Improving the Planck sky maps through Bayesian component separation

The Planck satellite has provided a multitude of data images of the full microwave sky, or sky maps, since it saw first light in 2009. Its observations of the Cosmic Microwave Background (CMB) data has been paramount in the estimation of cosmological parameters vital in many branches of physics and astronomy. Although the processing of this information is coming to an end, the data still exhibit significant systematic effects coupled with foreground contamination, which impairs our ability to determine these parameters accurately. In this thesis, we provide an overview of the Planck data analysis process with emphasis on Bayesian component separation methods for foreground removal. Furthermore, we seek to improve upon a new set of sky maps provided by Reijo Keskitalo at Lawrence Berkeley Laboratories. We do this by applying component separation in order to reveal systematic effects, which are subsequently corrected during map-making. This process is then repeated until systematic errors and foregrounds are suppressed to a satisfactory extent. Lastly, we present the results of our analysis with the application of the latest generation sky maps. These maps were produced as a result of the efforts described in this thesis. We conclude that the new sky maps exhibit a significant reduction in instrumental errors, in comparison to the current state-of-the-art

Closing the Loop: Joint Analysis of CMB Systematics and Foregrounds

The Cosmic Microwave Background (CMB) radiation is the oldest signal in the universe. It teaches us about the first moments after the universe came into existence, and thus informs us about its subsequent evolution. The CMB serves as the faint backdrop of the night sky, obscured by all the other astrophysical objects (primarily clouds of gas), which we call foregrounds. For precise measurements of the CMB, we require detailed characterization of these, and also of the observing instruments' systematics. Furthermore, the problems of foreground separation and instrument systematics are tightly interwoven. This thesis presents my work on disentangling this relationship. This is done by leveraging observations from several different experiments and simultaneous consideration of systematics and foregrounds in a “loop”-like manner. Through the application of these methods, my colleagues and I have created some of the cleanest maps of the sky in the microwave range, in the world. These maps in turn inform us about important properties of the universe

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