Stellar M/L ratio gradients of E+S0 galaxies and their implication to IMF variation

We measured the radial profile of stellar M/L ratio of CALIFA DR2 E+S0 galaxies,and found that the M/L ratio shows significant negative gradients  for all thegalaxies and in all optical bands, with steeper gradients at  shorterwavelengths. In this talk I will show those detailed properties and analyzehow this result can finally affect the known evidence of galaxy IMF variation.