Mid-Term Report Summary - MISTIC (Mastering the dusty and magnetized Interstellar Screen to Test Inflation Cosmology)
How did the Universe begin? The prevailing idea is that the Bang of the Big Bang was an early burst of exponential expansion, dubbed inflation. A key prediction of inflation is that it generated gravitational waves. The corresponding ripples in the space-time fabric left an imprint in the polarisation of the Cosmic Microwave Background (CMB). Experiments are making a major step towards this signal by mapping the microwave sky polarisation with an unprecedented sensitivity and combination of sky coverage, angular resolution and wavelengths. These experiments may show whether the energy scale of inflation predicted by the simplest models is correct. However, unlike for temperature anisotropies, Galactic foregrounds have larger amplitude than any putative primordial B-mode signal. The signature of cosmic inflation will not be detected, unless contamination associated with the dusty and magnetized interstellar medium in the Galaxy is removed with the required accuracy and confidence. Within the competitive field of CMB studies, the MISTIC project proposes a unique contribution to the search for its B-mode polarisation. The MISTIC team has the unmatched ambition and capability to tie the analysis of polarisation data and component separation to state-of-the-art understanding and modelling of the dusty magnetized interstellar medium. Our goal is to achieve the breakthroughs in the fields of Galactic astrophysics, microwave sky modelling, and component separation, required to achieve the best sensitivity on the B-mode CMB polarisation. Our work bridges data analysis, physical modelling, sky modelling and component separation into an iterative process that will take full advantage of the uniqueness and complementarities of expertise and data gathered in the MISTIC project, in particular our access to the Planck survey data.
The Planck satellite has completed the first whole sky map of dust polarization. The data is revealing a new sky that the MISTIC team had the privilege to explore. The observations have the sensitivity to image dust polarization over the whole sky. For the first time, we have the data needed to characterize the structure of the turbulent component of the Galactic magnetic field in the diffuse interstellar medium, molecular clouds and star forming regions. Our analysis of the data also involves the characterization of the polarization properties of dust. From this perspective, we seek to answer two main questions. Which grains contribute to the observed polarization? Where in the interstellar medium, and with what efficiency, are they aligned with the Galactic magnetic field?
The MISTIC team, within the Planck consortium, is playing a leading role in the analysis of the Planck polarization data, in particular in the preparation of the publications on dust polarization. These publications, combined with earlier publications on emission components, are novel and significant steps forward in identifying and disentangling the imprints of the interstellar matter and the Galactic magnetic field structure on one hand, and of dust properties on the other hand, which are encoded in the sky images and in the frequency dependence of Galactic emission and polarization. The MISTIC team is working towards characterizing the intricate structure of the magnetic field introduced by its coupling to interstellar turbulence. This part of our research aims at revealing the role the magnetic field plays in the formation of the filamentary structure of interstellar matter. Our research is also opening a new perspective on interstellar dust by providing first measurements of the millimetre emission of Galactic dust, and evidence for evolution of the emission and polarization properties of dust in the diffuse interstellar medium. This work in setting new standards on dust which challenge existing models in deep ways.
The MISTIC project is also successful in establishing a significant interface between the astrophysics of the sky polarization and cosmology, in particular the search for B-mode CMB polarization. We have quantified the separation problem between Galactic and CMB polarization. Our work is also contributing a detailed understanding of the frequency dependence of Galactic emission and polarization, which is key to component separation. To reach the full data sensitivity of Planck to CMB polarization at low l multipoles, the power of dust polarization at 143 GHz needs to be separated from that of the CMB to an accuracy of a few %. This is a challenge still ahead of us, which also involves correction of calibration differences between CMB and dust emission that introduce leakage from emission to polarization. The MISTIC team will be a key actor in the final steps of the data analysis where the required reduction of data systematics will come from the combination of data calibration, sky modelling and component separation.
The Planck satellite has completed the first whole sky map of dust polarization. The data is revealing a new sky that the MISTIC team had the privilege to explore. The observations have the sensitivity to image dust polarization over the whole sky. For the first time, we have the data needed to characterize the structure of the turbulent component of the Galactic magnetic field in the diffuse interstellar medium, molecular clouds and star forming regions. Our analysis of the data also involves the characterization of the polarization properties of dust. From this perspective, we seek to answer two main questions. Which grains contribute to the observed polarization? Where in the interstellar medium, and with what efficiency, are they aligned with the Galactic magnetic field?
The MISTIC team, within the Planck consortium, is playing a leading role in the analysis of the Planck polarization data, in particular in the preparation of the publications on dust polarization. These publications, combined with earlier publications on emission components, are novel and significant steps forward in identifying and disentangling the imprints of the interstellar matter and the Galactic magnetic field structure on one hand, and of dust properties on the other hand, which are encoded in the sky images and in the frequency dependence of Galactic emission and polarization. The MISTIC team is working towards characterizing the intricate structure of the magnetic field introduced by its coupling to interstellar turbulence. This part of our research aims at revealing the role the magnetic field plays in the formation of the filamentary structure of interstellar matter. Our research is also opening a new perspective on interstellar dust by providing first measurements of the millimetre emission of Galactic dust, and evidence for evolution of the emission and polarization properties of dust in the diffuse interstellar medium. This work in setting new standards on dust which challenge existing models in deep ways.
The MISTIC project is also successful in establishing a significant interface between the astrophysics of the sky polarization and cosmology, in particular the search for B-mode CMB polarization. We have quantified the separation problem between Galactic and CMB polarization. Our work is also contributing a detailed understanding of the frequency dependence of Galactic emission and polarization, which is key to component separation. To reach the full data sensitivity of Planck to CMB polarization at low l multipoles, the power of dust polarization at 143 GHz needs to be separated from that of the CMB to an accuracy of a few %. This is a challenge still ahead of us, which also involves correction of calibration differences between CMB and dust emission that introduce leakage from emission to polarization. The MISTIC team will be a key actor in the final steps of the data analysis where the required reduction of data systematics will come from the combination of data calibration, sky modelling and component separation.