| In the first part of this thesis, we present the results of an imaging survey of an unbiased sample of early-type (S0-Sa) barred galaxies in the field. using the WIYN telescope and archival HST data. The focus of the survey was on finding and characterizing central stellar and gaseous structures: secondary bars. inner disks, and nuclear rings. Secondary bars are surprisingly common: at least one quarter of the sample galaxies (possibly as many as 40%) are double-barred. Secondary bars show no preference for Hubble type or bar strength (SB versus SAB). We find inner disks in at least 20% of the sample. almost exclusively in S0 galaxies. Nuclear rings are found in a quarter of the sample. preferentially in Sa galaxies. Most of the rings are dusty, sites of current or recent star formation, or both; only one galaxy appears to have a purely stellar nuclear ring.; The random orientation of secondary bars with respect to their "parent" primary bars suggests that they are independent structures, rotating with a different pattern speed from the main bar. We found no significant effect on nuclear activity: double barred galaxies are about as likely to harbor an active nucleus as singly barred galaxies. Two galaxies are particularly noteworthy for their multiplicity of central structures. NGC 2681 has three concentric, misaligned bars. as well as a blue nuclear ring. NGC 3945 has two bars., an inner disk, and a stellar nuclear ring.; In the final part of the thesis. we examine closed orbits and dissipational particle motion around a binary star system. We find several families of stable, off-plane orbits, one of which is easily accessible to particles orbiting in the plane of the binary motion (e.g., in a circumbinary accretion or protoplanetary disk). Some of the implications for circumbinary accretions disks and the Solar System's Kuiper Belt are discussed. |
