Dos aproximaciones a la cosmología observacional moderna: detección de fuentes puntuales en mapas de la polarización del fondo cósmico de microondas y estimación de la distribución de materia oscura en cúmulos de galaxias

ABSTRACT: In this work, two of the current researching fields in Modern Observational Cosmology are approached: the search for observational evidence of primordial gravitational waves, and the determination of the properties of dark matter. Firstly, a wavelet-based filter was designed to characterize the properties of the extragalactic point-like sources which threaten to obscure the signal left by primordial gravitational waves in the Cosmic Microwave Background. Tests of the filter performance in simulations of the microwave sky show the advantages of operating in E- and B-mode polarization maps, particularly in the B-mode, rather than in the maps of the conventional Stokes’ parameters Q and U, when working with point-like sources. Secondly, the basics behind Weak Gravitational Lensing techniques are also reviewed, applying them to map the projected mass density of the A2142 Abell galaxy cluster. The combination of maps of projected mass density, like the ones constructed here with the galaxies distribution seen on mergers of Galaxy clusters, could lead to new constrains on the physical properties of dark matter, like its self-interactions.RESUMEN: En este trabajo se tratan dos de las líneas de investigación que actualmente ocupan a la Cosmología Observacional Moderna: la búsqueda de pruebas observacionales de las ondas gravitacionales primigéneas y la determinación de las propiedades de la materia oscura. En relación al primer aspecto, se ha diseñado un filtro para caracterizar las propiedades de las fuentes puntuales extragalácticas, las cuales amenazan con ocultar la señal dejada por las ondas gravitacionales primigéneas en el Fondo Cósmico de Microondas. Las pruebas realizadas con el nuevo filtro usando simulaciones del cielo de microondas, demuestran las ventajas que a la hora de trabajar con fuentes puntuales implica operar en mapas de los modos E y B de polarización, especialmente en el modo B, en lugar de usar los convencionales mapas de los parámetros de Stokes Q y U. En lo que al segundo tema se refiere, se revisan los fundamentos detrás del efecto Lente Gravitacional Débil, aplicandolos al mapeado de la densidad de masa proyectada del cúmulo de galaxias A2142. Combinando mapas de densidad de masa proyectada como los aquí obtenidos, con la distribución de galaxias que puede observarse en colisiones de cúmulos galácticos, pueden acotarse propiedades físicas de la materia oscura, como su capacidad de auto-interacción.Grado en Físic

Estudio del deslensado del modo B de polarización del fondo cósmico de microondas : detectabilidad de las ondas gravitacionales primordiales

ABSTRACT: The most promising channel to detect the Primordial Gravitational Wave background, the smoking gun observable proving that an inflationary period took place, lies in the B-mode polarization of the Cosmic Microwave Background (CMB). However, due to its very low amplitude, the imprint it leaves on CMB polarization is vastly obscured by galactic microwave emissions and the B-mode polarization produced by weak gravitational lensing. As CMB experiments and component separation techniques are approaching the sensitivity at which lensed B-modes become the main obstacle in the detection of the primordial B-mode, we decided to study how well could the lensing effect be reversed for CMB maps with the noise levels that may be expected from future missions, and using high-quality reconstructions of the lensing potential. We found that lensing potential reconstructions must reach around a 500δ signal-to-noise ratio themselves to reduce the lensed B-mode spectrum to half its amplitude, conditions in which a 2δ detection of an r = 6 X 10-4 would be possible. For such reconstructions to be internally produced from the CMB, CMB maps must have an instrumental noise below the 1μK. arcmin level.RESUMEN: El modo B de polarización del Fondo Cósmico de Microondas (FCM) constituye el canal más prometedor para la detección del fondo de Ondas Gravitacionales Primordiales, el observable que indiscutiblemente probaría la existencia de un periodo inflacionario. Sin embargo, debido a su extremadamente baja amplitud, la huella que deja en la polarización del FCM queda oculta muy por debajo la emisión en microondas de nuestra galaxia y del modo B inducido por el efecto lente gravitacional débil. Ahora que los experimentos del FCM y las técnicas de separación de componentes se están acercando a la sensibilidad a la cual los modos B lensados empieza a ser el principal obstáculo en la detección del modo B primordial, hemos decidido estudiar cómo de bien sería posible revertir el efecto lente en mapas del FCM con los niveles de ruido que cabría esperar de futuras misiones y usando reconstrucciones del potencial de lensing de alta calidad. Hemos encontrado que las reconstrucciones del potencial de lensing deben alcanzar un ratio señal-ruido de 500δ para conseguir reducir a la mitad la amplitud del modo B lensado, condiciones en las que una detección a 2δ de r = 6X10-4 sería posible. Si tales reconstrucciones han de producirse internamente a partir del FCM, los mapas del FCM deben contar con un ruido instrumental por debajo del nivel del 1μK.arcmin.Máster en Física de Partículas y del Cosmo

Fundamental physics with the cosmic microwave background polarization

El fondo cósmico de microondas (FCM) ha desempeñado un papel fundamental en el establecimiento de ΛCDM como modelo cosmológico de concordancia. Las medidas de alta precisión de la polarización del FCM que están por desarrollarse en las próximas décadas nos ayudarán a abordar las cuestiones pendientes sobre la naturaleza de la materia oscura, la energía oscura y la inflación cósmica, así como a arrojar algo más de luz sobre las tensiones observacionales actuales. El éxito de este ambicioso programa científico no sólo supone un reto tecnológico, también exigirá un control sin precedentes de la sistemática, un modelado preciso del resto de emisiones galácticas y extragalácticas en el rango de las microondas, al igual que el desarrollo de nuevas herramientas de análisis. En la presente tesis se recopilan varias publicaciones que tratan diferentes aspectos de dicho procesado de datos como la separación de componentes, la mitigación de sistemáticas y la eliminación de anisotropías secundarias.The cosmic microwave background (CMB) has played a pivotal role in establishing ΛCDM as the concordance cosmological model. The next decades will see the advent of high-precision measurements of the CMB polarization that will help us address the outstanding questions on the nature of dark matter, dark energy, and cosmic inflation, as well as shed some more light on present observational tensions. The success of such an ambitious science program not only poses a technological challenge but will also demand unparalleled control of systematics, a precise understanding of Galactic and extragalactic foreground emissions, and the development of new analysis tools. This thesis compiles several publications covering various steps of such analysis pipeline, dealing with different aspects of component separation, the mitigation of systematics, and the removal of secondary anisotropies

