Lyα Halos around z ∼ 6 Quasars

Abstract

We present deep MUSE observations of five quasars within the first Gyr of the universe (z ≳ 6), four of which display extended Lyα halos. After PSF subtraction, we reveal halos surrounding two quasars for the first time, as well as confirm the presence of two more halos for which tentative detections exist in long-slit spectroscopic observations and narrowband imaging. The four Lyα halos presented here are diverse in morphology and size, they each display spatial asymmetry, and none are centered on the position of the quasar. Spectra of the diffuse halos demonstrate that none are dramatically offset in velocity from the systemic redshift of the quasars (∆v < 200 km s<SUP>-1</SUP>) however. each halo shows a broad Lyα line, with a velocity width ∼1000 km s<SUP>-1</SUP>. Total Lyα luminosities range between ∼2 × 10<SUP>43</SUP> and ∼2 × 10<SUP>44</SUP> erg s<SUP>-1</SUP>, reaching maximum radial extents of 13-30 pkpc from the quasar positions. We find larger sizes and higher Lyα luminosities than previous literature results at this redshift, but find no correlation between the quasar properties and the Lyα halo, suggesting that the detected emission is most closely related to the physical properties of the circumgalactic medium.