2021MNRAS.508.5612M

We present the first characterization of the circumgalactic medium of Ly α emitters (LAEs), using a sample of 96 z ≃ 3.3 LAEs detected with the VLT/MUSE in fields centred on eight bright background quasars. The LAEs have low Ly α luminosities (∼10⁴² erg s^–1) and star formation rates (SFRs) ∼1 M_☉yr^–1, which for main-sequence galaxies correspond to stellar masses of only ∼10^8.6 M_☉. The median transverse distance between the LAEs and the quasar sightlines is 165 proper kpc (pkpc). We stacked the high-resolution quasar spectra and measured significant excess H I and C IV absorption near the LAEs out to 500 km s^–1 and at least ≃250 pkpc (corresponding to ≃7 virial radii). At ≲30 km s^–1 from the galaxies, the median H I and C IV optical depths are enhanced by an order of magnitude. The absorption is significantly stronger around the ≃1/3 of our LAEs that are part of 'groups', which we attribute to the large-scale structures in which they are embedded. We do not detect any strong dependence of either the H I or C IV absorption on transverse distance (over the range ≃50-250 pkpc), redshift, or the properties of the Ly α emission line (luminosity, full width at half-maximum, or equivalent width). However, for H I, but not C IV, the absorption at ≲100 km s^–1 from the LAE does increase with the SFR. This suggests that LAEs surrounded by more H I tend to have higher SFRs.