In-flight polarization angle calibration for LiteBIRD: blind challenge and cosmological implications

International audienceWe present a demonstration of the in-flight polarization angle calibration for the JAXA/ISAS second strategic large class mission, LiteBIRD, and estimate its impact on the measurement of the tensor-to-scalar ratio parameter, r, using simulated data. We generate a set of simulated sky maps with CMB and polarized foreground emission, and inject instrumental noise and polarization angle offsets to the 22 (partially overlapping) LiteBIRD frequency channels. Our in-flight angle calibration relies on nulling the EB cross correlation of the polarized signal in each channel. This calibration step has been carried out by two independent groups with a blind analysis, allowing an accuracy of the order of a few arc-minutes to be reached on the estimate of the angle offsets. Both the corrected and uncorrected multi-frequency maps are propagated through the foreground cleaning step, with the goal of computing clean CMB maps. We employ two component separation algorithms, the Bayesian-Separation of Components and Residuals Estimate Tool (B-SeCRET), and the Needlet Internal Linear Combination (NILC). We find that the recovered CMB maps obtained with algorithms that do not make any assumptions about the foreground properties, such as NILC, are only mildly affected by the angle miscalibration. However, polarization angle offsets strongly bias results obtained with the parametric fitting method. Once the miscalibration angles are corrected by EB nulling prior to the component separation, both component separation algorithms result in an unbiased estimation of the r parameter. While this work is motivated by the conceptual design study for LiteBIRD, its framework can be broadly applied to any CMB polarization experiment. In particular, the combination of simulation plus blind analysis provides a robust forecast by taking into account not only detector sensitivity but also systematic effects

Concept design of low frequency telescope for CMB B-mode polarization satellite LiteBIRD

LiteBIRD has been selected as JAXA’s strategic large mission in the 2020s, to observe the cosmic microwave background (CMB) B-mode polarization over the full sky at large angular scales. The challenges of LiteBIRD are the wide field-of-view (FoV) and broadband capabilities of millimeter-wave polarization measurements, which are derived from the system requirements. The possible paths of stray light increase with a wider FoV and the far sidelobe knowledge of -56 dB is a challenging optical requirement. A crossed-Dragone configuration was chosen for the low frequency telescope (LFT : 34–161 GHz), one of LiteBIRD’s onboard telescopes. It has a wide field-of-view (18° x 9°) with an aperture of 400 mm in diameter, corresponding to an angular resolution of about 30 arcminutes around 100 GHz. The focal ratio f/3.0 and the crossing angle of the optical axes of 90◦ are chosen after an extensive study of the stray light. The primary and secondary reflectors have rectangular shapes with serrations to reduce the diffraction pattern from the edges of the mirrors. The reflectors and structure are made of aluminum to proportionally contract from warm down to the operating temperature at 5 K. A 1/4 scaled model of the LFT has been developed to validate the wide field-of-view design and to demonstrate the reduced far sidelobes. A polarization modulation unit (PMU), realized with a half-wave plate (HWP) is placed in front of the aperture stop, the entrance pupil of this system. A large focal plane with approximately 1000 AlMn TES detectors and frequency multiplexing SQUID amplifiers is cooled to 100 mK. The lens and sinuous antennas have broadband capability. Performance specifications of the LFT and an outline of the proposed verification plan are presented

Overview of the medium and high frequency telescopes of the LiteBIRD space mission

LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular scales, and over 15 frequency bands from 34 GHz to 448 GHz. The LiteBIRD instruments consist of three telescopes, namely the Low-, Medium-and High-Frequency Telescope (respectively LFT, MFT and HFT). We present in this paper an overview of the design of the Medium-Frequency Telescope (89{224 GHz) and the High-Frequency Telescope (166{448 GHz), the so-called MHFT, under European responsibility, which are two cryogenic refractive telescopes cooled down to 5 K. They include a continuous rotating half-wave plate as the first optical element, two high-density polyethylene (HDPE) lenses and more than three thousand transition-edge sensor (TES) detectors cooled to 100 mK. We provide an overview of the concept design and the remaining specific challenges that we have to face in order to achieve the scientific goals of LiteBIRD

LiteBIRD satellite: JAXA's new strategic L-class mission for all-sky surveys of cosmic microwave background polarization

LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. JAXA selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with its expected launch in the late 2020s using JAXA's H3 rocket. LiteBIRD plans to map the cosmic microwave background (CMB) polarization over the full sky with unprecedented precision. Its main scientific objective is to carry out a definitive search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with an insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. To this end, LiteBIRD will perform full-sky surveys for three years at the Sun-Earth Lagrangian point L2 for 15 frequency bands between 34 and 448 GHz with three telescopes, to achieve a total sensitivity of 2.16 μK-arcmin with a typical angular resolution of 0.5° at 100 GHz. We provide an overview of the LiteBIRD project, including scientific objectives, mission requirements, top-level system requirements, operation concept, and expected scientific outcomes