{"id":111,"date":"2025-07-14T16:32:53","date_gmt":"2025-07-14T20:32:53","guid":{"rendered":"https:\/\/sites.bu.edu\/karkarelab\/?page_id=111"},"modified":"2025-07-14T16:35:41","modified_gmt":"2025-07-14T20:35:41","slug":"lim","status":"publish","type":"page","link":"https:\/\/sites.bu.edu\/karkarelab\/lim\/","title":{"rendered":"Line Intensity Mapping"},"content":{"rendered":"<p>Until now, we have learned about cosmology primarily from the CMB (beginning of the universe) and from supernovae and galaxy surveys (late-time universe). To completely understand cosmological physics and the properties of the first stars and galaxies, we want to map the universe <em>across its entire history.<\/em> But there is a problem: using standard techniques, galaxies in the early universe are too faint to be detected in large quantities.<\/p>\n<p>We are developing a new technique, called <strong>line intensity mapping (LIM)<\/strong>, to efficiently measure large-scale structure in the early universe. There are two ingredients:<\/p>\n<ul>\n<li>Instead of resolving galaxies, use moderate-resolution observations to integrate over multiple emitters. While we don&#8217;t learn about individual objects, this method is more efficient at detecting <em>cosmic structure in aggregate<\/em> when the emitters are extremely faint.<\/li>\n<li>Identify an atomic or molecular line emitted by galaxies in the early universe. If we know the rest-frame wavelength, the observed wavelength provides the <em>redshift<\/em>, or distance away from us, and we can construct a 3D map of cosmic structure.<\/li>\n<\/ul>\n<p>We focus on LIM at millimeter wavelengths, which is sensitive to far-infrared lines (in the galaxy rest frame) that are bright in distant galaxies, and which we can detect using instruments similar to those we build for the CMB. Our projections show that mm-wave LIM could provide an order of magnitude more cosmological constraining power than current galaxy surveys, testing the physics of dark energy, dark matter, neutrinos, and inflation to unprecedented precision.<\/p>\n<hr \/>\n<p>In 2021 our group started the <strong>SPT-SLIM<\/strong> (South Pole Telescope Shirokoff Line Intensity Mapper) project. SPT-SLIM is pioneering LIM measurements using <em>on-chip mm-wave spectrometers, <\/em>a new detector technology that dramatically improves sensitivity over traditional methods.\u00a0 We deployed our pathfinder instrument the South Pole Telescope for first-season observations in January 2025. Specific projects include:<\/p>\n<ul>\n<li>Spectrometer testing and bandpass characterization<\/li>\n<li>Analysis of on-sky data to constrain the power spectrum of high-redshift galaxies<\/li>\n<li>Forecasting to understand the science reach of LIM measurements<\/li>\n<\/ul>\n<div id='gallery-1' class='gallery galleryid-111 gallery-columns-2 gallery-size-responsive_gallery'><figure class='gallery-item'>\n\t\t\t<div class='gallery-icon portrait'>\n\t\t\t\t<a href='\/karkarelab\/files\/2025\/07\/slim_cryolift.jpg'><img width=\"550\" height=\"550\" src=\"\/karkarelab\/files\/2025\/07\/slim_cryolift-550x550.jpg\" class=\"attachment-responsive_gallery size-responsive_gallery\" alt=\"\" loading=\"lazy\" aria-describedby=\"gallery-1-122\" srcset=\"https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_cryolift-550x550.jpg 550w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_cryolift-150x150.jpg 150w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_cryolift-710x710.jpg 710w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_cryolift-300x300.jpg 300w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_cryolift-600x600.jpg 600w\" sizes=\"(max-width: 550px) 100vw, 550px\" \/><\/a>\n\t\t\t<\/div>\n\t\t\t\t<figcaption class='wp-caption-text gallery-caption' id='gallery-1-122'>\n\t\t\t\tLifting the SPT-SLIM cryostat\n\t\t\t\t<\/figcaption><\/figure><figure class='gallery-item'>\n\t\t\t<div class='gallery-icon portrait'>\n\t\t\t\t<a href='\/karkarelab\/files\/2025\/07\/slim_electronics.jpeg'><img width=\"550\" height=\"550\" src=\"\/karkarelab\/files\/2025\/07\/slim_electronics-550x550.jpeg\" class=\"attachment-responsive_gallery