Understanding the Cosmological Evolution of Galaxies with Intensity Mapping

The intensity mapping (IM) technique has been devised as a powerful tool to investigate the large scale structure and galaxies, alternative and complementary to the more traditional means relying on galaxy detection. In the high-redshift universe, in particular, synergies of multiple IM tracers have been widely perceived as a promising way of revealing the connection between the emergence of first stars, galaxies and the reionization, a still mysterious chapter of cosmic history that even the JWST might not fully elucidate. I will present two main themes of my research on applications of the IM technique to understand the cosmological evolution of galaxies. On the experimental side, I will introduce the analysis and forecasting work I led for the Tomographic Ionized-carbon Mapping Experiment (TIME), a novel imaging spectrometer array recently commissioned that pioneers the quest for measuring large-scale intensity fluctuations of the 158-micron [CII] line emission redshifted from the epoch of reionization. On the theory side, I will introduce LIMFAST, a fast, semi-numerical simulation developed to physically and self-consistently simulate a large set of line-intensity mapping (LIM) data in different frequency regimes, including tracers of neutral gas (e.g., HI 21cm) and star-forming galaxies (e.g., Lyα, [CII]). I will elaborate on the scientific applications of LIMFAST to simulate multi-tracer LIM observations of high-redshift galaxies and their interplay with the intergalactic medium during reionization. In particular, I will describe how various LIM signals, such as Hα, Lyα and [CII], and their cross-correlations with the HI 21cm signal, may be affected by the astrophysics governing galaxy formation, such as feedback and star formation laws. I will also discuss how these astrophysical processes may be studied with future IM experiments and their synergy with other cosmological observations to deepen our understanding of high-redshift galaxy populations.