ИСТИНА

We present results of very deep long-slit spectroscopy for the stellar disks of lenticular galaxies. For the first time, the high-precision Lick indices H-beta, Mgb, Fe5270, and Fe5335 are calculated over the radius ranges of 3-12 kpc (1-4 disk scalelengths), the SSP-equivalent stellar ages and metallicities are determined. The outer disks of the lenticular galaxies have appeared to be of solar and subsolar metallicity, and most of them are rather old, with T~ 6-12 Gyr. This result is in some contradiction with the numerous studies of intermediate-redshift clusters where lenticulars start to appear only at z<0.5, or less than 5 Gyr ago, being evidently transformed from blue spirals. With our new results on the age of stellar disks in lenticular galaxies, we discuss possible origin of lenticulars under different types of environment.