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Surface differential rotation (SDR) plays a key role in dynamo models. SDRestimates are therefore essential for constraining theoretical models. Wemeasure a lower limit to SDR in a sample of solar-like stars belonging to youngassociations with the aim of investigating how SDR depends on global stellarparameters in the age range (4-95 Myr). The rotation period of a solar-likestar can be recovered by analyzing the flux modulation caused by dark spots andstellar rotation. The SDR and the latitude migration of dark-spots induce amodulation of the detected rotation period. We employ long-term photometry tomeasure the amplitude of such a modulation and to compute the quantityDeltaOmega_phot =2p/P_min -2pi/P_max that is a lower limit to SDR. We find thatDeltaOmega_phot increases with the stellar effective temperature and with theglobal convective turn-over time-scale tau_c. We find that DeltaOmega_phot isproportional to Teff^2.18pm 0.65 in stars recently settled on the ZAMS. Thispower law is less steep than those found by previous authors, but closest torecent theoretical models. We find that DeltaOmega_phot steeply increasesbetween 4 and 30 Myr and that itis almost constant between 30 and 95 Myr in a 1M_sun star. We find also that the relative shear increases with the Rossbynumber Ro. Although our results are qualitatively in agreement withhydrodynamical mean-field models, our measurements are systematically higherthan the values predicted by these models. The discrepancy betweenDeltaOmega_phot measurements and theoretical models is particularly large instars with periods between 0.7 and 2 d. Such a discrepancy, together with theanomalous SDR measured by other authors for HD 171488 (rotating in 1.31 d),suggests that the rotation period could influence SDR more than predicted bythe models.

Lower limit for differential rotation in members of young loose stellar associations