Lopsided galaxies: the case of NGC 891 |
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Authors: | M Mapelli B Moore J Bland-Hawthorn |
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Institution: | Institute for Theoretical Physics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland;Institute of Astronomy, School of Physics, University of Sydney, Australia |
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Abstract: | It has been known for a long time that a large fraction of disc galaxies are lopsided. We simulate three different mechanisms that can induce lopsidedness: flyby interactions, gas accretion from cosmological filaments and ram pressure from the intergalactic medium. Comparing the morphologies, H i spectrum, kinematics and m = 1 Fourier components, we find that all of these mechanisms can induce lopsidedness in galaxies, although in different degrees and with observable consequences. The time-scale over which lopsidedness persists suggests that flybys can contribute to ~20 per cent of lopsided galaxies. We focus our detailed comparison on the case of NGC 891, a lopsided, edge-on galaxy with a nearby companion (UGC 1807). We find that the main properties of NGC 891 (morphology, H i spectrum, rotation curve, existence of a gaseous filament pointing towards UGC 1807) favour a flyby event for the origin of lopsidedness in this galaxy. |
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Keywords: | methods: N-body simulations galaxies: individual: NGC 891 galaxies: interactions galaxies: kinematics and dynamics |
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