Age and metallicity of the bulges in lenticular galaxies

Panoramic spectroscopic data of the sample of 80 nearby lenticular galaxies obtained with the Multi-Pupil Fiber Spectrograph of the 6-m telescope are presented. The SSP-equivalent ages, [Z/H], and [Mg/Fe] are determined through the Lick indices H-beta, Mgb, and separately for the nuclei and for the bulges. About a half of the sample contain chemically distinct nuclei, more metal-rich and younger than the bulges. The correlations of the stellar population properties for the nearby S0s are discussed.Comment: 5 pages, 2 figures. To appear in the Proceedings of the IAU Symposium 245, "Formation and Evolution of Galaxy Bulges", held at Oxford, U.K., July 2007, Eds. M. Bureau, E. Athanassoula, B. Barbu

Star formation in outer rings of S0 galaxies. III. UGC 5936 -- an S0 with currently accreted satellite matter

Though S0 galaxies are usually thought to be `red and dead', they demonstrate often star formation organized in ring structures. We try to clarify the nature of this phenomenon and its difference from star formation in spiral galaxies. The luminous S0 galaxy with a large ring, UGC 5936, is studied here. By applying long-slit spectroscopy along the major axis of UGC 5936, we have measured gas and star kinematics, Lick indices for the main body of the galaxy, and strong emission-line flux ratios in the ring. After inspecting the gas excitation in the ring using line ratios diagnostic diagrams and having ensured that it is ionized mostly by young stars, we have determined the gas oxygen abundance by using popular strong-line methods. Also we have proved the spatial proximity of the south-eastern dwarf satellite to UGC 5936 and have measured its gas metallicity. The ionized gas of the ring is excited by young stars and has solar metallicity. Star formation in the ring is rather prolonged, and its intensity corresponds to the current HI content of UGC 5936 (to the Kennicutt-Schmidt relation). The whole morphology of the HI distribution implies current accretion of the cold gas from the satellite onto the outer disc of UGC 5936; due to the satellite location and rotation in the plane of the stellar disc of the host galaxy, the accretion is smooth and laminar providing the favorable condition for star formation ignition.Comment: 5 pages, 5 figures, accepted for publication in A&A Letter