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 MOSFIRE near-infrared spectrograph on 10 m Keck telescope to search for Ly α emission candidate galaxies at z ∼ 9–10 in four of CANDELS fields (GOODS-N, EGS, UDS, and COSMOS). observed 11 target galaxies, detecting one object ∼8.1 hr integration, = 8.665 ± 0.001 with an integrated signal-to-noise ratio > 7. This galaxy is Extended Groth Strip (EGS) field lies physically close (3.5 physical Mpc [pMpc]) another confirmed this detected 8.683. The detection suggests existence large (∼1 pMpc) ionized bubbles fairly early reionization process. explore ionizing output needed create size epoch find that such bubble requires more than power provided by full expected population (by integrating UV luminosity function down M −13). we detect would be able escape predominantly neutral intergalactic medium if our inhabiting overdensity, which consistent photometric overdensity previously identified region Finkelstein et al. implies EGS hosting 8.7 powering or bubbles, hypothesis will imminently testable forthcoming James Webb Space Telescope observations field.