2017A&A...604A..23N

The radio-quiet quasar Q2059-360 at redshift z=3.08 is known to be close to a small Lyman α blob (LAB) and to be absorbed by a proximate damped Lyα (PDLA) system. Here, we present the Multi Unit Spectroscopic Explorer (MUSE) integral field spectroscopy follow-up of this quasi-stellar object (QSO). Our primary goal is to characterize this LAB in detail by mapping it both spatially and spectrally using the Lyα line, and by looking for high-ionization lines to constrain the emission mechanism. Combining the high sensitivity of the MUSE integral field spectrograph mounted on the Yepun telescope at ESO-VLT with the natural coronagraph provided by the PDLA, we map the LAB down to the QSO position, after robust subtraction of QSO light in the spectral domain. In addition to confirming earlier results for the small bright component of the LAB, we unveil a faint filamentary emission protruding to the south over about 80 pkpc (physical kpc); this results in a total size of about 120 pkpc. We derive the velocity field of the LAB (assuming no transfer effects) and map the Lyα line width. Upper limits are set to the flux of the NV λ1238-1242, CIV λ1548-1551, HeII λ1640, and CIII] λ1548-1551 lines. We have discovered two probable Lyα emitters at the same redshift as the LAB and at projected distances of 265kpc and 207kpc from the QSO; their Lyα luminosities might well be enhanced by the QSO radiation. We also find an emission line galaxy at z=0.33 near the line of sight to the QSO. This LAB shares the same general characteristics as the 17 others surrounding radio-quiet QSOs presented previously. However, there are indications that it may be centered on the PDLA galaxy rather than on the QSO.