Finalized PhD theses

Number of entries: 82

Cosmology with Galaxy Clustering

Status: defended (11/06/2015)
Student: Kai Hoffmann
Supervised by: Enrique Gaztañaga
University: Universitat Autònoma de Barcelona

One of the fundamental goals of Cosmology is to understand how the Universe evolved from initial density fluctuations to the large-scale structure of galaxies which is observed today as the cosmic web. Cosmological models can predict the properties of this structure for a given decomposition of the universal energy into matter and the acceleration of the cosmic expansion. While the major part of matter is believed to consist of an unknown and invisible type of particles, the observed galaxies are assumed to be biased tracers of the total matter distribution. A detailed understanding of galaxy bias is necessary for constraining cosmological models by comparing their predictions to observations. In this thesis galaxy bias will be studied using observational and simulated data. As a first step different methods for measuring the bias will be investigated. For this purpose the bias will be derived from the MICE Simulation and the Millennium Simulation using two- and three-point correlation functions. This results will be compared to direct determinations of the bias from the density contrast. The analysis will be performed for different scales, mass ranges and redshifts. Furthermore the three-point correlation function will be used to test the local model for bias. Deviations of the measurements from the local model predictions will be studied for different cluster shapes. As a second step the dependence of galaxy bias on galaxy properties such as spectral type, color, morphology, magnitude and spatial environment will be investigated. For this purpose mock galaxy catalogs will be used, including semi-analytic models that are imposed on the Millennium Simulation and halo occupation models from the MICE simulation. The properties of the mock galaxies will be compared to observational data such as PAU and SDSS. These studies will provide a base for further investigations of galaxy bias derived from weak lensing observables and redshift space distortions.
For constraining cosmological models via the growth of large-scale matter fluctuations it is important to understand how the observed galaxies trace the full matter density field. The relation between the density fields of matter and galaxies is often approximated by a second- order expansion of…
Status: defended (11/06/2015)
Student: Kai Hoffmann
Supervised by: Enrique Gaztañaga
University: Universitat Autònoma de Barcelona

For constraining cosmological models via the growth of large-scale matter fluctuations it is important to understand how the observed galaxies trace the full matter density field. The relation between the density fields of matter and galaxies is often approximated by a second- order expansion of a so-called bias function. The freedom of the parameters in the bias function weakens cosmological constraints from observations. In this thesis we study two methods for determining the bias parameters independently from the growth. Our analysis is based on the matter field from the large MICE Grand Challenge simulation. Haloes, identified in this simulation, are associated with galaxies. The first method is to measure the bias parameters directly from third-order statistics of the halo and matter distributions. The second method is to predict them from the abundance of haloes as a function of halo mass (hereafter referred to as mass function). Our bias estimations from third-order statistics are based on three-point auto- and cross- correlations of halo and matter density fields in three dimensional configuration space. Using three-point auto-correlations and a local quadratic bias model we find a ∼ 20% overestimation of the linear bias parameter with respect to the reference from two-point correlations. This deviation can originate from ignoring non-local and higher-order contributions to the bias function, as well as from systematics in the measurements. The effect of such inaccuracies in the bias estimations on growth measurements are comparable with errors in our measure- ments, coming from sampling variance and noise. We also present a new method for measuring the growth which does not require a model for the dark matter three-point correlation. Res- ults from both approaches are in good agreement with predictions. By combining three-point auto- and cross-correlations one can either measure the linear bias without being affected by quadratic (local or non-local) terms in the bias functions or one can isolate such terms and compare them to predictions. Our linear bias measurements from such combinations are in very good agreement with the reference linear bias. The comparison of the non-local contributions with predictions reveals a strong scale dependence of the measurements with significant deviations from the predictions, even at very large scales. Our second approach for obtaining the bias parameters are predictions derived from the mass function via the peak-background split approach. We find significant 5−10% deviations between these predictions and the reference from two-point clustering. These deviations can only partly be explained with systematics affecting the bias predictions, coming from the halo mass function binning, the mass function error estimation and the mass function parameterisation from which the bias predictions are derived. Studying the mass function we find unifying relations between different mass function parameterisation. Furthermore, we find that the standard Jack-Knife method overestimates the mass function error covariance in the low mass range. We explain these deviations and present a new improved covariance estimator.

Bayesian data analysis for LISA Pathfinder. Techniques applied to system identificaction experiments.

