This paper reports the discovery of spatially-extended line-emitting nebula , reaching to \approx 100 physical kpc ( pkpc ) from a damped { Ly } \alpha absorber ( DLA ) at z _ { DLA } = 0.313 along the sightline toward QSO PKS 1127 - 145 ( z _ { QSO } = 1.188 ) .
This DLA was known to be associated with a galaxy group of dynamical mass M _ { group } \sim 3 \times 10 ^ { 12 } { M } _ { \odot } , but its physical origin remained ambiguous .
New wide-field integral field observations revealed a giant nebula detected in [ O II ] , H \beta , [ O III ] , H \alpha , and [ N II ] emission , with the line-emitting gas following closely the motions of group galaxies .
One of the denser streams passes directly in front of the QSO with kinematics consistent with the absorption profiles recorded in the QSO echelle spectra .
The emission morphology , kinematics , and line ratios of the nebula suggest that shocks and turbulent mixing layers , produced as a result of stripped gaseous streams moving at supersonic speed across the ambient hot medium , contribute significantly to the ionization of the gas .
While the DLA may not be associated with any specific detected member of the group , both the kinematic and dust properties are consistent with the DLA originating in streams of gas stripped from sub- L _ { * } group members at \lesssim 25 pkpc from the QSO sightline .
This study demonstrates that gas stripping in low-mass galaxy groups is effective in releasing metal-enriched gas from star-forming regions , producing absorption systems in QSO spectra , and that combining absorption and emission-line observations provides an exciting new opportunity for studying gas and galaxy co-evolution .