ИСТИНА

S0 galaxies are disc galaxies which lack spiral arms and are thought to lack also gas and star formation in their disks. However we detect extended ionized-gas disks in the most nearby S0-galaxies populating sparse environments. Moreover, the statistics of the multiwavelength S0 images provides evidences for the presence of star formation in their outskirts in some 30% cases; and this star formation is typically organized as ring-like structures. By undertaking deep long-slit spectroscopy, we have measured stellar population properties - ages and metallicities - in the outer stellar disks of a sample of nearby S0 galaxies and have estimated the ionized-gas metallicities in their outer rings by the strong-line method. While the outer stellar disks of the galaxies under consideration have appeared to be very metal-poor, the gas in the rings reveals solar metallicity. We discuss the possible origin of the starforming rings in the outer disks of nearby S0-galaxies.