COLA1 [OIII] emitter sample

This implies that it resides in a highly ionized bubble and that it is leaking ionizing photons with a high escape fraction of f_esc_(LyC)=20-50%, making it a prime laboratory to study Lyman continuum escape in the Epoch of Reionization. COLA1 shows all the signs of a prolific ionizer with a Ly{alpha} escape fraction of 81+/-5%, Balmer decrement indicating no dust, a steep UV slope ({beta}_UV_=-3.2+/-0.4), and a star-formation surface density >~10x that of typical galaxies at similar redshift.

We detect five galaxies in COLA1's close environment ({DELTA}z<0.02). Exploiting the high spectroscopic completeness inherent to grism surveys, and using mock simulations that fully mimic the selection function, we show that the number of detected companions is very typical for a normal similarly UV-bright (M_UV_~-21.3) galaxy - that is, the ionized bubble around COLA1 is unlikely to be due to an excessively large over-density.

Instead, the measured ionizing properties suggest that COLA1 by itself might be powering the bubble required to explain its double-peaked Ly{alpha} profile (Rion~0.7pMpc), with only minor contributions from detected neighbors (-19.5<~M_UV_<~-17.5).