Continuum-subtracted line velocity-integrated maps of the quasars J2310+1855, J1148+5251, J0439+1634 (from top to bottom). Yellow crosses indicate the nominal coordinate of the source. The synthesized beam FWHM is reported at the bottom-left corners. The line maps are obtained by integrating over 1.2 × FWHM around the line central frequency. The black contours give the [ − 4, −2, 2, 3, 4, 5, 6, 7, 8, 16, 32]σ isophotes. Negative contours are shown as dotted lines.