Cosmic infrared background​
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​The cosmic infrared background (CIB) is the dominant extragalactic emission at far-infrared to millimetre wavelengths. It is produced by the cumulative emission of dusty, star-forming galaxies across cosmic history, where starlight absorbed by interstellar dust is re-emitted in the infrared. The CIB thus traces the history of star formation, with most of its signal arising from galaxies at redshifts z ≃ 1–3, near the peak of cosmic star formation activity. On large angular scales, the CIB is correlated with the large-scale structure of the Universe and contributes significantly to the gravitational lensing of the CMB. These properties make it a powerful cosmological probe of dark matter and structure formation, complementing optical galaxy surveys. However, in frequency bands probed by CMB instruments like Planck, the CIB is strongly degenerate with thermal dust emission from our own Galaxy, which follows a similar modified-blackbody spectral energy distribution (SED) but with far higher intensity. This spectral degeneracy makes accurate separation of the two signals a central challenge in exploiting CIB observations for cosmology.
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(Click on paper's title to access the corresponding publication)
Planck Collaboration (corresponding author: Remazeilles; 150+ co-authors), A&A 596, A109 (2016)​​​​​​​​​​​
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In this Planck Collaboration paper, of which I am the lead author, we implemented a novel approach to disentangle the CIB from Galactic dust emission in Planck data, addressing the long-standing challenge of separating these two components over the entire sky. To overcome the spectral degeneracy between CIB and thermal dust, we applied the GNILC component separation method (Remazeilles et al., MNRAS 2011), which leverages spatial and statistical information (power spectra) where spectral information (SED) alone is degenerate. This approach enabled us to disentangle Galactic thermal dust emission from extragalactic dust (CIB) in the Planck observations. As a result, we produced new full-sky maps of the temperature and spectral index of Galactic dust with significantly reduced CIB contamination, while also releasing clean CIB maps over a large portion of the sky, offering a novel tracer of dark matter. The Planck GNILC CIB maps remain among the best templates for CMB "delensing", i.e., correcting for the gravitational lensing of the CMB (e.g., Yu et al., PRD 2017; Planck 2018 results. VIII, A&A 2020). All GNILC maps of Galactic dust and CIB have been publicly released by the Planck collaboration via the Planck Legacy Archive, and one was even featured on the front cover of A&A journal (volume 596).
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