Special Astrophysical Observatory, Nizhnij Arkhyz, Karachaevo-Cherkesia, 369167, Russia
2 Instituto Nacional de Astrofísica Optica y Electrónica, Apartado Postal 51 y 216, CP 72000, Puebla, Pue., México
Corresponding author: A. V. Moiseev, email@example.com
Accepted: 21 January 2004
Results of optical and NIR spectral and photometric observations of a sample of candidate double-barred galaxies are presented. Velocity fields and velocity dispersion maps of stars and ionized gas, continuum and emission-line images were constructed from integral-field spectroscopy observations carried out at the 6 m telescope (BTA) of SAO RAS, with the MPFS spectrograph and the scanning Fabry-Perot Interferometer. NGC 2681 was also observed with the long-slit spectrograph of the BTA. Optical and NIR images were obtained at the BTA and at the 2.1 m telescope (OAN, México). High-resolution images were retrieved from the HST data archive. Morphological and kinematic features of all 13 sample objects are described in detail. Attention is focused on the interpretation of observed non-circular motions of gas and stars in circumnuclear (one kiloparsec-scale) regions. We have shown first of all that these motions are caused by the gravitational potential of a large-scale bar. NGC 3368 and NGC 3786 have nuclear bars only, their isophotal twist at larger radii being connected with the bright spiral arms. Three cases of inner polar disks in our sample (NGC 2681, NGC 3368 and NGC 5850) are considered. We found ionized-gas counter-rotation in the central kiloparsec of the lenticular galaxy NGC 3945. Seven galaxies (NGC 470, NGC 2273, NGC 2681, NGC 3945, NGC 5566, NGC 5905, and NGC 6951) have inner mini-disks nested in large-scale bars. Minispiral structures occur often in these nuclear disks. It is interesting that the majority of the observed, morphological and kinematical, features in the sample galaxies can be explained without the secondary bar hypothesis. Thus we suggest that a dynamically independent secondary bar is a rarer phenomenon than follows from isophotal analysis of the images only.
Key words: galaxies: kinematics and dynamics / galaxies: spiral / techniques: spectroscopic
Based on observations carried out at the 6 m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences, operated under the financial support of the Science Department of Russia (registration number 01-43), at the 2.1 m telescope of the Observatorio Astronónico Nacional, San Pedro Martir, México, and from the data archive of the NASA/ESA Hubble Space Telescope at the Space Telescope Science Institute. STScI is operated by the association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.
© ESO, 2004