Abstract 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 Åin 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 (R 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.
Onorato et al. (Wed,) studied this question.