Status: defended (13/01/2015)
Student: Nikolaos Karnesis
Supervised by: Carlos Sopuerta ; Miquel Nofrarias Serra
University: Universitat Autònoma de Barcelona

LISA is a joint mission between the European Space Agency (ESA) and the US National Aeronautics and Space Administration (NASA) that will become the first space-based Gravitational-Wave (GW) detector. LISA is a constellation of three spacecrafts that will access GW signals at frequencies of 1mHz and below, around five orders of magnitude below the kHz band where Earth-based detectors, such as VIRGO and LIGO operate. LISA will open a new window to the observation of the Universe and is expected to provide revolutionary discoveries in the areas of Astrophysics, Cosmology, and Fundamental Physics. Due to the technological complexity of LISA, ESA approved a percursor mission, LISA PathFinder (LPF), to test the readiness of the main LISA technology. The scientific working principle of LISA is the detection of tiny relative displacements between pairs of proof masses in nominally geodesic motion, or free fall, induced by passing GWs. LPF consists in a single spacecraft hosting two proof masses in nominal free fall, whose motions are monitored by means of a Mach-Zender laser interferometer. LPF is expected to be launched around 2012 and its ultimate objective is to measure the noise in the proof masses motion, and to understand its physical origin. There are many sources of noise identified (thermal, magnetic, particles of cosmic origin, etc), and properly modelling them requires a careful planning of the measurement sequence, plus of course the use of suitable analysis tools to process the various data channels. The research work proposed for this PhD project consists of the following three points: 1. Development of Data Analysis Tools for the LTPDA software tool in order to perform the Data Analysis during the mission operations and also for the scientific parts that will be carried out by our Research Group. Also to participate in the Mock Data Analysis challenges organized by the LPF community. 2. To study how to develop a LISA noise model from the outcome of the LPF mission. 3. To develop Data Analysis Tools for LISA, which consists in the detection of GW signals and the estimation of the physical parameters of the associated sources. Also to participate in Mock Data Analysis challenges organized by the LISA scientific community (LISC).
The eLISA concept design consists of a constellation of three space-crafts forming a triangle in the sky. While in a sun centered orbit, it will constantly monitor the distance oscillations between the test bodies enclosed in the different space-crafts. Its principal goal, is to detect oscillations that…
Status: defended (13/01/2015)
Student: Nikolaos Karnesis
Supervised by: Carlos Sopuerta ; Miquel Nofrarias Serra
University: Universitat Autònoma de Barcelona

The eLISA concept design consists of a constellation of three space-crafts forming a triangle in the sky. While in a sun centered orbit, it will constantly monitor the distance oscillations between the test bodies enclosed in the different space-crafts. Its principal goal, is to detect oscillations that are caused by passing Gravitational-Waves. The technical complexity of this design was the reason for ESA and NASA to approve the LISA Pathfinder mission (LPF) which aims at testing all the key technologies for future Gravitational-Wave space observatories.
The LISA Technology Package (LTP) instrument onboard the LPF satellite, can be considered as one eLISA arm, squeezed from 1 million km to approximately 30 cm, and it aims to measure the differential acceleration between two test-bodies with unparalleled precision via a Mach-Zehnder interferometer. Among its objectives we have: The estimation of the acceleration noise models, the derivation of an accurate dynamical model of the system in all degrees-of-freedom, and the estimation of the systems’ parameters. In this thesis, we focus on a Bayesian analysis framework to set-up analysis strategies to process the planned system identification experiments.

We first model the system using different approximations, and then we develop and apply Markov Chain Monte Carlo (MCMC) algorithms to simulated data-sets. We report the accuracy on the parameters over the planned system identification experiments, that can be divided in two categories; the x-axis system identification experiments, that are performed over the sensitive axis defined by the line joining the two
test masses; and the so-called cross-talk experiments, where different degrees of freedom of the test bodies of the system are excited. The various cross-coupling physical effects that produce signal leakage on the sensitive differential interferometer channel,are then identified and estimated. In addition, the pipeline analysis designed for on-line
data analysis during operations is presented.

Finally, we also investigate the possible model selection problems in LPF data analysis, and we apply the reversible jump MCMC algorithm to simulated data sets. Different applications to the x-axis and the cross-talk experiments are considered, where the efficiency of the developed tools is demonstrated. We also show the association of
the model selection results to the design of the experiment itself. The above work is integrated to the LTP data analysis dedicated toolbox, the LTPDA. 

