WISDOM project XX -- Strong shear tearing molecular clouds apart in NGC 524

Early-type galaxies (ETGs) are known to harbour dense spheroids of stars but scarce star formation (SF). Approximately a quarter of these galaxies have rich molecular gas reservoirs yet do not form stars efficiently. We study here the ETG NGC~524, with strong shear suspected to result in a smooth molecular gas disc and low star-formation efficiency (SFE). We present new spatially-resolved observations of the 12CO (2-1) -emitting cold molecular gas from the Atacama Large Millimeter/sub-millimeter Array (ALMA) and of the warm ionised-gas emission lines from SITELLE at the Canada-France-Hawaii Telescope. Although constrained by the resolution of the ALMA observations (37~pc), we identify only 52 GMCs with radii ranging from 30 to 140~pc, a low mean molecular gas mass surface density ₆₀ₒ125~M_~pc^-2 and a high mean virial parameter ₎₁ₒ, ₕ₈ₑ5. 3. We measure spatially-resolved molecular gas depletion times (₃₄₏1/ SFE) with a spatial resolution of 100~pc within a galactocentric distance of 1. 5~kpc. The global depletion time is 2. 0~Gyr but ₃₄₏ increases toward the galaxy centre, with a maximum ₃₄₏, ₌₀ₗ5. 2~Gyr. However, no pure HII region is identified in NGC~524 using ionised-gas emission-line ratio diagnostics, so the ₃₄₏ inferred are in fact lower limits. Measuring the GMC properties and dynamical states, we conclude that shear is the dominant mechanism shaping the molecular gas properties and regulating SF in NGC~524. This is supported by analogous analyses of the GMCs in a simulated ETG similar to NGC~524.