arXiv subjects

Linda S. Sparke

Publications and source records attributed to Linda S. Sparke.

21 records · Page 2Linked to original sources

arXiv1998

A WIYN Survey of Early-Type Barred Galaxies: Double Bars and Central Structures

We present results from a preliminary analysis of a recently-completed, multicolor imaging survey of nearby, early-type barred galaxies in the field, carried out with the WIYN telescope and supplemented with archival HST images. This forms a reasonably complete sample of nearby, bright, barred S0 and Sa galaxies in the field. The excellent seeing provided by WIYN allows us to examine the galaxies for central features such as circumnuclear rings and secondary bars; we find some evidence for dust lanes within secondary bars. The most striking results is the high frequency of double bars: our analysis suggests that at least $\sim 20%$ of barred S0-Sa galaxies possess secondary bars}. We also find an excellent candidate triply barred galaxy: NGC 2681.

astro-ph↗

arXiv1997

Regular Orbits and Periodic Loops in Multiply-Barred Galactic Potentials

We show that non-chaotic multiply-periodic particle orbits can exist in a galaxy-like potential where a small fast-tumbling nuclear bar is nested inside a main bar which has a slower pattern speed. We introduce the concept of a loop: a one-dimensional curve such that particles distributed along it at some initial instant return to the same curve (as viewed in the rotating frame of one of the bars) after the bars return to the same relative position. Just as particles following regular orbits in a simply-barred potential are trapped around closed periodic orbits, so regular orbits in a doubly-barred potential oscillate about stable loops. We find both loops which remain aligned with the inner bar and loops aligned with the outer bar: particles trapped around these loops could form the building blocks for a long-lived, self-consistent, doubly-barred galaxy. In a realistic doubly-barred galaxy potential, we demonstrate the existence of stable loops which support the structure of the inner bar. We use the epicyclic approximation to preview the pattern of gas flow in a doubly-barred potential.

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arXiv1995

The Evolution of Viscous Inclined Disks in Axisymmetric and Triaxial Galaxies

We have used a set of equations developed by Pringle (1992) to follow the evolution of a viscous twisted disk in a galaxy-like potential which is stationary or tumbling relative to inertial space. In an axisymmetric potential, the disk settles to the equatorial plane at a rate determined largely by the coefficient $ν_2$ associated with shear perpendicular to the local disk plane. If the disk is initially close to the galaxy equator, the rate at which the inclination decays is well described by the analytic formula of Steiman-Cameron and Durisen (1988); in a highly inclined disk, `breaking waves' of curvature steepen as they propagate through the disk, rendering the numerical treatment untrustworthy. In a triaxial potential which is stationary in inertial space, settling is faster than in an oblate or prolate galaxy, since the disk twists simultaneously about two perpendicular axes. If the figure of the potential tumbles about one of its principal axes, the viscous disk can settle into a warped state in which gas at each radius follows a stable tilted orbit which precesses so as to remain stationary relative to the underlying galaxy.

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