Physics & Astronomy Colloquium: "Millimeter-wave spectroscopy as a probe of the high-redshift universe"

"Millimeter-wave spectroscopy as a probe of the high-redshift universe"

Dr. Oliver Jeong, Lawrence Berkeley National Laboratory
Thursday, October 8, 2026
12:45-2:00pm – HR 136 (coffee hour beginning at 12:15pm) 

Answering the open questions of cosmology, from the physics of inflation to the nature of dark energy, requires maps of ever-larger volumes of the Universe. Line intensity mapping (LIM) is an emerging technique built for this purpose, measuring the aggregate atomic and molecular line emission of unresolved sources to map vast cosmic volumes. I will introduce LIM through the far-infrared lines of carbon monoxide (CO) and ionized carbon ([CII]), which are bright and unobscured by dust, and therefore reach unexplored epochs of cosmic history. Yet just how bright they are at high redshift remains poorly known, with predictions differing by an order of magnitude or more. I will present an empirical model of how CO and [CII] luminosity traces halo mass, calibrated against the full collection of existing measurements and new brightness-temperature detections, which sharpens these predictions and sets realistic sensitivity targets for future experiments.  I will then present the superconducting on-chip spectrometer we have developed to detect these faint high-redshift signals, whose per-channel efficiency breaks the fifty-percent ceiling of existing designs, and outline the path from this device to survey instruments for next-generation cosmological observatories.

Oliver Jeong is a postdoctoral scholar at Lawrence Berkeley National Laboratory and the CNRS-UC Berkeley International Research Laboratory, where he leads the Berkeley Line Intensity Mapping group. He received his AB in Physics from Princeton University and his PhD in Physics from UC Berkeley, for work on the optics of the Simons Array cosmic microwave background telescopes. He then served as an instrument scientist for the project, leading field deployments in the Chilean Atacama and a search for axion-like particles through observations of the Crab Nebula. His current work centers on superconducting on-chip spectrometers for millimeter-wave cosmology and on establishing line intensity mapping as the next-generation probe of large-scale structure at high redshift. He is also the dark-matter search lead for LuSEE-Night, a radio-frequency experiment bound for the far side of the Moon.