Radio Astronomical Probes of Cosmic Reionization andthe First Luminous Sources: Probing the 'Twilight Zone'

摘要

The epoch of reionization (EoR) corresponds to a 'cosmic phase transition',when the neutral intergalactic medium (IGM) becomes ionized by the first starsand/or AGN. While the discoveries of Gunn-Peterson (GP) absorption troughsin the spectra of the highest redshift QSOs and large scale polarization of theCMB have set the first hard constraints on the EoR, the redshift and processof reionization, and the nature of the first luminous objects, remain two ofthe paramount questions in cosmic structure formation. Moreover, the GP ef-fect is such that observations of objects during this epoch will be difficult atwavelengths shorter than about 1 micron. Hence, cosmic reionization, and theformation of the first luminous objects, occurs in a 'twilight zone', observableonly at radio through near-IR wavelengths. In this talk I explore studies of theEoR at meter through sub-millimeter wavelengths. I present recent observationsof the dust, molecular gas, and star formation activity in the host galaxies ofthe highest redshift QSOs. These results have interesting implications on thetimescale for metal and dust enrichment, on the possibility of coeval formationof super massive black holes (SMBHs) and galaxies, and on the process of reion-ization. I then discuss future capabilities of low frequency radio astronomy tostudy the neutral IGM via the HI 121 cm line, including imaging and power spec-tral analyses of large scale structure in emission, and absorption studies towardthe first radio loud sources. I conclude with a summary of the VLA-VHF systemto study cosmic Stromgren spheres associated with the highest redshift SDSSQSOs in the H I 21 cm line at 190 MHz.