Searching for Islands of Reionization: A Potential Ionized Bubble Powered by a Spectroscopic Overdensity at z = 8.7
Abstract
We present the results from a spectroscopic survey using the MOSFIRE near-infrared spectrograph on the 10m Keck telescope to search for Lyα emission from candidate galaxies at z ~9-10 in four of the CANDELS fields (GOODS-N, EGS, UDS, and COSMOS). We observed 11 target galaxies, detecting Lyα from one object in ~8.1 hours of integration, at z = 8.665 +/- 0.001 with an integrated signal-to-noise > 7. This galaxy is in the CANDELS Extended Groth Strip (EGS) field, and lies physically close (3.5 physical Mpc [pMpc]) to another confirmed galaxy in this field with Lyα detected at z=8.683 (Zitrin et al. 2015). The detection of Lyα suggests the existence of large (~1 pMpc) ionized bubbles fairly early in the reionization process. We explore the ionizing output needed to create bubbles of this size at this epoch and find that such a bubble requires more than the ionizing power provided by the full expected population of galaxies (by integrating the UV Luminosity Function down to MUV = -13). The Lyα we detect would be able to escape the predominantly-neutral intergalactic medium at this epoch if our galaxy is inhabiting an overdensity, which would be consistent with the photometric overdensity previously identified in this region by Finkelstein et al. 2021. This implies that the CANDELS EGS field is hosting an overdensity at z = 8.7 which is powering one (or more) ionized bubbles, a hypothesis that will be imminently testable with forthcoming James Webb Space Telescope observations in this field.
Turn this paper into a full lesson
ArcXiv compiles a staged curriculum from this paper: 8-12 lessons across beginner → advanced, synthesised section guides, visuals, flashcards, a quiz, exercises, and on-demand deep dives per section. Grounded in the abstract, never invented.