Speaker
Description
During cosmic reionization, ionized regions gradually grew and overlapped in the IGM. Understanding when and how reionization happened is crucial for studying the early structure formation and the properties of first galaxies in the Universe. At z>5.5, the observed IGM optical depth shows a significant scatter, indicating an inhomogeneous reionization process. However, the nature of the inhomogeneous reionization, whether it is dominated by the large-scale fluctuations in the ionizing background or in the IGM temperature, remains unclear. ASPIRE is a JWST cycle 1 program that has spectroscopically identified more than 400 [OIII] emitters at z>5 in 25 quasar fields at z>6.5. These [OIII] emitters provide independent and sensitive tracers of large-scale galaxy density in 25 quasar fields. Combined with deep ground-based optical spectroscopy of 25 ASPIRE quasars, covering Lyman alpha forests from z~5.3 to z~6.3, ASPIRE program provides the current largest sample for IGM-galaxy connection studies during cosmic reionization. We present the preliminary relation between IGM optical depth and galaxy overdensities at z>5.5 using ASPIRE program. We will discuss their constraints on reionization models and implications on the inhomogeneity of reionization process.