size-responsive_gallery\" alt=\"\" loading=\"lazy\" aria-describedby=\"gallery-1-121\" srcset=\"https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_electronics-550x550.jpeg 550w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_electronics-150x150.jpeg 150w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_electronics-710x710.jpeg 710w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_electronics-300x300.jpeg 300w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_electronics-600x600.jpeg 600w\" sizes=\"(max-width: 550px) 100vw, 550px\" \/><\/a>\n\t\t\t<\/div>\n\t\t\t\t<figcaption class='wp-caption-text gallery-caption' id='gallery-1-121'>\n\t\t\t\tThe SPT-SLIM electronics package\n\t\t\t\t<\/figcaption><\/figure><figure class='gallery-item'>\n\t\t\t<div class='gallery-icon portrait'>\n\t\t\t\t<a href='\/karkarelab\/files\/2025\/07\/slim_mirror_shop.jpeg'><img width=\"550\" height=\"550\" src=\"\/karkarelab\/files\/2025\/07\/slim_mirror_shop-550x550.jpeg\" class=\"attachment-responsive_gallery size-responsive_gallery\" alt=\"\" loading=\"lazy\" aria-describedby=\"gallery-1-124\" srcset=\"https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_mirror_shop-550x550.jpeg 550w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_mirror_shop-150x150.jpeg 150w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_mirror_shop-710x710.jpeg 710w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_mirror_shop-300x300.jpeg 300w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_mirror_shop-600x600.jpeg 600w\" sizes=\"(max-width: 550px) 100vw, 550px\" \/><\/a>\n\t\t\t<\/div>\n\t\t\t\t<figcaption class='wp-caption-text gallery-caption' id='gallery-1-124'>\n\t\t\t\tSecondary mirror mid-fabrication at BU\n\t\t\t\t<\/figcaption><\/figure><figure class='gallery-item'>\n\t\t\t<div class='gallery-icon landscape'>\n\t\t\t\t<a href='\/karkarelab\/files\/2025\/07\/slim_spt.jpg'><img width=\"550\" height=\"550\" src=\"\/karkarelab\/files\/2025\/07\/slim_spt-550x550.jpg\" class=\"attachment-responsive_gallery size-responsive_gallery\" alt=\"\" loading=\"lazy\" aria-describedby=\"gallery-1-123\" srcset=\"https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_spt-550x550.jpg 550w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_spt-150x150.jpg 150w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_spt-300x300.jpg 300w, https:\/\/sites.bu.edu\/karkarelab\/files\/2025\/07\/slim_spt-600x600.jpg 600w\" sizes=\"(max-width: 550px) 100vw, 550px\" \/><\/a>\n\t\t\t<\/div>\n\t\t\t\t<figcaption class='wp-caption-text gallery-caption' id='gallery-1-123'>\n\t\t\t\tOur team at South Pole, January 2025\n\t\t\t\t<\/figcaption><\/figure>\n\t\t<\/div>\n\n<hr \/>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Until now, we have learned about cosmology primarily from the CMB (beginning of the universe) and from supernovae and galaxy surveys (late-time universe). To completely understand cosmological physics and the properties of the first stars and galaxies, we want to map the universe across its entire history. But there is a problem: using standard techniques, [&hellip;]<\/p>\n","protected":false},"author":24451,"featured_media":0,"parent":0,"menu_order":3,"comment_status":"closed","ping_status":"closed","template":"","meta":[],"_links":{"self":[{"href":"https:\/\/sites.bu.edu\/karkarelab\/wp-json\/wp\/v2\/pages\/111"}],"collection":[{"href":"https:\/\/sites.bu.edu\/karkarelab\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sites.bu.edu\/karkarelab\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sites.bu.edu\/karkarelab\/wp-json\/wp\/v2\/users\/24451"}],"replies":[{"embeddable":true,"href":"https:\/\/sites.bu.edu\/karkarelab\/wp-json\/wp\/v2\/comments?post=111"}],"version-history":[{"count":9,"href":"https:\/\/sites.bu.edu\/karkarelab\/wp-json\/wp\/v2\/pages\/111\/revisions"}],"predecessor-version":[{"id":127,"href":"https:\/\/sites.bu.edu\/karkarelab\/wp-json\/wp\/v2\/pages\/111\/revisions\/127"}],"wp:attachment":[{"href":"https:\/\/sites.bu.edu\/karkarelab\/wp-json\/wp\/v2\/media?parent=111"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}