Cosmology and Astrophysics with Intensity Mapping

Citation

Cheng, Yun-Ting (2022) Cosmology and Astrophysics with Intensity Mapping. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/p41n-8698. https://resolver.caltech.edu/CaltechTHESIS:07122021-033018615

Abstract

Intensity mapping (IM) has emerged as a promising technique to probe the largescale structures and galaxy formation and evolution across cosmic history. As IM measures the aggregate emission from all sources, it can overcome the limitation of conventional detection-based observations, where the emission from diffuse populations and high-redshift faint galaxies cannot be resolved individually. As several IM experiments will come online in the next decade, demand for IM modeling and data analysis strategies has increased. In this thesis, we present a range of analysis techniques, theoretical modeling, and data analysis results related to IM.

In Chapter 2, we aim to answer the question: When should we use IM? We present a formalism to describe both IM and galaxy detection (GD) approaches, and use it to quantify their individual performance when measuring the large-scale structure (LSS). With this formalism, we can identify the scenarios where each approach is advantageous. We also develop a simple metric for determining the optimal strategy to map the LSS with future experiments.

In Chapters 3 and 4, we interrogate methods for improving the line intensity mapping (LIM) analysis. LIM traces the three-dimensional structure of the universe by probing the emission field from a spectral line. One particular challenge for LIM is to separate the target line signals from interloper lines along the line of sight in order to extract the desired cosmological and astrophysical information. Previously proposed methods of line de-blending, such as masking and cross-correlation, rely on the external galaxy tracers, but sometimes a galaxy catalog with sufficient depth and sky coverage does not exist. Therefore, we develop two new methods for performing line de-confusion that do not require any external information. The first method (Chapter 3) uses the distinct shape of large-scale two-dimensional power spectra of signals and interlopers to distinguish the line emission from different redshifts. The second method (Chapter 4) reconstructs the intensity maps of individual lines from LIM data in the phase space, using multiple lines from the same source to identify the source redshift. We show that both of our methods are able to effectively extract desired line signals from the upcoming LIM experiments.

In Chapter 5, we discuss the application of IM for studying the extragalactic background light (EBL), the integrated light from all sources of emission in the universe. Previous studies on the fluctuations of the EBL indicate that the intra-halo light (IHL) has a significant contribution to the near-infrared EBL. Chapter 5 presents the results on probing the IHL using a stacking analysis of images from the Cosmic Infrared Background Experiment (CIBER). CIBER is a rocket-borne experiment designed to image and perform photometry of the near-infrared EBL. Our results suggest that at z ∼ 0.3 the IHL comprises a large fraction of light associated with ∼ L_∗ galaxies, implying that the IHL accounts for a non-negligible fraction of the near-infrared cosmic radiation budget.

In Chapter 6, we present a forecast on the EBL constraints with the upcoming SPHEREx mission. We consider cross correlating SPHEREx intensity maps with galaxy catalogs from several current and future surveys. Our model predicts that the EBL spectrum as a function of redshift can be detected from the local universe to the epoch of reionization.

The analysis techniques developed in this thesis can help better extract the information from the IM data; the future IM experiments will extend our current works on investigating the EBL. Therefore, the research in this thesis provides important toolkits and foundations for upcoming IM experiments.

Thesis Files