Four HI clumps in the Leo ring where deep searches for the CO J = 1–0 and J = 2–1 lines have been carried out with the IRAM-30 m telescope (green circles). The circle size is the FWHM of the 115 GHz beam (22 arcsec). More than one location has been observed in Clump1 and Clump2E where Hα emission has been recently detected (see Figs. 2 and 3). The yellow contours indicate the column density of the HI gas in the giant Leo ring as observed with the VLA (45 arcsec beam) by Schneider et al. (1986). The magenta dashed circles indicate the location of the wobble OFF positions. The background image is the GALEX far-UV image.