (23/03/2012)
Estudiant: Masqué, J. M.
Supervisat per: Josep Miquel Girart Medina; Estalella, R.
Universitat: Universitat de Barcelona

This thesis is focused in the detailed study of the star formation process found ahead of the Herbig-Haro 80N
This thesis aims at probing the influence of protostellar outflows to nearby star forming cores by studying the particular case of the HH 80N core. To do so, we first study the chemical properties of the core in the frame of HH photoillumination. The HH 80N core is larger and more massive than other HH…
Estat: defended (23/03/2012)
Estudiant: Masqué, J. M.
Supervisat per: Josep Miquel Girart Medina; Estalella, R.
Universitat: Universitat de Barcelona

This thesis aims at probing the influence of protostellar outflows to nearby star forming cores by studying the particular case of the HH 80N core. To do so, we first study the chemical properties of the core in the frame of HH photoillumination. The HH 80N core is larger and more massive than other HH irradiated clumps, and harbors an embedded object, suggesting a different nature for this core. Our first goal is to see if the HH 80N core has a chemistry similar to that observed in other clumps ahead of HH objects. In the following step, we study the physical properties of the HH 80N core in order to look for evidence of the influence of the HH 80/81/80N jet in the star formation process that is taking place in this core. While many studies on triggered star formation are based on the statistics of a large number of objects \citep[e.g.][]{chauhan2011}, in this thesis we focus our study on an isolated star-forming core to find direct evidence of interaction of the HH 80/81/80N outflow with the core.

Focal plane detectors of a Laue lens telescope for Nuclear Astrophysics

Estat: defended (31/01/2012)
Estudiant: José Manuel Álvarez Pastor
Supervisat per: Margarita Hernanz Carbó
Universitat: Universitat Autònoma de Barcelona

TBW
Estat: defended (31/01/2012)
Estudiant: José Manuel Álvarez Pastor
Supervisat per: Margarita Hernanz Carbó
Universitat: Universitat Autònoma de Barcelona

TBW

Parallel Post-Processing Solution for GNSS-R Instrument

Estat: defended (16/12/2011)
Estudiant: Guo Yi
Supervisat per: Antonio Rius Jordán; Ferrer Ramis, Carles
Universitat: Universitat Autònoma de Barcelona

Microelectronica i Sistemes Electrònics
Estat: defended (16/12/2011)
Estudiant: Guo Yi
Supervisat per: Antonio Rius Jordán; Ferrer Ramis, Carles
Universitat: Universitat Autònoma de Barcelona

Microelectronica i Sistemes Electrònics

The Joan Oró Telescope at the Montsec Astronomical Observatory Solutions for Unattended Operation

Estat: defended (10/11/2011)
Estudiant: Josep Colomé Ferrer
Supervisat per: Ignasi Ribas Canudas
Universitat: Universitat de Barcelona

El objetivo principal de esta Tesis ha sido la robotización del Telescopio Joan Oró del Observatorio Astronómico del Montsec (TJO-OAdM) para conseguir un sistema con un alto nivel de autonomía y eficiencia. El telescopio robótico TJO-OAdM fue propuesto a mediados de los años 90 y representaba en…
Estat: defended (10/11/2011)
Estudiant: Josep Colomé Ferrer
Supervisat per: Ignasi Ribas Canudas
Universitat: Universitat de Barcelona

El objetivo principal de esta Tesis ha sido la robotización del Telescopio Joan Oró del Observatorio Astronómico del Montsec (TJO-OAdM) para conseguir un sistema con un alto nivel de autonomía y eficiencia. El telescopio robótico TJO-OAdM fue propuesto a mediados de los años 90 y representaba en ese momento un reto tecnológico para el campo de la instrumentación astronómica. Se concibió como un telescopio multipropósito con una operación completamente desatendida. El desarrollo inicial no cumplió con las expectativas de funcionamiento. Tenía varias deficiencias causadas principalmente por un desarrollo basado en una instrumentación comercial que no era adecuada para un control desatendido y fiable. Y, además, presentaba una incompleta definición de la arquitectura del sistema para garantizar el control de toda la instalación y de todos los procesos incluidos en el flujo de datos. El trabajo de la Tesis se ha focalizado en aplicar los cambios necesarios en el diseño inicial para tener un sistema capaz de dar respuestas inteligentes a cualquier situación así como proporcionar un control desatendido del flujo completo de datos. Las especificaciones incluyen desde la preparación e introducción en el sistema de las propuestas de observación hasta el procesado de los datos y la posterior entrega a los usuarios. El aislamiento del lugar y las condiciones meteorológicas extremas añaden un requerimiento de robustez al desarrollo del sistema. Se considera fundamental, pues, lograr una alta fiabilidad, robustez y calidad de los datos recogidos para maximizar la eficiencia y el retorno científico. La Tesis se estructura en tres bloques principales: el análisis y diseño del sistema, en el que se definen las necesidades y la estructura de control; la fase de desarrollo, en la que se presentan el diseño y la implementación de los módulos hardware y software que forman parte de la arquitectura de control; y el control de calidad, donde se ha realizado un análisis de riesgo y se han aplicado metodologías de verificación y validación para garantizar que el sistema final cumplía con los requerimientos iniciales.
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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
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