137 research outputs found
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
Two more disk galaxies with global gas counterrotation
We report a discovery of extended counterrotating gaseous disks in early-type
disk galaxies NGC 2551 and NGC 5631. To find them, we have undertaken complex
spectral observations including integral-field spectroscopy for the central
parts of the galaxies and long-slit deep spectroscopy to probe the external
parts. The line-of-sight velocity fields have been constructed and compared to
the photometric structure of the galaxies. As a result, we have revealed
full-size counterrotating gaseous disks, the one coplanar to the stellar disk
in NGC 2551 and the other inclined to the main stellar disk in NGC 5631. We
suggest that we observe the early stages of minor-merger events which may be
two different stages of the process of lenticular galaxy formation in rather
sparse environments.Comment: 8 pages, 8 EPS figures, accepted for publication in Ap
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
Current Star Formation in the Outer Rings among Early-Type Disk Galaxies
By using the ARRAKIS, the atlas of stellar rings in galaxies (Comeron et al.
2014) based on data of the S4G survey, we have compiled a list of early-type,
S0-Sb, disk galaxies with outer stellar ring-like features (`pure' rings, R, or
pseudorings, R'). Current star formation signatures within these features were
searched for through the NUV-maps of the galaxies provided by the ultraviolet
space telescope GALEX. We have found that current star formation, with the mean
age of the young stellar population less than 200 Myr, is present in about a
half of all `pure' rings; and within the pseudorings it is observed almost
always.Comment: 5 pages, 1 figure. Submitted to the Baltic Astronomy as a
contribution to the proceedings of the conference "Modern Stellar
Astronomy-2015" (Moscow, May 25-30
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