Stellar activity in exoplanet hosts

Status: defended (06/10/2014)
Student: Enrique Herrero Casas
Supervised by: Ignasi Ribas Canudas
University: Universitat de Barcelona

Stellar activity in exoplanet hosts Most of the efforts on the search and characterization of Earth-like exoplanets are currently focused on low mass stars. Some important properties related to the structure and processes in this type of stars are still unknown, so a careful characterization…
Status: defended (06/10/2014)
Student: Enrique Herrero Casas
Supervised by: Ignasi Ribas Canudas
University: Universitat de Barcelona

Stellar activity in exoplanet hosts Most of the efforts on the search and characterization of Earth-like exoplanets are currently focused on low mass stars. Some important properties related to the structure and processes in this type of stars are still unknown, so a careful characterization is essential as one of the next steps in exoplanet sciences. The characterization of stellar activity in low mass stars was carried out through several techniques that allowed us both to model and to simulate the relationships between the observational data and the stellar properties. Several empyrical relations for low mass stars allow to find correlations between certain activity indicators and the rotation period. These have permitted us to generate synthetic samples of stars with stochastic distributions of stellar and geometric properties allowing to estimate the inclination of the rotation axis from the distribution in the activity-vsini diagram. The methodology was applied to a sample of 1200 observed low mass stars and the best candidates for a targeted transit search were selected. Spot modelling techniques allow to obtain physical information about the stellar surface from time series photometric and spectroscopic data. In this work we analyse Kepler photometry of LHS 6343 A, an M-dwarf being eclipsed by a brown dwarf companion every 12.718 days, and showing photometric oscillations with the same periodicity and a phase lag of 100o from the eclipses. The accurate modeling of the Kepler data allowed to explain these oscillations with the presence of active regions appearing at a fixed longitude, thus suggesting a possible magnetic connection between both components. On the other hand, we also studied an alternative explanation for the photometric oscillations in LHS 6343 A in terms of the Doppler beaming effect, showing that this could be the main cause of the observed oscillations. Stellar activity effects are responsible for the noise observed at different amplitude and timescales on time series data. Such noise represents one of the main limitations for exoplanetary sciences. In order to characterize it, we designed a methodology to simulate the photosphere of an active rotating star through the integration of small surface elements from Phoenix atmosphere models. This allows to characterize the signal produced by activity and further study its relationship with the stellar properties, as well as the possible effects produced on exoplanet measurements. The methodology allowed us to present several strategies in order to correct or reduce the effects of spots on the photometry of exoplanet transits, as these may induce significant variations on the measurement of the planetary radius. We focused on a comprehensive analysis of HD 189733, a K5 star hosting a giant planet, which has simultaneous photometric (MOST) and spectroscopic (SOPHIE) data available. An accurate surface map was obtained using the methodology above, accurately reproducing the light curve and radial velocity observations. Such map was used in order to study the effects of activity on the exoplanet transits. We showed that the effects of spot-crossing events are significant even for mid-infrared wavelengths. Moreover, the chromatic effects of spots not occulted by the planet show a signal with a wavelength dependence and amplitude that are very similar to the signature of the atmosphere of a planet dom- inated by dust. The radial velocity theoretical curve is in agreement with the observations up to the typical instrumental systematics of SOPHIE. The results from this work conclude that it is essential to correctly model the stellar activity signals for exoplanetary sciences, and we provide some tools and strategies to characterize and reduce such effects and extract astrophysical information. 

Theory and observations of the PWN-SNR complex

Status: defended (21/07/2014)
Student: Jonatan Martín Rodríguez
Supervised by: Diego F. Torres ; Nanda Rea
University: Universitat Autònoma de Barcelona

In this work, we study theoretical and observational issues about pulsars (PSRs), pulsar wind nebulae (PWNe) and supernova remnants (SNRs). In particular, the spectral modeling of young PWNe and the X-ray analysis of SNRs with magnetars comparing their characteristics with those remnants surrounding…
Status: defended (21/07/2014)
Student: Jonatan Martín Rodríguez
Supervised by: Diego F. Torres ; Nanda Rea
University: Universitat Autònoma de Barcelona

In this work, we study theoretical and observational issues about pulsars (PSRs), pulsar wind nebulae (PWNe) and supernova remnants (SNRs). In particular, the spectral modeling of young PWNe and the X-ray analysis of SNRs with magnetars comparing their characteristics with those remnants surrounding canonical pulsars. The spectra of PWNe range from radio to $\gamma$-rays. They are the largest class of identified Galactic sources in $\gamma$-rays increasing the number from 1 to $\sim$30 during the last years. We have developed a detailed spectral code which reproduces the electromagnetic spectrum of PWNe in free expansion ($t_{age} \lesssim$10 kyr). We shed light and try to understand issues on time evolution of the spectra, the synchrotron self-Compton dominance in the Crab Nebula, the particle dominance in PWNe detected at TeV energies and how physical parameters constrain the detectability of PWNe at TeV. We make a systematic study of all Galactic, TeV-detected, young PWNe which allows to find correlations and trends between parameters. We also discuss about the spectrum of those PWNe not detected at TeV and if models with low magnetized nebulae can explain the lack of detection or, on the contrary, high-magnetization models are more favorable. Regarding the X-ray analysis of SNRs, we use X-ray spectroscopy in SNRs with magnetars to discuss about the formation mechanism of such extremely magnetized PSRs. The alpha-dynamo mechanism proposed in the 1990's produces an energy release that should have influence in the energy of the SN explosion. We extend the work done previously done by \cite{vink06} about the energetics of the SN explosion looking for this energy release and we look for the element ionization and the X-ray luminosity and we compare our results with other SNRs with an associated central source.

