As a prevalent and widely distributed component of galactic gas, neutral atomic hydrogen (HI) and Carbon lines (CO, CII) play a crucial role in comprehending various astrophysical processes, including star formation histories, galaxy interactions, and the tracing of cosmic large-scale structures. However, the sensitivity limitations of telescopes pose challenges to directly measuring line signals from distant individual galaxies, particularly at low redshifts. This limitation can be overcome by employing HI/CII intensity mapping, thereby extending the survey capabilities to higher redshifts.
In this presentation, I will delineate our efforts in gaining scientific insights through various methodologies, specifically focusing on HI intensity mapping using the FAST (Five-hundred-meter Aperture Spherical radio Telescope) and CII intensity mapping through CONCERTO (CarbON CII line in post-rEionisation and ReionisaTiOn epoch). Firstly, I will present our projections for FAST, providing a comparative analysis with galaxy surveys. Subsequently, I will introduce our meticulously developed data-processing pipeline and shed light on how the presence of 1/f noise in real drift-scan data can impact the measurement of the HI power spectrum. Lastly, I will explore the advancements made in the CONCERTO project, which represents the inaugural endeavor to conduct a survey of [CII] line intensity mapping in the COSMOS field, specifically targeting redshifts exceeding 5.2. This presentation will highlight the project's efficacy in mapping continuums.