Suppression of Low-mass Galaxy Formation around Quasars at z ∼ 2–3

Abstract

We have carried out deep and wide field imaging observations with narrow bands, targeting 11 quasar fields to systematically study the possible photoevaporation effect of quasar radiation on surrounding low mass galaxies at z  ∼ 2–3. We focused on Ly α emitters (LAEs) at the same redshifts as quasars that lie within the quasar proximity zones, where the UV radiation from the quasars is higher than the average background at that epoch. We found that LAEs with high rest-frame equivalent width of Ly α emission (EW 0 ) of ≳150 Å with low stellar mass (≲10 8 M ⊙ ) are predominantly scarce in the quasar proximity zones, suggesting that quasar photoevaporation effects may be taking place. The halo mass of LAEs with EW 0  > 150 Å is estimated to be either from spectral energy distribution fitting or the main sequence. Based on a hydrodynamical simulation, the predicted delay in star formation under a local UV background intensity with erg s −1 cm −2 Hz −1 sr −1 for galaxies having less than this halo mass is about >20 Myr, which is longer than the expected age of LAEs with EW 0  > 150 Å. On the other hand, photoevaporation seems to be less effective around very luminous quasars, which is consistent with the idea that these are still in an early stage of activity.