Weak Lensing Analysis of an All-Sky Simulation

Status: defended (24/01/2014)
Student: Carlos Lopez Arenillas
Supervised by: Pablo Fosalba Vela; Enrique Gaztañaga
University: Universitat de Barcelona

This Thesis is concerned with one of the most promising probes to constrain the "Dark Universe", and, particularly, the dark matter distribution. Based on MICE cosmological simulation, and the all-sky convergence maps generated by Fosalba, Gaztanaga, Castander & Manera (2003) we perform a mass calibration…
Status: defended (24/01/2014)
Student: Carlos Lopez Arenillas
Supervised by: Pablo Fosalba Vela; Enrique Gaztañaga
University: Universitat de Barcelona

This Thesis is concerned with one of the most promising probes to constrain the "Dark Universe", and, particularly, the dark matter distribution. Based on MICE cosmological simulation, and the all-sky convergence maps generated by Fosalba, Gaztanaga, Castander & Manera (2003) we perform a mass calibration of the dark matter halos there contained up to z=1. In order to do that, we analyse the average halo density proÖles of all the halos with masses ranging from 5E13 to 4E14 Msol/h , divided into four mass bins and three redshift bins. Through this analysis we address two main issues: the relatively low mass resolution of the simulation (mp=2.34 1011 h1M ) and the relatively high softening length (lsoft=50 h1 Kpc). We do that by using a two-step procedure. First, we simulate analytical pure NFW density profiles (with di§erent mass resolutions) using two input values: the virial radii of MICE halos and the expected concentrations, according to the Öxed mass-concentration relation from Oguri and Hamana [130]. Second, we model the e§ect of the softening length with a Gaussian Ölter, smoothing the halo core. The results show that MICE halos are, in average, NFW halos. Best-O NFW radii are in very good agreement with the average radii of our samples, overestimating the data by  1%, but best-fit NFW concentrations are in average 50% lower than the expected values. It is possible to account for part of this deviation by distinguishing between relaxed and unrelaxed halos, finding that, depending on the degree of relaxedness, the improvement can be as high as 30%. We also find that the analytical NFW halos simulated with MICE mass resolution have an overall concentration 40% lower than the input concentration, in the case of 3D proÖles, and 25% lower in that of the projected proÖles. The Gaussian-smoothed NFW profile is a good approximation for our projected halos. Additionally, we analyse the morphology of the halos, characterizing their triaxiality at R200 and calculating their orientation with respect to the line-of-sight (LOS). MICE halos tend to adopt a more prolate morphology, as might be expected from a  CDM simulation (Shaw et al. [159]), and the percentage of prolate halos grows as their mass grows. The mass resolution is, nonetheless, not good enough to draw conclusive inferences from the shape analysis, but it allows us to discern a trend and estimate the e§ect of halo shape and orientation on the weak lensing masses. Finally, we use the all-sky convergence maps to study the scatter in mass measurements of MICE halos. We determine the intrinsic scatter in the recovered masses by assuming the smoothed NFW profile as the ìtrueî profile, and creating two new convergence maps from different mass cuts. We estimate also the scatter due to the correlated structure by studying the angles between the major axes of the halos and the LOS, and also that due to projection e§ects (i.e. all the dark matter between observer and source). We find an irreducible scatter (intrinsic) of 10-14%, a scatter around a 30% of the intrinsic one due to correlated structure, and a scatter around 40-70% of the intrinsic one due to projection e§ects. The size of our halo sample allows us to improve the characterization of the cosmic noise, of great importance for present and future surveys.

