Homogeneous measurements of proximity zone sizes for 59 quasars in the Epoch of Reionization

The overionized regions surrounding high-redshift quasars, known as proximity zones, provide a window into the interaction between supermassive black holes (SMBHs) and the intergalactic medium (IGM) during the epoch of reionization (EoR). We present new homogeneous measurements of proximity zone sizes (Rₚ) for a sample of $59$ quasars spanning redshifts 5.77 ≤ z ≤ 7.54 (median $z = 6.59$). For $15$ of these sources, we measure Rₚ for the first time. The quasars in our catalog have absolute magnitudes at rest-frame $1450$ {A} in the range -29.13 ≤ M₁₄₅₀ ≤ -25.20 (median M₁₄₅₀ -26.49), providing one of the most extensive data sets for exploring Rₚ at these epochs. The distribution of Rₚ values shows a large scatter at fixed redshift and luminosity, likely reflecting variations in quasar lifetimes (tQ), IGM density fluctuations, and IGM neutral fraction. We fit a bivariate power-law model to a large sample of $100$ objects to study the dependence of Rₚ with both M₁₄₅₀ and z: we find that the evolution of Rₚ with luminosity is in agreement with the models (Rₚ ∝ 10^-0.4 M₁₄₅₀/2.87), while the evolution of Rₚ with z is steeper than previous works (Rₚ ∝ (1+z)-2.44). We identify $13$ quasars with small proximity zone size, defined using the residuals of our fit. In all cases, except for J2211$-$6320, we rule out the presence of associated dense absorbers that prematurely truncate Rₚ, and suggest a short tQ (10⁴ yr) as a possible explanation for their small proximity zone sizes.