We present the first far infrared (FIR) dust emission polarization map covering the full extent of Milky Way’s central molecular zone (CMZ). The data, obtained with the PILOT balloon-borne ...experiment, covers the Galactic center region − 2° < ℓ < 2°, − 4° < b < 3° at a wavelength of 240 μm and an angular resolution of 2.2′. From our measured dust polarization angles, we infer a magnetic field orientation projected onto the plane of the sky (POS) that is remarkably ordered over the full extent of the CMZ, with an average tilt angle of ≃22° clockwise with respect to the Galactic plane. Our results confirm previous claims that the field traced by dust polarized emission is oriented nearly orthogonally to the field traced by GHz radio synchrotron emission in the Galactic center region. The observed field structure is globally compatible with the latest Planck polarization data at 353 and 217 GHz. Upon subtraction of the extended emission in our data, the mean field orientation that we obtain shows good agreement with the mean field orientation measured at higher angular resolution by the JCMT within the 20 and 50 km s−1 molecular clouds. We find no evidence that the magnetic field orientation is related to the 100 pc twisted ring structure within the CMZ. The low polarization fraction in the Galactic center region measured with Planck at 353 GHz combined with a highly ordered projected field orientation is unusual. This feature actually extends to the whole inner Galactic plane. We propose that it could be caused by the increased number of turbulent cells for the long lines of sight towards the inner Galactic plane or to dust properties specific to the inner regions of the Galaxy. Assuming equipartition between magnetic pressure and ram pressure, we obtain magnetic field strength estimates of the order of 1 mG for several CMZ molecular clouds.
PILOT is a balloon-borne experiment designed to perform large-scale surveys of the polarized interstellar emission in the submillimeter. It is based on the use of an off-axis Gregorian type ...telescope, with a 1 m diameter primary mirror, and a large focal plane equipped with detectors arrays providing a
field of view. All optical elements except the primary mirror are located inside a large liquid He cryostat, cooled down to 3 K. Strong constraints are then imposed on the alignment between the primary mirror and the cold optics. The characterization and optimization of the optical system performances are critical to the success of the mission. In this paper, we present the modelling and measurements performed on the primary mirror for this purpose. The optical and mechanical parameters of the as-built primary mirror have been determined using a method based on 3D measurements of the mirror surface. The deformations expected under flight conditions due to temperature variations and flexion under gravity have been estimated. We have also performed measurements using a submillimeter test bench in order to control the image quality and derive the main optical parameters. The parameters derived from the modeling using 3D measurements are in agreement with the requirements except for the conic constant. The best positioning of the mirror has been optimized consequently. The modeling has also allowed us to determine the pre-flight alignment parameters of the mirror as a function of the expected structure temperature at ceiling altitude. We have shown that this adjustment will enable to keep the tight requirements on the focus position (
600 μm) within a range of
C around the ceiling temperature value. The submillimeter measurements have validated the results derived from the 3D measurement based modeling. The image quality was investigated by performing a spatial exploration in azimuth and elevation around the nominal focus position, and along the optical axis. The deviation between the predicted and measured positions of the best focus are 80 μm and 11″ in translation along the optical axis and in rotation respectively. The best image pattern is also close to the nominal one, with a sphericity deviation lower than 2 μm RMS. These results will be used for the end-to-end tests of the integrated instrument, and for the optimization of the alignment before flight.
EUSO-BALLOON has been conceived as a pathfinder for JEM-EUSO, a mission concept for a space-borne wide-field telescope monitoring the Earth’s nighttime atmosphere with the objective of recording the ...ultraviolet light from tracks initiated by ultra-high energy cosmic rays. Through a series of stratospheric balloon flights performed by the French Space Agency CNES, EUSO-BALLOON will serve as a test-bench for the key technologies of JEM-EUSO. EUSO-BALLOON shall perform an end-to-end test of all subsystems and components, and prove the global detection chain while improving our knowledge of the atmospheric and terrestrial ultraviolet background. The balloon-instrument also has the potential to detect for the first time UV-light generated by atmospheric air-shower from above, marking a milestone in the development of UHECR science, and paving the way for any future large scale, space-based ultra-high energy cosmic ray observatory.
Abstract
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. The Japan Aerospace Exploration Agency (JAXA) selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with an expected launch in the late 2020s using JAXA’s H3 rocket. LiteBIRD is planned to orbit the Sun–Earth Lagrangian point L2, where it will map the cosmic microwave background polarization over the entire sky for three years, with three telescopes in 15 frequency bands between 34 and 448 GHz, to achieve an unprecedented total sensitivity of $2.2\, \mu$K-arcmin, with a typical angular resolution of 0.5○ at 100 GHz. The primary scientific objective of LiteBIRD is to 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 insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. We provide an overview of the LiteBIRD project, including scientific objectives, mission and system requirements, operation concept, spacecraft and payload module design, expected scientific outcomes, potential design extensions, and synergies with other projects.
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