CROSS-CORRELATING SPECTROSCOPIC AND PHOTOMETRIC GALAXY SURVEYS

Status: defended (16/01/2014)
Student: Martin B. Eriksen
Supervised by: Enrique Gaztañaga
University: Universitat Autònoma de Barcelona

CROSS-CORRELATING SPECTROSCOPIC AND PHOTOMETRIC GALAXY SURVEYS
Status: defended (16/01/2014)
Student: Martin B. Eriksen
Supervised by: Enrique Gaztañaga
University: Universitat Autònoma de Barcelona

CROSS-CORRELATING SPECTROSCOPIC AND PHOTOMETRIC GALAXY SURVEYS

Dynamically-generated baryon resonances with heavy flavor

Status: defended (10/01/2014)
Student: Romanets, O. (KVI, University of Groningen)
Supervised by: Tolos, L.; Timmermans, R. (KVI, University of Groningen)

To study the properties of exotic hadrons with charm and strange content under extreme conditions of density and temperature, with applications for astrophysical observables in neutron stars and supernovae as well as for the future FAIR project at GSI.
Study the properties of dynamically-generated baryon resonaces with strange and charm content
Status: defended (10/01/2014)
Student: Romanets, O. (KVI, University of Groningen)
Supervised by: Tolos, L.; Timmermans, R. (KVI, University of Groningen)

Study the properties of dynamically-generated baryon resonaces with strange and charm content

Theories of modified gravity and reconstruction schemes of cosmological models

Status: defended (08/11/2013)
Student: Antonio Jesús López Revelles
Supervised by: Emilio Elizalde ; Sergei D Odintsov
University: Universitat de Barcelona

The present thesis, aimed at obtaining the title of Philosophy Doctor in Physics, is based on the following papers published in referred journals, pre-prints and conference proceedings:  S. Capozziello, M. De Laurentis and A. J. Lopez-Revelles. Weak eld limit for F(R; G) modi ed gravities. In preparation. …
Status: defended (08/11/2013)
Student: Antonio Jesús López Revelles
Supervised by: Emilio Elizalde ; Sergei D Odintsov
University: Universitat de Barcelona

The present thesis, aimed at obtaining the title of Philosophy Doctor in Physics, is based on the
following papers published in referred journals, pre-prints and conference proceedings:
 S. Capozziello, M. De Laurentis and A. J. Lopez-Revelles. Weak eld limit for F(R; G) modi ed
gravities. In preparation.
 K. Bamba, A. J. Lopez-Revelles, R. Myrzakulov, S. D. Odintsov, and L. Sebastiani. Cosmic history
of viable exponential gravity: Equation of state oscillations and growth index from in
ation to dark
energy era. Class. Quant. Grav. 30:015008 (2013).
 K. Bamba, A. J. Lopez-Revelles, R. Myrzakulov, S. D. Odintsov, and L. Sebastiani. The universe
evolution in exponential F(R) -gravity. Proceedings of QFTG2013, published in TSPU Bulletin 3
(128), 2012, n 13 p.19-24.
 E. Elizalde and A. J. Lopez-Revelles.Reconstructing cosmic acceleration from modi ed and nonmin-
imal gravity: The Yang-Mills case. Phys. Rev. D, 82:063504 (2010).
 E. Elizalde, A. J. Lopez-Revelles, S. D. Odintsov, and S. Yu. Vernov. Cosmological models with
Yang-Mills elds. Phys.Atom.Nucl., 76:996 (2013).
 A. J. Lopez-Revelles. Growth of matter perturbations for realistic F(R) models. Phys. Rev. D,
87:024021 (2013).
 A. J. Lopez-Revelles. Reconstructing cosmic acceleration from f(R) modi ed gravity. Proceedings
of ERE2011, Madrid. ArXiv: 1301.2190.
 A. J. Lopez-Revelles and E. Elizalde. Universal procedure to cure future singularities of dark energy
models. Gen. Rel. Grav., 44:751 (2012).
 A. J. Lopez-Revelles, R. Myrzakulov and D. Saez-Gomez. Ekpyrotic universes in F(R) Horava-
Lifshitz gravity. Phys. Rev. D, 85:103521 (2012).

Measuring Large Scale Structure using angular cross-correlations

Status: defended (27/09/2013)
Student: Jacobo Asorey Barreiro
Supervised by: Enrique Gaztañaga ; Martin Crocce
University: 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…
Status: defended (27/09/2013)
Student: Jacobo Asorey Barreiro
Supervised by: Enrique Gaztañaga ; Martin Crocce
University: 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

Status: defended (30/07/2013)
Student: Daniela Hadasch
Supervised by: Diego F. Torres ; Font, Ll. (UAB)
University: 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…
Status: defended (30/07/2013)
Student: Daniela Hadasch
Supervised by: Diego F. Torres ; Font, Ll. (UAB)
University: 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.
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