Time: 12:00 pm – 1:00 pm
Location: via Zoom
Speaker: Jason Sun (CalTech)
Title: Understanding the Cosmological Evolution of Galaxies with Intensity Mapping
Abstract:
The intensity mapping (IM) technique has been devised as a powerful tool to investigate the formation/evolution of 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 and 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). TIME is 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, which serves an ideal probe of ongoing cosmic star formation that sources the hydrogen-ionizing radiation background. I will discuss how TIME, with an optimization of survey strategy, can inform us about the reionization on its own and through synergies with other probes like galaxy surveys. I will also discuss challenges and opportunities arising from low-redshift “line interlopers”, namely rotational CO lines at z ≈ 0.5 to 2 for TIME, which require some exquisite cleaning strategy to be removed but at the same time allow a census of the molecular gas content of galaxies near the “cosmic high noon”. On the theory side, I will introduce LIMFAST, a fast, semi-numerical simulation developed to physically and self-consistently simulate a large set of high-redshift 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. Particular emphases will be on (1) 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; and (2) how these astrophysical processes may be studied with future LIM experiments to deepen our understanding of high-redshift galaxy populations from both observational and theoretical perspectives.