Three Lyα Emitting Galaxies within a Quasar Proximity Zone at z ∼ 5.8

Quasar proximity zones at z > 5.5 correspond to overdense and overionized environments. Galaxies found inside proximity zones can therefore display features that would otherwise be masked by absorption in the intergalactic medium. We demonstrate the utility of this quasar-galaxy synergy by reporting the discovery of the first three proximate Ly alpha emitters (LAEs) within the proximity zone of quasar J0836+0054 at z = 5.795 (Aerith A, B, and C). Aerith A, located behind the quasar with an impact parameter D-perpendicular to = 278. 8 pkpc, provides the first detection of an Ly alpha transverse proximity effect. We model the transmission and show that it constrains the onset of J0836's quasar phase to 0.2Myr < t < 28 Myr in the past. The second object, Aerith B at a distance D < 912 pkpc from the quasar, displays a bright and broad double-peaked Ly alpha emission line. The peak separation implies a low ionizing f(esc) less than or similar to 1%. We fit the Ly alpha line with an outflowing shell model, finding a typical central density log N-H I/cm(-2) = 19.3(-0.2)(+0.8), outflow velocity = v(out) = 16(-11)(+4) km s(-1), and gas temperature = log T/K 3.8(-0.7)(+0.8) compared to 2 < z < 3 analog LAEs. We detect object Aerith C via an Ly alpha emission line at z = 5.726. This corresponds with the edge of the quasar's proximity zone (Delta z < 0.02), suggesting that the proximity zone is truncated by a density fluctuation. Via the analyses conducted here, we illustrate how proximate LAEs offer unique insight into the ionizing properties of both quasars and galaxies during hydrogen reionization.