Open AccessThe kinematics of lopsided galaxies
Author(s) -
Noordermeer Edo,
Sparke Linda S.,
Levine Stephen E.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.04924.x
Subject(s) - physics , astrophysics , halo , kinematics , galaxy , astronomy , disc galaxy , galactic halo , peculiar galaxy , disc , elliptical galaxy , classical mechanics
Lopsidedness is a common feature in galaxies, both in the distribution of light and in the kinematics. We investigate the kinematics of a model for lopsided galaxies that consists of a disc lying off‐centre in a dark halo, and circling around the halo centre. We search for families of stable, closed, non‐crossing orbits, and assume that gas in our galaxies moves on these orbits. Several of our models show strong lopsided gas kinematics, especially those in which the disc spins around its axis in a retrograde sense compared with its motion around the halo centre. We are able to reproduce the H i velocity map of the kinematically lopsided galaxy NGC 4395. The lopsidedness in our models is most pronounced in the models where the halo provides a relatively large fraction of the total mass at small radii. This may explain why the gas shows lopsidedness more frequently in late‐type galaxies, which are dominated by dark matter. Surfaces of section show large regions of irregular orbits in the models where the halo density is low. This may indicate that these models are unstable.