Line intensity mapping at mm/sub-mm wavelengths: developing a new probe of cosmology

Line Intensity Mapping (LIM) is a promising observational technique with applications spanning many areas of cosmology and astrophysics. The spatial distribution and measured redshift specific emission lines serve as a tracer of the underlying of the distribution of matter that allows us to build 3D maps of large-scale structure throughout the history of the Universe. There exists a wide range of spectral emission lines that fall within the mm/sub-mm wavelength range, providing multiple independent tracers that allow us probe structure across a redshift range out to the epoch of reionisation. The Astronomy Instrumentation Group (AIG) at Cardiff has a long-standing reputation in the development of long-wavelength instrumentation and we are now playing leading roles in a number of key experiments, including the Simon's Observatory (SO) and the South Pole Telescope (SPT). This project provides an opportunity to develop new experimental approaches that are needed to realise LIM at mm wavelengths, as well as lead analysis of new and recent on-sky datasets taken with the SPT.

The experimental aspect of this project will focus on the development of a new class of superconducting on-chip mm-wave spectrometers that will be optimised for the next generation of LIM surveys. The small size, natural scalability, and intrinsic detector sensitivity are all well matched to the needs of future mm-wave LIM experiments. The AIG is a world leader in the development of superconducting detector technologies and mm-wave instrumentation, and this project leverages the broad range of AIG facilities and capabilities including; low-temperature cryogenic test equipment, mm/sub-mm quasi-optical components, and a new state-of-the-art nanofabrication centre through the AIG's role within the Institute for Compound Semiconductors.

Cardiff is involved in the design, construction, and deployment of the SPT Summertime Line Intensity Mapper (SPT-SLIM), a pathfinder experiment dedicated to demonstrating the suitability of on-chip spectrometer technology for LIM. Scheduled to deploy in late 2023, SPT-SLIM will observe during the austral summer and is expected to provide a new and rich dataset. Throughout the duration of this Ph.D. project, the successful candidate will have opportunities to undertake important roles in the development and testing of the analysis and data reduction pipeline, a critical step toward establishing mm-wave LIM as a new cosmological observable.