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We present results of studying star-forming rings in six lenticular galaxies obtained with the narrow-band photometry in the H and [N II] 6583 emission lines using the MaNGaL tunable-filter mapper at the 2.5-m telescope of CMO of SAI MSU. The gas excitation mechanism estimated from the relation of the H and [N II] 6583 line fluxes occurred to be inhomogeneous along the ring: three outer rings have narrow segments of position angles, in which shocks waves dominate in the ring. Since the nature of the rings is most likely accretionary, the location of shock excitation in the outer rings indicates the direction of arrival of the external gas inflow. Star formation events in the rings are probably quite brief and effective: we mainly observe homogeneous sub-solar metallicity of the gas close to the level of local saturation of the gas chemical evolution in the star formation process and switching of the localization of the star-forming sites on a time scale of about 100 Myr. In NGC 932, we have caught the very beginning of the external gas accretion: there is still little of it in the galaxy, and the metallicity of the gas in the star-forming ring has not yet reached saturation. [ABSTRACT FROM AUTHOR]

Abstract—Using the MaNGaL tunable-filter photometer at the 2.5-m telescope of the Caucasian Mountain Observatory of the Sternberg Astronomical Institute of Lomonosov Moscow State University, we studied star formation in an early-type gas-rich galaxy, which was until now considered to be elliptical,—NGC 5173. The gas has probably been accreted in the recent past by the galaxy from a direction inclined to its disk. Star formation that we observe now has led in the past 400 Myr to the formation of compact massive clusters with shock excitation of gas around them—a star formation behavior corresponding to what is usually observed in the interacting Antennae-like galaxies. In combination with the almost solar metallicity of the gas, this allows us to conclude that NGC 5173 has assimilate a very gas-rich companion with a mass of at least 10–20% of its own stellar mass. [ABSTRACT FROM AUTHOR]

ABSTRACT By undertaking deep long-slit spectroscopy with the focal reducer Spectral Camera with Optical Reducer for Photometrical and Interferometrical Observations (SCORPIO) of the Russian 6 m telescope, we studied stellar population properties and their variation with radius in 15 nearby S0 galaxies sampling a wide range of luminosities and environments. For the large-scale stellar discs of S0s, we have measured simple stellar population (SSP)-equivalent metallicities ranging from the solar one down to [ Z/H ]=−0.4 to −0.7, rather high magnesium-to-iron ratios, [Mg/Fe] ≥ +0.2, and mostly old SSP-equivalent ages. Nine of 15 (60 ± 13 per cent) galaxies have large-scale stellar discs older than 10 Gyr, and among those we find all the galaxies which reside in denser environments. The isolated galaxies may have intermediate-age stellar discs which are 7-9 Gyr old. Only two galaxies of our sample, NGC 4111 and NGC 7332, reveal SSP-equivalent ages of their discs of 2-3 Gyr. Just these two young discs appear to be thin, while the other, older discs have scale heights typical for thick stellar discs. The stellar populations in the bulges at radii of 0.5 re are on the contrary more metal rich than the solar Z⊙, with the ages homogeneously distributed between 2 and 15 Gyr, being almost always younger than the discs. We conclude that S0 galaxies could not form in groups at z ≈ 0.4 as is thought now; a new scenario of the general evolution of disc galaxies is proposed instead. [ABSTRACT FROM AUTHOR]

We have studied a small sample of star-forming outer rings in unbarred lenticular galaxies by means of long-slit spectroscopy. We have determined metallicities of the outer stellar disks and of the ionized gas in the rings. While the stellar disks of the S0s are metal-poor, [Z/H] < −0.4, the gas has strictly solar oxygen abundance in all the cases. [ABSTRACT FROM PUBLISHER]